An Introduction to the Study of Air Mass and Isentropic Analysis

A I^AfiTuivw.*^

By JEROME NAMIAS

Fifth Revised and Enlarged Edition with Contributions by TOR BERGERON BERNHARD HAURWITZ GRAHAM MILLAR ALBERT K. SHOWALTER ROBERT G. STONE AND HURD C. WILLETT

Edited by ROBERT G. STONE

October, 1940

E AMERICAN METEOROLOGICAL SOCIETY, MILTON, MASS.

Price $1.25, postpaid Given in Loving Memory of

Raymond BraisUn Montgomery Scientist, R/V Atlantis maiden voyage 2 July - 26 August, 1931

Woods Hole Oceanographic Institution Physical Oceanographer 1940-1949 Non-Resident Staff 1950-1960 Visiting Committee 1962-1963 Corporation Member 1970-1980

Faculty, New York University 1940-1944 Faculty, Brown University 1949-1954 Faculty, Johns Hopkins University 1954-1961 Professor of Oceanography, Johns Hopkins University 1961-1975 An Introduction to the Study of Air Mass and Isentropic Analysis

By JEROME NAMIAS

Fifth Revised and Enlarged Edition with Contributions

^5 TOR BERGERON ^S° BERNHARD HAURWITZ ^m ^ GRAHAM MILLAR x^SP ALBERT K. SHOWALTER ::i^g§ ROBERT G. STONE |^= AND ^^3 HURD G. WILLETT

Edited by ROBERT G. STONE

October, 1940 THE AMERICAN METEOROLOGICAL SOCIETY, MILTON, MASS.

Price $1.25, postpaid The Previous Editions of This Work

Appeared Under the Title

"An Introduction to the Study of Air Mass Analysis"

First Edition . . Sept., 1934-May, 1935

Second Edition . . . September, 1935

Third Edition . . . August, 1936

Fourth Edition . . . October, 1938 TABLE OF CONTENTS

Pages

Editor's Preface v-vi

Introduction . 1

I. Conditions of Atmospheric Stability: Lapse Rates . . 1-5

II. Conservative Properties of Air Masses 6-12

III. The Rossby Diagram—Plotting Routine 12-19 IV. The Rossby Diagram—Interpretation .... 20-24

V. Elements of Frontal Structure—The Warm Front . 24-28

VI. Elements of Frontal Structure—The Cold Front . . . 28-31

VII. Elements of Cyclonic Structure 31-36

The Norwegian Wave-Theory of Cyclones, by B. Haurwitz . . 37-45

Frontal Waves, by T. Bergeron 45

Sources of Energy for Extra-Tropical Cyclones, by T. Bergeron 45-46

A Note on Dynamic Anticyclones and Cyclones, by R. G. Stone 46-50

The Role of the Tropopause in the Dynamics of Extra-Tropical Disturbances, by T. Bergeron 50

VIII. The Tephigram 50-55

Radiometeorograph Soundings in the Middle North Atlantic

(after Durandin) . . 48-49

A Note on Estimating Conditional and Convective Instability FROM THE Wet-Bulb Curve, by R. G. Stone .... 55-60 IX. Synoptic Aspects of the Thunderstorm 60-68

Airplane Soundings Illustrating Convection (after Kochanski) 68-71 The Ice-Nuclei Theory of Rainfall, by R. G. Stone .... 72 Hail Forecasting (after United Air Lines) ...... 72 —

Pages

Characteristic Properties of North American Air Masses, by H. C. WiLLETT 73-108

Major Frontal and Air Mass Zones of the Earth, by T. Bergeron 108

Further Studies of American Air Mass Properties, by

A. K. Showalter ...... 109-113

Illustrations:— 113-135

Dust Storm (after Parkinson) 114-115

Flood Rains (after Minser; Byers) 116-llT

Fronts and Aircraft Icing (after Minser) .... 118-121

Bergeron's Model of the Warm-Front-Type Occlusion . 122-124

Spring Showers (after Botts) 125

Winter Cyclone with Dust ^Storm (after Parkinson) . 126-127

Maps and Cross Sections of Fronts; Aircraft Icing (after Minser) 128

A Succession of Polar Air Masses; Weather Maps and Cross Sections for Nov. 30 Dec. 2, 1938 (after George and Elliot) 129-131

A RossBY Diagram (after Tu) 131

Synoptic Charts Showing Winter Cyclones (after Pierce; Dorsey) 131-135

X. Isentropic Analysis 136-161

ISENTROPic Analysis of a Thunderstorm Situation, June 22-27, 1937 (after J. Namias) 161-167

Analysis of the Rainfall Situation over the Western States, May 6-7, 1938, by Means of Air Mass and Isentropic Charts (after Weightman) 168-171

Examples of Upper-Air Cross-Sections Showing Interpretations OP the Tropopause, etc 172-175

A Bibliography for Synoptic Meteorologists, by R. G. Stone . 176-226

Addenda to Bibliography 227

Glossary of Elementary Terms Used in Articles in I to IX . . 228-232 —

Corrigenda for "An Introduction to the Study of Air Mass and Isentropic Analysis/' by J. Namias and others, 5th ed.

Page 5, table at bottom of page, lines under "Condition" and "Type of equilibrium", should be deleted and the following should be substituted (the

preferred terminology is italicized: (Absolutely) stable a< ft a — B Neutral for saturated air (equal to wet-adiabatic lapse rate)

a = y Neutral for dry air (equal to dry-adiabatic lapse rate)

a = 3.42°/100 m Upper limit of mechanical stability

[a > 3.42 "100 m Mechanical instability, or auto-convective gradient (self starting; hence this is not an equilib-

rium) ]

Page 6, col. 2, line 8 of footnote, "J.-J. Jang" should read "Jaw." "'^" Page 14. col. 1, line 11, "r/Pi"-^ " should read "T/p.

Page 14, col. 1, line 18, "wet-bulb temperature" should read "wet-bulb poten-

tial temperature."

Page 69, line 7, "Su" should read "Sc."

Page 71, top, line 4, delete "warm."

Page 150, col. 2, line 4, "stream function" should read "isentropic accelera-

tion potential" (see Bulletin A. M. S., Jan. 1941, p. 45).

Page 172, line 18 (in fine print) "frontal at" should read "frontal topography at."

Page 174, line 9, "15 km" should read "18 km or higher."

Page 174, line 10, "by 10 mb" should read "by 9 mb."

Page 175, line 1, "In Fig. 6, shown above is" should read "Fig. 6 above is". . .

Page 175, line 3, "tions shows" should read "tions. It shows."

Page 228, 2nd col. line 34, "to dry air" should read "to saturated air;" line

33, after "entire" insert "originally stable".

Page 229, 2nd col., lines 2 and 3 from bottom, "decreases" should read "increases."

Page 232, 2nd col., 3rd line from bottom delete "equal".

[Supplement to the June 1941 Bulletin of the American Meteorological Society']

—

Editor's Preface to 5th Edition

UNCEASING demand has again correct a few typographical and other induced the Society to extend errors which unfortunately passed in this convenient booklet into the 4th edition; the editor wishes to a 5th revised and enlarged edition. The thank the numerous individuals who text of the 4th edition is reprinted with have kindly called our attention to numerous secondary annotations and errors and offered suggestions for changes to indicate some of the present improvement. The basic part of this in- attitudes or practices that depart from troduction remains rather elementary, those stated or implied in the previous but many more technical annotations editions. The practices in other coun- are provided for the numerous stu- tries are so diverse that no special note dents who have the background to of them could be taken, but extensive enter a little deeper into the subject. citations of foreign literature are However, we have not attempted to given in the Bibliography. enlarge the work into a textbook of At the time the 4th edition appeared synoptic meteorology. It is assumed (Oct. 1938) a new technique and point that the reader is familiar with the of view, known as isentropic analysis, elements of meteorology and with the was under promising experimental de- general conception of the weather velopment and it was anticipated by map as given in numerous and readily the authors and editor that any future available textbooks, to which this edition of this "Introduction" would booklet is only an adjunct of certain have to take account of the new method. newer topics not particularly well- Already in 1939 isentropic analysis was treated outside a few technical and so generally practiced in U. S. A. that expensive works. plans were laid to add an introductory The material available for direct chapter on the technique. Mr. Namias analysis of upper-air conditions has was engaged by Prof. Sverre Petter- lately reached a new high. There are ssen to prepare such a chapter for his now 34 regular aerological stations in excellent book "Weather Analysis and the U. S., mostly using radiosondes, Forecasting" recently published. We the largest network of its kind in the are able to offer a slightly modified world and in history. The adequate form of this chapter in our 5th edi- use of such data in forecasting is being tion, through the kind permission of tried here for the first time anywhere Prof. Petterssen and of the McGraw- and will call for an increasingly quan- Hill Book Co., Inc., of New York. titative and physical approach. The Bibliography in the 4th edition The editor wishes to acknowledge has been so widely appreciated that an the very generous assistance in read- effort is made to improve it materially ing proof and valuable advice on in this new edition. Besides bringing many points given by Prof. Charles it down to date, a great many more F. Brooks, Secretary of the Society, entries are added and the whole ar- who has handled the arrangements ranged conveniently by subjects. for publishing this work. Thanks are Finally, additional illustrations are due Miss Edna Scofield for aid in provided in the appendix. editing and reading proof. Robert G. This opportunity has been seized to Stone, Sept. 1940. From the Preface to the 4th Edition

When these sketches were first pre- of airport and city offices of the pared it was thought that the sub- Bureau, and many of their personnel ject would develop so rapidly that can now produce or interpret analyses any attempt to simulate a well- acceptably, while at the Central Office rounded and comprehensive treatise, in Washington competent and funda- even for beginners, would not be mental research is being carried on. justified nor feasible. Needless to say (The problem of rapidly training a the continued warm response and wide large organization in such a different influence which the work has had has technique is admittedly difficult). left the authors and editors with a The present "Introduction", how- sense of responsibility for which they ever, should not be regarded as one to had not bargained. The authors feel the whole field of synoptic meteor- that most of the early principles of ology. For such a serious ambition air mass analysis still bear a funda- one should study physical meteorology mental value for synoptic practice, so as well, and there are excellent gen- that extensive revisions have not been eral texts such as Humphreys' "Phys- necessary in this new edition, though ics of the Air", Brunt's "Physical and references are made here and there to Dynamical Meteorology", Taylor's some of the points that have been "Aeronautical Meteorology", "Byers' particularly altered or questioned in "Synoptical and Aeronautical Mete- light of more recent developments. orology", [and now (1940) also Pet- From the practical point of view, terssen's "Weather Analysis and the beginner in America now has Forecasting", Sutcliffe's "Meteorology much better opportunities to "pick up" for Aviators", and "The Admiralty experience through his own efforts Weather Manual",] to lighten the than when this "Introduction" first road. But to that large audience appeared over three years ago, when which desires only a brief, authorita- no competently analyzed air-mass tive, and inexpensive "first reader" weather maps were available outside in this fascinating concrete way of of a few institutions and special serv- looking at the weather, this booklet ices and none to the public. At pres- is offered again in the hope that ent, thanks to the remarkable changes it will continue the instrument for in U.S. iWeather Bureau practice wide dissemination of modern me- since 1934, such maps may be in- teorological principles which it has spected by anyone at a large number been.—Robert G. Stone, Oct. 1938. An Introduction to The Study of Air Mass and Isentropic Analysis By Jerome Namias Introduction to the 5th Edition THE SYSTEM of weather analysis vanced physics and mathematics. Since developed chiefly by the Norweg- weather forecasting is still quite re- ian school of meteorologists and nioved from the quantitative stage, referred to as "Air Mass Analysis" in and since a qualitative evaluation of the United States, has received wide- the various entering factors consti- spread adoption throughout the me- tutes a large share of the forecaster's teorological services of the world. In technique, it is possible to develop a addition to the group of professional moderate degree of forecasting ability meteorologists who employ these with an understanding of the physical methods as the foundation of their processes as described in these articles. activities in synoptic meteorology, The actual technique of air mass and there has developed a large group of isentropic analysis can hardly be im- people whose interests are so intimate- parted adequately by written material. ly associated with meteorology that It It requires a more personalized guid- is necessary for them to possess more ance by an experienced analyst. than a fragmentary knowledge of the While textbooks in modern synoptic physical processes of the atmosphere. meteorology have been vastly improved The increasing number of aviation since many of these articles were first enthusiasts is only one of these groups. written, notably by the works of Byers, Many such people, and indeed, many Taylor and Sutcliffe, there has con- practicing professionals at present en- tinued a demand for these articles, and gaged in meteorology, have not had the more recently for some similar presen- time nor the opportunity to carry on tation dealing with the new method of an organized collegiate program of upper-air analysis along the surfaces study in modern synoptic meteorology, of constant entropy. Professor S. Pet-

and for this reason have felt the need terssen (of M. I. T.) and the McGraw- for some simplified presentation of the Hill Company have been so kind as to fundamentals upon which the science permit me to publish here, with some rests. It has been the purpose of this small alterations, the chapter on series of articles to fulfill this gap in isentropic analysis originally prepared such a manner that these students may for his textbook on Weather Analysis be able to obtain a physical picture of and Forecasting (McGraw-Hill, N. Y., basic weather processes without first 1940). having to possess a mastery of ad-

I. CONDITIONS OF ATMOSPHERIC STABILITY: LAPSE RATES A. Vertical Displacement of through expansional cooling of rising A Particle air. It can be shown that the amount It has long been known that verti- of precipitation possible through the cal motions in the atmosphere are of mixing of currents of air possessing great significance in that practically different temperature and moisture all precipitation may be ascribed to characteristics is very small, and the condensation brought about that the precipitation resulting from AIR MASS ANALYSIS

this cause must be negligible in com- 3. Neutral parison with other causes. Further- a. With respect to dry air more the theory of fronts and air b. With respect to saturated air is based upon atmospheric masses 4. Conditional discontinuities, which . are simply Another case, that of convective zones of rapid transition of the vari- equilibrium, will be treated inde- ous meteorological elements. It is pendently in a future article, since it assumed that these zones of transition concerns the displacement of layers are comparatively free from large of the atmosphere rather than the dis- scale mixing, the individual large placement of individual particles of scale air currents flowing side by side air through a given layer. or above one another without appre- It is obvious that if a particle of air ciable mutual drag. is lifted it must expand against the Granting the importance of vertical decreasing pressure so that the pres- motion in the atmosphere a discussion sure within and surrounding the par- of the factors which tend to aid or ticle must be equal ; if it sinks it must hinder such motion is in order. This be compressed. It is assumed that leads to the problem of stability. these changes take place without the Here the term stability is used in its transfer of heat either from the mov- physical sense; if an air particle ing particle to its surroundings or tends to remain in, or return to, its vice versa. Such a thermally insul- former position following a displace- ated process is termed adiabatic. If ment, the condition is termed stable; the particle expands it does work; if if displacement results in a tendency it is compressed work is done upon to further movement of the particle it. Thus there must be a conversion from its original position, the origi- of mechanical energy into realized nal condition is designated as un- heat if the particle sinks, while heat stable; and finally, if the particle must be converted into mechanical neither resists nor assists displace- energy if the particle rises. By ment, the condition is one of neutral means of thermodynamics it can be equilibrium. shown that the relation between tem- B. Types of Equilibrium perature and pressure in an adiabatic displacement of an unsaturat- In the case of the atmosphere there ed particle is as follows: are four principal types of equilibrium to be considered when we are concerned with the vertfcal displacement ^(^) of a selected particle through a layer where is the original temperature of the atmosphere having known Ti of the particle at the pressure and characteristics. These types of equi- pi, librium are: Ti is the temperature it assumes at the pressure ?>2. This is Poisson's 1. Stable equation. a. With respect to dry air^ It is generally more convenient in b. With respect to saturated air aerological studies to refer to the adi- 2. Unstable abatic changes in temperature with a. With respect to dry air respect to changes in elevation. From [1. Mechanical] ^The term "dry air" in synoptic meteorol- b. With respect to saturated air ogy simply means unsaturated air. LAPSE RATES

Poisson's equation and the hydro- lapse rate, or dry adiabat. (Lapse static equation (expressing the rela- rate is defined as the rate of change tion between pressure, density, and in temperature with respect to height. height), it is possible to obtain the Unless preceded by the qualifying rate of cooling of a rising air parti- term "adiabatic," lapse rate refers to cle owing to its change in elevation. the existing difference of temperature The result is the convenient rate of per unit of height within a selected 1 C deg, per 100 m. This rate is not layer of the atmosphere.) strictly constant; it depends upon Thus far we have considered the the amount of moisture within the vertical displacement of an unsatur- unsaturated air particle as well as ated particle of air. Once the parti- the temperature of the surrounding cle becomes saturated the latent heat air through which it is displaced. of condensation must be taken into However, these effects are relatively account, for it supplies heat to the small and tend to counteract each rising mass and therefore lessens the other. Hence, for all practical pur- rate of cooling due to expansion. The poses, they may be neglected, the adi- lessening of the adiabatic cooling ef- abatic rate of change of temperature fect depends upon the liberated heat being taken as 1 C deg. per 100 m. of condensation, which in turn de- change in elevation. This is com- pends upon the amount of liquid wa- monly known as the dry adiabatic ter condensed. But as the particle

temperature c Fig. 1. Types of Lapse Rates AIR MASS ANALYSIS

continues to rise, its temperature always to make the particle return falls, so that the total quantity of wa- to its original position. It is clear ter vapor possible within the volume then that the line ai represents a of rising air becomes less and less. stable lapse rate. In other words if Therefore the rate of cooling of the the lapse rate is less than the dry saturated mass becomes greater and adiabat the layer is stable for un- greater, until at high levels, where saturated air. the moisture content of the rising air The rate of adiabatic cooling for a

is almost negligible, its 'rate of adi- rising saturated particle of air is abatic cooling is practically the same represented in fig. 1 by the line ^. as that for dry air. Note that ^ is a curved line, since We are now prepared to deal with the rate of cooling is dependent upon the types of equilibrium as outlined the heat of condensation as well as above. upon the expansion. Also note that

the curve jS tends to straighten, 1. Stable. The rate of cooling for gradually approaching the slope of an unsaturated particle of air rising y at upper levels, where the moisture through the surrounding atmosphere content becomes smaller and smaller. is given by the broken line y in fig. If we now assume a lapse rate of a^ 1. This is a straight line since the from 1 to 3 km. it is clear that a ris- rate is 1 C deg. per 100 m. Lines ing particle of saturated air will fol- drawn parallel to y would represent low the line R, and will at every stage other dry adiabats at different tem- in its ascent be colder than its sur- peratures. If we assume the ob- roundings. Thus it will tend to reserved vertical temperature distribu- main at its original position and the tion (the lapse rate) above 1000 m to layer between 1 and 3 km. will, by be represented by the line ai, it is at definition, be termed stable with re- once clear that a particle of air taken spect to saturated air. A lapse rate from any position on the line ai and less than the saturated adiabat may brought up or down will immediately be termed absolutely stable since it is find itself of a different temperature stable whether the rising air be dry and hence different density from its or saturated. surroundings. It will consequently tend to return to its original position. 2. Unstable. Let us assume that For example let us take a particle at the lapse rate between 1 and 2 km. 1000 m. where the temperature is 20° has the form as as in fig. 1. A parti- C. If we bring this particle up to cle of air displaced upward from any line would follow 2000 m., it will follow the line y and position on the as at 2000 m. will assume the tempera- parallel to the dry adiabat y and ob- ture 10° C. The surrounding air at viously would be warmer than the 2000 m., however, has the tempera- surrounding air, level for level. There- ture 14° C, or 4 deg. warmer than fore it would continue to rise. The the rising particle. Under this con- layer possessing the lapse rate aS is dition the particle must return to its then unstable with respect to dry air, former position, coming to rest at and since the saturated adiabatic 1000 m, where its temperature is the lapse rate is always less than the dry, same as the surrounding air. In a it is clear that this condition is even similar fashion it is easily shown that more unstable for saturated air. The downward motion of individual parti- line as has been constructed to rep- cles originally lying along the line resent a special case of instability in ai are hindered, the tendency being which the density remains constant —

LAPSE RATES 5 with elevation. The density, of course, cle will possess the temperature of is a function of the temperature and the surrounding air at every stage in pressure, and is slightly affected by its ascent. Thus it will neither as- the moisture content. In the atmos- sist nor resist displacement. If the phere the pressure decrease with ele- rising air is saturated then the con- vation is such that it nearly always dition for neutral equilibrium re- overbalances the increase in density quires that the lapse rate equal the caused by the usually observed drop saturation adiabat. If in temperature with elevation. the i. Conditional equilibrium. It was temperature falls off sufficiently rap- pointed out that the lapse rate given idly with elevation, however, a state by the line ai is stable for rising air, will be reached wherein the density while between 1 and 3 km. it is un- of the air is constant with height. If stable for saturated air, because the the lapse rate exceeds the value 3.42 lapse rate ai lies between the saturat- C deg. per 100 m there must be an ed and the dry adiabat. When this increase in density with elevation state obtains the layer is said to be obviously a very unstable condition. in conditional equilibrium. The con- This particular case has been given dition is simply that the layer is un- various names, the best one probably stable if saturated, but stable if un- being mechanical instribility. as rep- saturated. This lapse rate is fre- resents a state of mechanical insta- quently observed in aerological sound- bility. This condition is never ob- ings, and has been found to be impor- served in the upper atmosphere, since tant in the development of thunder- it is such an unstable state. It is, storms and showers. It should be however, frequently observed imme- noted that the conditional instability diately overlying flat regions which in the case of fig. 1 extends through become greatly heated during the the layer between 1 and 8 km., and summer daytime hours. no higher. Beyond 3 km. the lapse

In the case of instability wdth sat- rate oa does not lie between the dry urated air the lapse rate must be adiabat and the saturated adiabat for greater than the saturated adiabat. the temperatures at these elevations. In fig. 1 the line ai represents such The rate of change of temperature a lapse rate between 1 and 3 km. It along the line yj (above 3 km.) is should be noted that the layer above greater than along the line ai. 3 km. is not unstable for saturated A summary of the above conditions air, since the rate of change of the is presented in algebraic form be- temperature along ai above 3 km. is low: where a represents the existing less than that along p. rate of change in temperature with 3. Neutral equilibrium. With dry elevation (the lapse rate) ; y, the dry air this state is reached when the adiabatic lapse rate; the fi, the satur- lapse rate is equal to the dry adiabat. ated adiabatic lapse rate. Under this condition the rising parti- Covdition Type of equilibrium a B Unstable for both dry and saturated air a — V Neutral for dry air a= B Neutral for saturated air B 3.42° C per 100 m. All air is mechanically unstable (density in-

creases with height) ; "auto-convective gradient". —

AIR MASS ANALYSIS

11. CONSERVATIVE PROPERTIES OF AIR MASSES

An air mass is defined as an exten- low layers and by radiation chiefly sive body of air which approximates from the surface of the new region horizontal homogeneity. The proper- over which the air mass is traveling. ties of the air mass which are con- The theory of air masses as entities sidered in this homogeneity are mainly is based upon the fact that the varia- temperature and moisture. Thus over tions of any property in the horizon- the earth's surface one may observe tal in an air mass are small compared large currents of air within which the with the rapid change of properties temperature and moisture content re- observed at the boundary between two main fairly constant at any given air masses which come from different level. These large scale currents of source regions. This boundary zone air have their origin at a source re- of rapid transition is a front. gion—a large area characterized by From the definition of an air mass sameness of surface conditions and it is clear that in order to identify evenly distributed insolation. Thus the sections of a current as belonging to northern part of Canada in winter one and the same air mass we must may be considered as a source region not only know the properties at the in that it is practically snow-covered, source region and the modifications in- and the amount of insolation received troduced, but we must also deal with is almost evenly distributed over the observations which are most repre- entire area. A large body of air sentative of these properties. The which remains over a source region a most representative observations are sufficient length of time assumes cer- those made by means of upper air tain definite properties in the vertical, soundings; at the surface the most particularly with respect to tempera- representative observations are those ture and moisture. Once these prop- made at elevated and exposed sta- erties have been attained, equilibrium tions. Examples of non-representa- with respect to the source region is tive observations are those of valley reached, and any further stagnation stations, or those greatly affected by or movement of the body of air over the proximity of a lake or perhaps a the source region will not appreciably mountain barrier. In the latter case affect the balanced distribution.* It is there might be an appreciable foehn clear, however, that any movement of effect. the air mass away from its source As an air mass progresses numer- region will result in a modification of ous changes take place, brought about its properties. For example, if a body by radiation, mixing (turbulent ex- of air from northern Canada moves change), adiabatic expansion or com- southeastward into the United States, pression, and condensation or evapor- there is bound to be some warming ation. Some meteorological elements and moistening. Such modifications will remain more constant than others tend to destroy the homogeneity orig- as the air mass moves from point to inally established at the source re- *The processes by which air masses reach gion. It is obvious that the modifica- homogeneous equilibrium in their source re- tion will take place essentially within gions are not yet well understood ; further discussion of this appears in the Appendix by the lowest layers of the air mass, the Prof. Willett on the air mass properties ; a upper layers being modified only grad- recent study by Wexler (Mo. Wea. Rev., April, 1936) discusses the origin of Polar conti- ually by means of the indirect pro- mental air, and J. -J. Jang has studied the formation marine air in the trade cesses of mixing with the modified of tropical winds ( see Bibliog. ) . Ed. —

CONSERVATIVE PROPERTIES OF AIR MASSES

point. Furthermore, quantities indi- the quantity of moisture subtracted rectly obtained by calculation from by condensation involves a certain loss the observations will vary in con- or gain of heat which is implied in stancy. The relative degree of con- the definition of equivalent tempera- stancy of a meteorological quantity ture. within a moving air mass is defined Evaporation does not greatly change as its conservatism. the equivalent temperature; but this We are now in a position to test is not an important limitation for our the meteorological elements and the practical purpose*. in(ilrectly calculated quantities with Changes in the temperature of a respect to their degree of constancy particle by means of expansion or (conservatism) as the air mass moves. compression (adiabatic changes) may be eliminated by the A. Temperature. use of the potential temperature. Potential tempera- The temperature of any given par- ture is that temperature a parcel of ticle of air within a moving air mass air would have if it were brought is influenced by the following factors: adiabatically to a pressure of 1000 mb. 1. Conduction and mixing. If a dry particle were vertically dis- 2. Condensation and evaporation. placed it would warm or cool at the 3. Expansion and compression dry adiabatic rate, and therefore its (adiabatic changes). actual temperature would differ from 4. Insolation and radiation. its potential temperature by about Temperature, particularly at the 1 C deg. per 100 meters from the surface, is so much changed by these level where the pressure is 1000 mb. factors that it cannot be regarded as This holds only in the event that the very representative a element by air particle remains unsaturated, for which to identify an air mass after as soon as it becomes saturated, latent it has moved away from the source heat of condensation is realized and region. the particle no longer follows the dry effect of The condensation may be adiabat, but the saturated adiabat. eliminated by the use of a quantity This was pointed out in the first art- called equivalent temperature.* This icle of this series. During ascent, is defined as the temperature a parti- therefore, the potential temperature cle of air would have if it were made of the saturated particle will increase to rise adiabatically to the top of the by virtue of the latent heat of con- atmosphere in such a manner that all densation. the heat of condensation of the water The most conservative thermal vapor were added to the air and the quantity is the equivalent-potential sample of dry air were then brought temperature. This is the tempera- back to its original pressure. Numeri- ture the chosen air particle would cally this is not much different from have if it were brought adiabatically the temperature the mass of air would to the top of the atmosphere so that have if all its moisture were made to along its route all the moisture were condense and the heat given off by condensed (and precipitated), the la- condensation were added to the re- tent heat of condensation being given maining dry air. Any change in the to the air, and then the remaining dry moisture content of the air mass by condensation will not affect the equiv- Footnote on equivalent-potential temperature on next alent page also applies to the equiva- temperature of a particle, since lent temperature. B. G. S. 8 AIR MASS ANALYSIS sample of air compressed to a pres- aloft changes because of extensive sure of 1000 mb. The equivalent-po- rising or sinking movements. In spite tential temperature may also be de- of variations in the lapse rate in the fined as the potential temperature of surface layers, the lapse rate is often the equivalent temperature; that is, it indicative of the trajectory of the air can be determined by finding the current, for when moving over a cold equivalent temperature, then reduc- surface the low layers of the current ing this adiabatically to a pressure of tend to become more stable, whereas 1000 mb. The equivalent-potential when constantly moving over a warm- temperature combines the processes er surface the lapse rate becomes involved in the definition of the po- steeper. Characteristic types of tential and the equivalent tempera- clouds are commonly associated with ture; hence it is independent of any certain lapse rates. to expansion or compres- efi:'ects due C. Humidity as well as condensation*. If sion The use of aerological material is equivalent-potential we deal with the becoming increasingly important for particle then the temperature of a the investigation of synoptic meteoro- change its value only processes which logical problems, especially when air mixing, are (1) conduction and (2) mass and frontal methods are applied. insolation and evaporation,* and (4) The correct identification of individ- and (4) obviously radiation. (1) ual air masses is greatly facilitated in the sur- have their maximum effect by the utilization of certain quanti- face layers, and are probably much less important at higher levels. There- *The equivalent-potential temperature defined by Rossby is not perfectly conservative fore the thermal properties of an air for an evaporating process, such as when fall- more conservative at ing precipitation is evaporated into dry air mass are far or a fog is dissolved, though the effect does upper levels than in the low layers. not change the equiv.-pot. temp, greatly. However, as Bleeker has pointed out (Q. Jn, Consequently it is best to use upper Roy. Met. Soc, Oct. 1939), misleading con- surface observa- clusions as to air-mass identity and move- air data rather than ments can be made from the e.-p. temp, if tions as criteria for the determination evaporation takes place. The thermodynamic properties which are conservative for evapora- and identification of air masses. tion are not conservative for adiabatic changes Rate. and condensation ; there is, in fact, no ele- B. Lapse ment which is conservative for all conceiv- The lapse rate associated with an able changes of the air. In Germany Rossby's equivalent potential temperature is also known air mass is frequently a good index as the "pseudo-potentielle Temperatur" (Stiive). Another quantity differing from in the for identification purposes. As Rossby's but sometimes referred to as the case of thermal quantities, the lapse "equivalent potential temperature" (Normand, 1921) and "equi-potentielle Temperatur" (Ro- rate is much more conservative at bitzsch, 1928), is conservative for evaporatior> but not for adiabatic processes and condensa- upper levels. In the surface layers tion ; it is defined as the temperature that the lapse rate will be found to vary would result by condensing out all the water vapor but at a constant pressure of lOOO appreciably from day to day, and mb. This of course does not give the same result as when an air mass is raised from nighttime to daytime. These adiabatically to lower temperatures (and low- effects are mainly the result of radia- er pressures), as in Rossby's definition. Strictly speaking the Norma nd-Robitzsch tion and turbulence. For example, in quantity is an isobaric equivalent-potential temperature, whereas the Stiive-Rossby quan- hours there is apt the early morning tity is a dry-potential adiabatic equivalent to be a ground inversion, while dur- temperature, and the corresponding equivalent temperatures should be distinguished likewise. ing the afternoon an adiabatic lapse Prof. Petterssen in his new book has intr-o- duced the terms pseudo-equivalent, and pseudo- rate may extend up to about 800 wet-bulb potential temp., etc., for the adiab- meters. At higher levels surface ef- atic quantities. Such terminology is too cum- bersome in practice but it is well to understand fects are comparatively small, but the differences, as the literature and practice are very loose and misleading about these con- lapse rate there are times when the cepts.—iZ. G. S. CONSERVATIVE PROPERTIES OF AIR MASSES

ties w^hich remain about constant as the total. The correction for the tem- the air mass moves from point to perature of the surrounding air is also point. Chief among such conserva- relatively small. Accordingly the dry tive quantities is the specific humid- air is the governing factor in the adi- ity—a term which is seldom defined abatic rate of cooling of unsaturated in the elementary American text- air. Practically this amounts to say- books on meteorology, and which, ing that the volume occupied by the prior to the adoption of air-mass vapor and its temperature at any analysis, was almost completely ig- stage are essentially the same as that nored by synoptic meteorologists. In of the dry air mass with which the consideration of this it will be of in- vapor is associated. terest to review, qualitatively and in This facilitates a discussion of the brief fashion, the definitions of hygro- variations of hygrometric quantities metric terms and their relative degree in the case of ascending and descend- of constancy when an unsaturated air ing motion. particle containing some water vapor 1. Vapor pressure (e). This term is subjected to vertical displacement. represents the partial pressure ex- The vertical displacement of an air erted by the water vapor molecules particle in the atmosphere brings in the atmosphere. As an unsaturated about changes in the pressure, since particle of air is brought upward at any point the pressure within and it expands. This expansion is ef- surrounding the particle must be fected by a change in pressure equal. If it rises work must be done and a change in temperature which in expanding against the decreasing it has been shown is due to the pressure; if it descends work is done pressure change. The adiabatic tem- upon it. This work is realized as a perature change acts volumetrically change of temperature of the verti- in the opposite sense to the pressure cally moving particle. If no heat is change, since decreasing temperature added to or substracted from the mov- causes a contraction of volume. The ing element, in other words if the net effect of these two opposing fac- particle remans thermally insulated, tors is an increase of volume, so that the process is termed adiabatic. The the original amount of water vapor rate of temperature change with alti- present within the sample of air must tude of an unsaturated air particle fill a larger space. Hence the vapor due to these adiabatic changes is very pressure (e) decreases with adia- nearly constant (about 1° C. per 100 batic expansion.

m. ) , although there are small varia- 2. Relative huimdity (/). This tions in this constant due to the water term is defined as the ratio of the ac- vapor content and the temperattire of tual vapor pressure (e) and the maxi- the surrounding air in which the par- mum vapor pressure (em) possible at ticle is moving. The first of these the same temperature. It should be •corrections, that for the presence of noted that this maximum vapor pres- water vapor, becomes manifest when sure, em, is a function of temperature one considers the difference in the only and has nothing to do with at- specific heats of dry air and of water mospheric pressure. An tmsaturated * vapor. The correction, however, is air particle rising rapidly through very small, since the percentage of the atmosphere must cool nearly adi- water vapor within a unit mass of abatically and therefore the maximum air rarely exceeds a few percent of possible water vapor pressure, em, —

10 AIR MASS ANALYSIS must become smaller and smaller. water vapor and the total mass of air Since the vapor pressure within the remain constant. Hence the specific air particle (e) is also decreasing, the humidity, which depends on these two variation in the relative humidity masses, also remains unchanged. (e/em) really depends upon the rate Thus the air particle has the same of change of both these quantities. It specific humidity in spite of its rise. so happens that the rate of decrease The significance of this constancy in the denominator, that is, the falling becomes apparent when one considers off of em due to adiabatic cooling, is the active overrunning of warm air much greater than the rate of de- over a cold wedge (a warm front), crease in the vapor pressure, the nu- forced vertical displacement by an merator. Thus the percentual value advancing wedge of cold air, or the of the fraction, defined as the relative sinking of air layers within a cold air humidity, must increase as the parti- mass or in a stagnating anticyclone. cle rises.f In all these cases vertical movements in vapor pres- 3. Absolute humidity. This quan- bring about changes relative tity is defined as the mass of water sure, humidity, and absolute vapor present in a given volume, or in humidity of the vertically moving other words the density of the water particle. The specific humidity, how- vapor. Again subjecting the air par- ever, does not change, providing no ticle to adiabatic lifting it is obvious moisture is added to or subtracted precipitation, that the volume of air is increasing as from the air through the particle rises. Yet the number of evaporation, or turbulent exchange. water vapor molecules within the sam- At the surface of the earth the ple of air remains constant, so that the moisture content depends upon the density of the vapor, or the absolute synoptic air mass present and the humidity, must decrease with adia- modification which it has undergone batic expansion. during its history. Since the modification is generally greatest in the 4. humidity This Specific (q). lowest layers of the atmosphere it is defined as the mass of wa- quantity follows that the meteorological ele- a unit mass of ter vapor present in ments within these layers are less unit of air is consid- air. The mass conservative than at higher levels. usual ered as being made up of the Nevertheless, the proximity of our gas mixture plus the water vapor. The American air-mass source regions, and vapor, however, is amount of water the marked difference in our air-mass negligibly small when compared with properties* bring about considerable of air which it is the mass dry with contrast in the elements even within the ratio, associated. Hence mixing the surface layers. The specific hu- defined as the mass of water vapor in dew-point temperature a unit mass of dry air, and conven- tiVoie; In U. S. the is reported in the airways hourly observations, ient for certain theoretical calcula- and also in the six-hourly reports from first- order stations, for the humidity element ; it is- tions is very nearly numerically not strictly conservative when changes or but is use- equivalent to the specific humidity. In- differences of pressure are involved, ful for local comparisons and for fog fore- deed errors in hygrometry in aerologi- casting. R. G. S. *For a thorough treatment of these proper- cal soundings are generally much ties see "American Air Mass Properties" by in Oceano- greater than the difference between H. C. Willett, Papers Physical graphy and Meteorology, Mass. Inst, of Tech. the two quantities. and Woods Hole Oceanographic Institution. Vol. 2, No. 2, 1933 now out of print but As the unsaturated air particle as- largely reprinted in back of this booklet. Ar- ticles on air mass properties in other coun- cends adiabatically, both the mass of tries are listed in the Bibliography. CONSERVATIVE PROPERTIES OF AIR MASSES 11 midity at the surface offers a worth- be chosen arbitrarily (providing both while aid to the identification of indi- 9,re expressed in the same unit) since vidual air masses as well as in the they constitute a ratio. air. In winter the specific hu- upper D. Condensation Forms. midity at stations on either side of a The type of cloud formation is well marked front may differ by ten largely a result of the vertical dis- grams per kilogram of air. Although tribution of temperature (the lapse it is true that with large specific hu- rate) and moisture. Since both these midity contrasts at a frontal zone one quantities are fairly conservative, it generally finds good temperature con- follows that certain condensation trasts, there are many cases in which forms are more or less characteristic the temperature immediately after a of each type of air mass. Care must front passage changes but slightly be exercised in differentiating be- with the wind shift, yet the specific tween clouds formed within an air humidity changes considerably. This mass and those formed by the inter- is particularly true in summer in con- action at the front between two dif- nection with air masses of continen- ferent air masses. In addition, local tal characteristics v/hich displace condensation forms, such as ground maritime air masses. As an example fogs, must be eliminated. of this type of front a case may be cited in which a Tropical maritime air E. Visibility. mass over New England was dis- The visibility in the lower layers of placed by an older transitional air the atmosphere is generally an indi- mass originally of Polar Pacific ori- cation of the lapse rate therein. If gin. At Boston the specific humidity the lapse rate is stable, then smoke within the tropical air mass averaged and dust tend to remain close to the about fifteen grams per kilogram. surface; if the lapse rate is steep With a shift of wind from south-south- then vertical motion is easily possible west to southwest the specific humidi- and the foreign matter diluted by be- ty fell fairly rapidly to ten grams per ing mixed throughout a layer of con- kilogram, even though the tempera- siderable thickness, thereby increas- ture rose a few degrees Fahrenheit. ing the visibility in the surface layers. It cannot be doubted that the addition In cold masses which are moving of the specific humidity to the data on over a much warmer surface a steep our daily weather maps would facili- lapse rate is soon established and vis- tate the analysis and might be the ibilities become good. On the other deciding factor in the correct place- hand, when a warm current moves ment of a front when other indica- over a much colder surface the marked tions are not pronounced. stability keeps the foreign matter The numerical value of the specific concentrated in the lower layers mak- humidity is readily calculated by use ing the visibility poor. As an index of the approximate formula of the air mass present, visibility q = 622 e/v must be used with considerable care, where q represents the specific hu- since there are numerous factors other per kilo- midity expressed in grams than turbulence affecting visibility. gram; e, the existent vapor pressure Direction and Velocity. (obtained through the relative hu- F. Wind midity and temperature observa- Wind direction and velocity are in themselves not very conservative ele- tions) ; and p, the total atmospheric pressure. The units for e and p may ments. Polar air masses are fre- :

12 AIR MASS ANALYSIS

quently observed with winds having a the thermal and hygrometric quanti- southerly component, and tropical air ties are the best indices to be used in masses not infrequently have sections following and identifying air masses. in which the wind may blow from the Of these, the equivalent-potential tem- northwest. This is true particularly perature is the most conservative, in upper levels. In the placement of combining the conservative qualities fronts, however, winds are very im- of both the potential temperature and portant. Some of the fundamental the specific humidity. The above dis- concepts of this phase of the problem cussion, necessarily brief and sketchy, will be taken up in a later article in will enable us to take up the Rossby- this series. diagram in the next article of this Of the six elements named above. series.

III. THE ROSSBY DIAGRAM—PLOTTING ROUTINE

It is of primary importance in ity. Potential temperature is the synoptic meteorology that air masses ordinate of the diagram, specific hu- be followed as they move from area midity the abscissa. Since the equiva- to area over the earth's surface; the lent-potential temperature is a func- weather at any given locality is, of tion of potential temperature and course, largely dependent upon the specific humidity, another set of type of air mass present and the lines representing constant equivalent- modification which the body of air potential temperature may be con- has undergone during its history. In structed on this diagram. The sig- the preceding article it was pointed nificance of these lines as well as the out that the use of representative interpretation of various curves on observations is necessary for the the Rossby diagram will be discussed identification of air masses from later. At present we shall concern different source regions. The upper ourselves with the mechanical pro- layers of the atmosphere being com- cedure of constructing, on these dia- paratively free from surface effects, grams, curves representing aerolo- it is best to use data from upper gical soundings. air soundings. It was also shown that In the first article of this series it the most conservative quantities that was pointed out that, in an adiabatic can be used for purposes of identifi- process, the relation between tempera- cation are not the ones directly meas- ture and pressure is given by the urable—temperature and relative hu- formula midity —but those indirectly obtained T^ / 'n, \ 0.288 —potential temperature and specific humidity. These two quantities, as (-^y will be seen later (Article X), are where Ti is the temperature at the also used in isentropic analysis. pressure pi, and T-2 is the tempera- Realizing the importance of a quan- ture the particle assumes at the pres- titative method for identifying air sure P2. If we now specify that the masses, Professor C.-G. Rossby, of the particle, originally at temperature Ti Massachusetts Institute of Technol- and pressure pi be compressed to ogy, developed the diagram which 1000 mb pressure we have bears his name. As might be sup- T. 0.288 posed, the diagram makes use of the most conservative quantities—poten- \ 1000 / tial temperature and specific humid- But if the particle is reduced dry —

ROSSBY DIAGRAM PLOTTING ROUTINE 13

adiabatically to 1000 mb, the tem- reference, fig. 2 will serve to show the perature, T2, which it assumes at essential features of this diagram. this pressure is by definition the The ordinate consists of the pressure, potential temperature, wliich we shall which, in the latest type of adiabatic call 6. Thus chart, is plotted to the power 0.288 (i.e., pO.288 is the ordinate). The T. 0.288 reason for using pO.288 is that when \ 1000 / plotted in this fashion against a linear scale of lines .288 temperature, the ov 6=T, representing dry adiabats become slanting straight lines (though they From this formula the potential converge upward slightly). This is temperature is readily computed. seen from Poisson's equation. In the

^ .288 older Stiive adiabatic chart the pres- Tables giving the factoi sure is plotted on a logarithmic scale, so that there is a slight curvature to may be constructed to facilitate this the dry adiabats.* computation. In practice, however, A little manipulation of Poisson's it is generally more convenient to equation explains the other features of obtain the potential temperature by *Various older forms, such as the Hertz, means of the adiabatic chart. It is Neuhoff, and early Stiive diagrams, are still found in many physics and meteorology texts. assumed that the reader has access The more convenient form, Stuve's newer to such a chart.* For convenience of psuedo-adiabatic chart, is now used by most meteorologists and weather services. Ed. p mb. 500

\ X 14 AIR MASS ANALYSIS

the chart. One can derive that pi°'^^^ chart and definitions which have been = Ti (1000)"-'V^ and thus pi'-'"' given, the student should be able to varies only as T^; 6 and (1000)°-''' be- deduce the following important gen-

ing constants for any individual line eralizations : starting at 1000 mb. Thus T is linear 1. The potential temperature along p"''^^ •on the abscissae scale, and is a dry adiabatic line is constant. linear on the ordinate scale. Note also 2. A decrease in potential tem- that on any given T line the vertical perature with elevation corresponds intervals between unit values di- to a superadiabatic lapse rate. minish upward, since varies as 3. The greater the rate of increase T/Pi'"^^, The convergence upward of in the potential temperature with ele- the dry adiabats follows from the re- vation, the greater the stability. lation that pi°""^* varies as Ti/^O, so It is essential that the reader be that as increases the slope TiXO de- thoroughly familiar with the concept creases along the 1000-mb line towards of potential temperature in order to

lower values of 0, appreciate the Rossby diagram. [Wet adiabats (= equivalent-poten- It should be mentioned here that, tial or wet-bulb temperature iso- strictly speaking, the potential tem- therms) are often added to the adiaba- perature as here defined is not the tic chart making it a pseudo-adiabatic quantity used as the ordinate in the diagram on which the behavior of sat- Rossby diagram, but a very nearly nu- urated particles can also be studied; merically-equivalent quantity known but this is of no concern to the present as the partial potential temperature discussion. Saturation specific humidity with respect to dry air. The total lines may also be added on the p°-^^^ pressure exerted by air is made up type of chart. These have the advan- of the pressure of the dry air (i.e., tage of being straight lines but are all the gases with the exception of curved on the log p diagram.] water vapor) plus the pressure If the pressure and temperature of exerted by the water vapor. The any particle of air be known, then partial potential temperature with one may find its potential tempera- respect to dry air is then defined as ture with the aid of the adiabatic the temperature the particle would chart by moving the original point have if it were reduced adiabatically

parallel to the dry ' adiabatic lines from the pressure exerted solely by until the 1000 mb line is intersected. the dry air to a pressure of 1000 mb. The temperature at this intersection The algebraic representation of this is the potential temperature. An quantity will serve to clarify the easier way is to label the slanting definition. If Oa represents the partial lines (the dry adiabats) with the par- potential temperature with respect to ticular potential temperature which dry air, p the total pressure of the remains constant along them. Thus air, T the temperature of the par- any point on the adiabatic chart which ticle, and e the partial pressure is determined by a pair of values of exerted by the water vapor, we have: and T has one potential tempera- p (1000 \ 0.288 ture, which may be ascertained from = T the dry adiabats. Potential tempera- p—e )

ture is practically always expressed This is, of course, similar in form to in degrees Absolute. the formula for the potential tem- With the help of the adiabatic perature, (p—e) replacing the p in ROSSBY DIAGRAM PLOTTING ROUTINE 15 the expression for potential tempera- sure for different temperatures may ture. But e is generally very small be found in most texts on meteorol- compared with p, and for this reason ogy or physics. Thus if one wishes ^d and do not differ appreciably. to find the vapor pressure at the tem- It is doubtful if, in practical meteor- perature of 10 °C and relative humid- ological work, it is worth while to ity of 50%, he finds in the saturation obtain Od rather than 0. However, vapor pressure tables the value of if numerical accuracy is desired, the 12.28 mb corresponding to 10° C. partial potential temperature may be Since the air is only 50% saturated, obtained by entering as the ordinate the vapor pressure is one-half of 12.28 of the point on the adiabatic chart, mb or 6.14 mb. Note that vapor not the actual pressure, but the total pressure is entirely independent of pressure minus the pressure due to pressure, being a function of tem- the vapor. This graphical process is perature and relative humidity alone. facilitated by locating the actual point After e has been determined, the of pressure on the adiabatic chart, specific humidity, q, is calculated by then displacing this point vertically means of the above formula. A slide upward by the number of millibars rule is most convenient for this com- of pressure exerted by the vapor. putation.

On one side of the adiabatic chart is It should be also noted that, strictly generally found a set of curves by speaking, the specific humidity is not means of which the specific humidity used as the abscissa of the Rossby be determined. conveni- may A more diagram, but rather a very nearly ent method of this computing quan- equivalent quantity called the mixing tity will be given below. The reader, ratio. This term is defined as the however, will find it helpful to dis- mass of water vapor per unit mass cover to use the specific how humidity of perfectly dry (absence of water curves on the adiabatic chart. vapor) air. In algebraic form: It has been pointed out that the

. . e specific humidity may be computed mixmg ratio (w) = 622 from the formula: p—e

From the above formula it is clear q = 622 that since e is very small compared P with p there will be no appreciable where q is the specific humidity ex- error introduced by the use of q in- pressed in grams per kilogram of air; stead of w. In fact, with the present e, vapor pressure, and p, the pressure inaccurate method of measuring the of the air. The units for e and p relative humidity in the upper atmos- may be chosen arbitrarily since they phere with the hair hygrograph, it is constitute a ratio. They are gener- ridiculous to try to obtain such an ally expressed in millibars, however, accuracy as the difference between since upper air observations are the formulae for q and w indicate. transmitted in these units. The value The use of the partial potential tem- of e, the vapor pressure, is readily perature and mixing ratio rather obtained by multiplying the relative than potential temperature and speci- humidity by the saturation vapor fic humidity as coordinates of the pressure at the temperature of the Rossby diagram, was made necessary particle. The saturation vapor pres- by the construction of the lines of 16 AIR MASS ANALYSIS

A 320 —

ROSSBY DIAGRAM PLOTTING ROUTINE 17

Use of The Rossby-Diagram as a The assumption is made at first that the air Nomogram for finding and q has just reached saturation. The point of intersection of Professor Rossby has also sug- the actual temperature line (under gested another method of obtaining the assumption this is also the tem- moist- the potential temperature and perature of the condensation point) ure content directly from the equiva- with the line for the given pressure lent-potential temperature diagram coincides with the point of intersec- which is presented at the rear of tion of the lines of actual potential Rossby's original paper.^ This par- temperature and saturation moisture ticular diagram differs from that content. Multiplying the latter by (see fig. in that described above 3) the relative humidity gives the exist- it contains, in addition to the 0, w, ing moisture content. Since the po- tempera- and Oe (equivalent-potential tential temperature in an adiabatic isobars isotherms ture) lines, the and expansion is constant until saturation the condensation level. With this for is reached, no correction is needed for particular diagram (and with one this quantity. operation in multiplication, which also The graphical method suggested by graphically) and may be done w Prof. Rossby is as follows: With the the may be readily evaluated from observed temperature expressed in values of p, T, and / obtained in an absolute degrees, enter the diagram airplane sounding. Dr. Byers' de- along the corresponding red tempera- scription of this method appears ture line until the observed pressure is undoubtedly a time sav- below. It line is intersected. Read the poten- find ing process, although one may tial temperature at the point of inter- in with a some difficulty working section from the black lines which run chart which has five sets of inter- horizontally across the diagram and secting lines. Anyone inexperienced the saturation moisture content from will find it with the Rossby diagram the black vertical lines. Multiply the better to practice first the basic latter value by the relative humidity. methods presented above until he has For this operation, a graph can be a good understanding of the funda- made consisting of saturation moist- mental quantities and operations. ure content and actual moisture con- J.N. tent as coordinates, with relative hu- [The Rossby diagram or equivalent- midity lines crossing diagonally.

potential temperature chart is avail- Example : Pressure 860 mb. Temp. able in a form which gives the pres- 3°C., or 276° A. Rel. Hum. 80%. sures and temperatures at the con- Follow red line of 276° to 860 mb, densation point of the air after an where potential temperature of 288.1 adiabatic expansion from the ob- and moisture content at saturation of served conditions of potential temper- 5.5 g/kg are indicated. Taking 80% ature and moisture content. A de- of this latter value, we find the actual termination in a reverse manner moisture content, which is 4.4 g/kg. makes it possible to evaluate the —H. R. Byersl. potential temperature and moisture Millar of the Canadian Meteoro- content from the ordinary observed logical Service has designed another pressure,' temperature and relative ^C.-G. Rossby, Thermodynamics applied to humidity data (See Plate I, in ref- air mass analysis, Mass. Inst, of Tech., Me- teorological Papers, vol. 1, no. 3. 41 pp., erence cited in footnote 2, p. 16). 1932. — —

18 AIR MASS ANALYSIS

out that this quantity is not conservative if nomogram for q and 0, which is shown any evaporation (of falling rain, or by subsi- in Fig-. 4.—B. G. S. dence) takes place, when it may lead to Note.—Beginning in the summer of 1938 the erroneous conclusions as to movement and U.S. Weather Bureau ceased regularly trans- identity of air masses. Rossby's equivalent- mitting over its telegraph and teletype circuits potential temperature is somewhat less con- the potential temperature (0) for each signi- servative for an evaporation process than the ficant level of the daily aerological soundings. adiabatic wet-bulb potential temperature. How- It became necessary therefore to compute all ever, there is no single index which is conserva- the derived values needed for plotting various tive for both adiabatic processes and evapora- energy and thermodynamic diagrams or 0^ tion, and since evaporation does not often lapse-rates, etc. However, the Bureau at the seriously invalidate the usual interpretation of same time published for its offices a new type the Rossby diagram the adiabatic wet-bulb and of adiabatic chart base {"Upper Air Map C") equivalent-potential temperatures are both which contains, besides the fundamental grid equally the best conservative elements available. of ordinary temperature vs pressure, only the Clark of California Institute of Technology slanting curves of the wet (saturation) adi- revised the Rossby-diagram by arranging the abats ; but on the margins are numbered 0B isotherms vertically and 0D lines hori- marks to indicate where the lines of potential zontally and plotting curved lines of constant temperature (straight), of saturation specific mixing ratio and isobars of the condensation humidity (also straight) and of kilometers level upon the chart. The characteristic of elevation above the sea, would intersect. curves will vary in slope through wider By using a ruler, or better still, a celluloid angles than on the original diagram, so that lines or glass transparent plate with sets of different stability conditions are more easily saturation for potential temperature and recognized at a glance (described in Taylor's specific-humidity drawn to scale on it, one can Aeronautical Meteorology, p. 60.). quickly evaluate these figures from the base Arakawa has published in Japan a new chart once the sounding is plotted thereon in form of the Rossby-diagram having for the ordinary terms of T, and q. Thus the p, ordinates the potential temperature on a new chart serves as a convenient nomogram. linear scale instead of partial potential tem- It supplants the temperatures vs height aero- perature on a logarithmic scale, and having logical plotting chart which has heretofore equivalent-potential temperature lines which been used for years in the Weather Bureau are calculated on the basis of convection in forecast offices and elsewhere. Owing to the saturated air with the heat of fusion taken small size of this chart it is not suitable for into account; also the diagram is extended to accurate work and will be supplanted by a over 20 g/kg mixing ratio so that it can be design. The large standard new and larger used for extremely humid tropical conditions. long been available Stiive adiabatic chart has The advantage of these coordinates is that the is but used chiefly at aerological stations ; it effect of mixing of two air masses can also too large for ready comparison of many be determined, since the potential tempera- soundings at once, as the forecaster must do ture of a mixture is equal to the mean of the in some countries. Editor. potential temperatures of the original air masses (Bull. Amer. Met. Soc, March 1940, Modified Rossby-Diagrams p. 111). Finally, the Refsdal "Aerogram" should be A number of variations have been proposed mentioned here since it combines the proper- and some are in use. They have some ad- ties of the adiabatic chart and the Rossby vantages in convenience but little if any diagram and the tephigram in one, though fundamental ones. Any diagram with two it is rather too complicated for the elemen- conservative elements among its coordinates tary student (see: Geofysiske Publik., Vol. XI,

Jan. p. 1 ; Bull. would essentially still be a Rossby diagram. No. 13 ; Meteorol. Zeit., 1935, For 0D Brunt (Phys. and Dyn. Met., 2nd ed., Amer. Met. Soc, Jan. 1940, p. 1). p. 92) has suggested substituting the (satu- (See also "A Note on Estimating Condi- rated) potential wet-bulb temperature and tional and Convective Instability from the Hewson has analyzed situations in that manner Wet-bulb Curve", at the end of Article VIII (see Bibliography). However, Bleeker points in this booklet.) ROSSBY DIAGRAM—INTERPRETATION 19

W' 20

1 1— 1 1 1 -i ~i 1 I r- 100 90 80 70 60 50 40 30 ZO 10

-40 -20 20 40 T I I 1 I I ' 1 400 1 ) \ ,- Tl I I 10 20 30 40 600 -5

240- 800 H -10 260- 1000 - 280- 15

300- _-20 320- W

340-

Fig. 4. The Millar Nomogram for Rapid Evaluation of w and 0, Showing Main Divisions Only.

Directions: To obtain w, lay a ruler across the p and r scales, setting the edge on the pressure p, and the percent relative humidity r. Then, holding the ruler rigid, hold a 90" set square against the ruler, and slide the square along until the edge is set at the temperature on the T scale. The corresponding value of w will then be read against the square on the w scale. To obtain 0, proceed in the same way, but setting on the p, w', and T' scales. For w', use the value of w previously obtained. (For further details see Bull. Amer. Met. Soc, Oct. 1935, p. 229; or June-July, 1936, p. 18). 20 AIR MASS ANALYSIS

IV. THE ROSSBY DIAGRAM—INTERPRETATION In the preceding article the me- a point. Owing to the fact that its chanics of plotting the Rossby dia- potential temperature must remain gram were discussed, and it may be constant, the point A cannot be dis- said here that the curve joining the placed from the horizontal line repre- individual points is called the char- senting its potential temperature. acteristic curve for the air column. Furthermore, the specific humidity The present article deals with the remains constant during the adiabatic significance of various curves on the process with unsaturated air, and thus diagram and the changes in appear- the point A cannot be displaced from ance of these curves as the more the vertical line representing constant common atmospheric processes, such specific humidity. It is evident, then, as vertical displacement, occur. At that the characteristic curve of a dry this point it is only fair to remind particle of air which is undergoing the reader that the following dis- adiabatic transformation reduces to cussion is, from the standpoint of a a point on the diagram. For a given quantitative analysis, rather unsatis- element of air this point will be rep- factory in that it is an attempt to resented by the same coordinates {6 describe processes which are better and q) until the level of condensa- expressed in more exact mathematical tion has been reached. From this terms. Yet it is hoped that tne level on it is assumed that the wat/er following will serve as an outline for produced by condensation drops out those who have a limited knowledge immediately—in other words, the of mathematics and physics. process is considered pseudoadiabatic In the Rossby diagram the char- {pseudo, since there is a small amount acteristic curve for an unsaturated of heat removed from the air by the particle of air, A (see fig. 5) having falling water). From the definition a given potential temperature {$) of equivalent-potential temperature and specific humidity (q) and being (^g) it is clear that the characteristic displaced vertically, is represented as curve of the saturated mass of rising

310 ROSSBY DIAGRAM INTERPRETATION 21

air is a line of constant equivalent- Soundings, then, made at different potential temperature. This amounts places within a source region and to saying that the lines of constant remaining within the same air mass

,$^ are also the saturation adiahats. should exhibit nearly identical char- In a rough fashion it is evident that acteristics; the characteristic curves the Oe lines must slope as they do; should be similar. Frequently the the potential temperature increasing air masses, even at the source regions in the saturated air particle because and particularly after travelling of the realized (latent) heat of con- some distance, are subjected to forces densation, and the specific humidity which lead to appreciable vertical dis- falling because of the condensation placements. When this occurs un- and removal of the liquid water. equally in different sections of the The fact that an adiabatic process air mass the homogeneity with re- with unsaturated air is represented spect to level tends to be destroyed. by a point makes the Rossby diagram The surfaces of constant potential particularly adaptable to modern temperature and constant specific •synoptic analysis. A thin layer of humidity become curved instead of air having a uniform distribution of horizontal, and plots of temperature temperature and moisture may be or moisture against elevation appear represented on the diagram as a markedly dissimilar. It follows that straight line. Let this line be CD it is difficult to identify and follow in fig. 5. If the entire layer CD be air masses by means of these dia- raised or lowered the temperature grams. The characteristic curves on and relative humidity of each particle the Rossby diagram, on the other of air within the layer will be hand, will have overlapping parts for changed because of the adiabatic ex- the same column of air regardless of pansion or compression. But the po- the extent of the expansion or com- tential temperature and specific hu- pression, providing no condensation, midity of each particle of air will evaporation, or introduction of a new remain unchanged, so long as conden- air mass has taken place. The reader sation or evaporation do not take may refer to papers published by the place, and for this reason the layer, Meteorology Course of the Massachu- compressed or expanded, will be rep- setts Institute of Technology and to resented on the diagram by the same Harvard Meteorological Studies, No. line CD. It is important to note 2, for examples of this characteristic that what has been said refers to one quality for various air masses on the stratum of air, no new strata being Rossby diagram. introduced or removed during the Fig. 5 illustrates characteristic process. The line element CD may winter curves for two air masses: then be considered as the charac- one having its source over Northern teristic curve for the given layer. Canada (Pc—Polar Canadian) the If an entire aerological sounding is other from the Gulf of Mexico (Tg plotted on the Rossby diagram, it —Tropical Gulf).* The numbers, be- may be considered as the charac- side points on the curve, repreg?nt teristic curve of the air column elevations in kilometers above sea through which the sounding has been level. The Pc curve exhibits the pro- made. nounced coldness, dryness, and stab-

In the definition of an air mass, *For description of these air masses see the article by Prof. Willett in the back of this liorizontal homogeneity was stressed. booklet. 22 AIR MASS ANALYSIS

ility of the Polar Canadian air. The the Rossby diagram. From the slope Tg curve shows the warm and moist of the characteristic curve relative character of the tropical maritime air. to the slope of the lines of constant The Rossby diagram is helpful in Op, one can determine whether the the treatment of stability. Thermo- layer in question is convectively un- dynamic diagrams, for the most part, stable (sometimes called potentially deal with the stability or instability unstable). This condition is defined of a particle of air with respect to as one in which the equivalent-poten- its surroundings. This is of import- tial temperature decreases with ele- ance in penetrative convection^ such vation, and is indicated on the Rossby as in cumulus cloud and thunderstorm diagram by a line which possesses a formation. However, in the more im- slope between those of the lines of portant types of convection, that is, constant 0-^ and constant 0' In other in the case when a layer of warm words the line representing convective air of large horizontal extent is instability is one which lies between forced over an underlying cold air the potential and the equivalent-po- wedge or a mountain range, the tential isotherms. The importance of classical energy diagrams fail to give this particular distribution of tem- a measure of the potential energy perature and moisture lies in the fact available in the layer. It is here that that lifting of the entire layer brings the Rossby diagram is invaluable. about a more unstable condition, in It is true, however, that in regard to fact, if the layer is lifted sufficiently particle stability the classical dia- it will eventually become unstable grams are more useful than the with respect to dry (unsaturated) Rossby diagram, but even in this air. The following illustration will type of stability it is not difficult to serve to show this increasing in- apply the equivalent-potential tem- stability. Suppose we have the layer perature diagram of Rossby. This CD, which is by definition convectively may be done with the aid of the lines unstable, having the equivalent-poten- of equal potential temperature (the tial temperature 320° A at the base horizontal lines) and the elevations of the layer and 315° A at the top. of the points which may be conveni- If the layer is now lifted pseudo- ently indicated by figures beside the adiabatically to the top of the atmos- individual points of the sounding. phere, the base of the layer will have Thus if there is no increase in po- an equivalent-potential temperature tential temperature through a layer, greater than that at the top of the the lapse rate is equal to the dry layer by 5 C deg., the additional heat adiabat, or 1 C deg. per 100 m. If being supplied to the bottom of the there is an increase in potential tem- layer by the extra heat of condensa- perature of 10 deg. in 1000 m the tion given to it by the greater amount lapse rate is isothermal. In general, of water vapor at the base compared the greater the increase in poten- with the top of the layer. This de- tial temperature with elevation the crease of potential temperature, of greater the stability. If the potential course, denotes instability with re- temperature decreases with elevation, spect to dry air. If the temperatures the lapse rate is superadiabatic. base of the layer were The second type of stability, that at the top and intervals in the within a layer which is being dis- taken at successive placed vertically, is best treated by ascent of the stratum the difference THE WARM FRONT 2a in temperature would be seen to be- or layers of convective instability come greater and greater. Thus any within an atmospheric sounding does layer of air which was originally not mean that the energy stored convectively unstable, when subjected therein will be released in the form to lifting, will acquire a steeper lapse of convection. The meteorologist must rate, eventually reaching a state of consider whether vertical forces instability with respect to dry air. brought about by thermal or mechan- Inspection of fig. 5 will reveal that ical convection will come into play a decrease in Oe "with elevation may sufficient to lift the layer enough to be brought about in different ways. convert the potential energy of the For example, it may be due to a layer into kinetic energy. In this rapid drop in temperature vnth ele- connection reference must be made vation (that is, a small change in po- to the synoptic chart. tential temperature), a rapid decrease If the equivalent-potential tem- in the moisture content with elevation, perature increases with elevation the or of course a combination of both. state is one of stability with respect Reference to the relative humidity to dry or saturated air^ and no adia- distribution and lapse rate is suffi- batic process performed upon the cient to indicate to the synoptic layer can render it unstable. meteorologist whether the convective Another important use of the instability is due to the moisture or Rossby diagram is in distinguishing to the temperature distribution. In between temperature inversions this connection it is well to note that which have developed within the same convective instability may or may not air mass and those which are the carry with it conditional instability. result of a warm current overrunning Similarly, conditional instability is a cold wedge. In the latter case the not necessarily accompanied by con- warm current generally has, level for vective instability. level, a much higher moisture content The idea of convective instability than the cold current. For example, may perhaps be made clearer by deal- let us suppose that we are dealing ing with a special case in which the with a wedge of cold air which had base of a stratum is nearly satu- its source over northern Canada rated, while the top is very dry. Lift- while a current of warm moist air ing of this layer will lead to satura- from the Gulf of Mexico is overrun- tion of the base long before the upper ning it. A sounding made through layer. Thus the lower part of the the cold wedge of air into the warm layer cools at the rate for saturated current would then show a rapid air at those temperatures, while the increase of moisture and potential upper part of the layer cools at the temperature. The rapid increase is adiabatic rate for dry air. It is shown in the Rossby diagram (curve obvious that the base of the layer is EF, fig. 5) where the wedge-like becoming warmer and warmer rela- curve shows a maximum specific hu- tive to the top of the layer, thereby midity aloft. In one and the same increasing the lapse rate. Further- air mass the specific humidity gen- more, even after the entire layer erally falls off gradually. This would becomes saturated, the base of the be expected in view of the fact that layer is receiving more heat of con- all atmospheric water vapor origin- densation than the top of the layer. ates at the earth's surface. On the The mere existence of some layer other hand, soundings obtained —

24 AIR MASS ANALYSIS

within one and the same current of advantage can be readily demonstrated. All synoptic meteorologists air show no pronounced wedg^e-like agree, however, that some such diagram as Rossby's should be a curve, but instead a continued de- familiar tool and that it is invaluable for crease in the moisture content. teaching principles to students and for re- The method of making use of the search. The diagram still finds much use as a nomogram for finding etc., and Rossby diagram in practical meteor- 0, 0^, other thermodynamic computations. For identifying ological work is best grasped by convective instability it is only necessary to

studying synoptic discussions in have a table of the /Qj, lapse rates for the which the diagrams are used, and if sounding. In the note on wet-bulb temperature appended to Article VIII is indicated possible, making daily use of them how all types of stability and energy distribu- in conjunction with the analyzed tion can be recognized on the tephigram or weather maps.* emagram alone, thus obviating the necessity Note on present use o/ the Rossby and other of plotting two or three charts. Even the diagrams.—The Rossby diagram is no longer Stuve pseudo-adiabatic chart, which is usu- so extensively used in daily routine weather ally plotted anyway in all weather services, analysis in the United States as some years can be adapted in a crude way for all the ago. (The use of tephigrams and emagrams purposes attributed to other charts and since

likewise seems to have decreased ) . The reason time is at a premium there is a tendency for for this appears to be in part the lack of American forecasters to depend on it almost time available for plotting additional charts, exclusively. In a tropical country the tephi- but more importantly the increasing experi- gram is probably the most convenient all- ence of the analysts which permits them to purpose chart (see Article VIII). The Refsdal recognize the air masses and stability condi- "Aerogram" is designed to combine features tions from an inspection of the surface map of all other diagrams and is being used in and of the aerological soundings plotted on some services. Its inconveniently small scale adiabatic charts or against height. Time and the complications of many overlapping available to forecasters is so limited that the coordinate grid-lines do not commend it for introduction of additional charts is resisted students, nor for speed and simplicity. by them except where some very indispensable R. G. S.

V. ELEMENTS OF FRONTAL STRUCTURE—THE WARM FRONT Anyone who has worked with a separation between the two currents. close network of surface observations The methods of air mass and frontal clearly recognizes the existence of analysis are primarily based upon the zones in which the rate of change of postulate that the zone of separation the commonly observed meteorolo- between currents of air possessing gical elements, e.g., temperature, is different properties may be treated comparatively large. These zones of as a surface of discontinuity. Atmos- rapid transition of the elements are pheric discontinuities, to be sure, are the "fronts" of the Norwegian system not absolute mathematically abrupt of weather analysis. In the general transitions, but rather are zones in treatment of air masses it was pointed which the change in the elements is out that large-scale air currents, far more rapid than within the air in spite of a long trajectory, tend masses on either side of the front. to retain their original properties, These discontinuities are not purely this being particularly true at upper surface phenomena; they are sur- levels. It follows, then, that as two faces which generally slope back- air masses, one from polar regions ward (or forward) over the cold air. and the other from tropical regions, If an ideal case is assumed in which converge, there must be a zone of a warm current of air flows side by

*See synoptic papers by Willett, Emmons, side but in opposite direction to a Namias, and Byers, 1932-1936, in Bibliography. —Ed. cold current the following formula THE WARM FRONT 25 gives the slope of the surface of undergoing some modification; per- separation between the two currents: haps they are becoming steeper, perhaps accelerating, or perhaps undergoing various transformations simultaneously. The reasons for these where tan is the slope of the front, fS deviations from ideal stationary con- I the deflective force due to the ditions are beyond the scope of this earth's rotation, g the acceleration of series of articles. It can be seen, gravity, Ti and T2 the temperatures however, that if a wedge of cold air of the two currents, and Vi and V2 is too steep, that is, if it exceeds the corresponding velocities. From the equilibrium value of slope given this formula we see that, other fac- by (1), it will tend to flatten out, tors remaining the same, the slope the colder air spreading out under- of this ideal stationary front becomes neath the warmer. This leads to greater as the difference in tempera- vertically upward components in the ture between the two air masses (in- warm air ahead of the front which, volving T2—Ti in the denominator) in turn, may lead to adiabatic cool- becomes smaller. Also, an increasing suflficient to form cloud. Like- ing difference in the velocities on wise, a slope which is not steep either side of the front, other things enough will become steeper. In this being the same, requires an increas- case a downward component is estab- ing slope. lished within the overlying warm air. In the development of the above Once the stationary equilibrium of a expression, several assumptions are front is disturbed so that, e.g., there made which, though probably never is convergence of wind flow, the warm rigorously attained in Nature, are air is forced to ride over the under- frequently approximated, e.g., the air lying cold wedge. Then most of the flow on both sides of the front is upward component is more likely a assumed to possess no curvature. result of this convergent flow rather Slow moving fronts often approach than of any change in slope of the this linear character. front. The conditions necessary for equilibrium of two air currents which are Perhaps the most convenient clas- flowing side by side are, then, that sification of discontinuity surfaces is the cold air must underlie the warm one based upon the active or passive air in the form of a wedge and must nature of the vertical component in flow, in the northern hemisphere, to the warm air above the cold wedge. the right of an observer looking from In the active case the vertical com- the colder into the warmer air mass. ponent is a result of processes which If, in the atmosphere, these sur- are independent of the cold air; in faces of discontinuity remained sta- the passive case, the moving cold air tionary under the conditions of equi- brings about forced vertical move- librium outlined above, there would ments in the overlying warm air. be little or no change in the weather, In this article we shall deal solely for weather changes are primarily with the class of discontinuities in the result of frontal movements aiid which the warm air possesses an up- air mass interactions. Complete equi- ward component of motion due to librium within the earth's atmosphere convergence into and ascent over an is never reached. In other words, underlying cold wedge of air. These frontal surfaces are continually discontinuities are termed warm 26 AIR MASS ANALYSIS

^^^^^«i7a;-27*w«- /i/g'/? //7P'€'rs/o/?

Ji/rface

Fig. 6. Idealized Vertical Cross-Section of a Warm Front (After Bjerknes). (Reproduced from fig. 90. Bull. Nat. Res. Council, No. 79.) fronts. Cold fronts, aggressive earth's surface features over which wedges of cold air which force warm the front is traveling, and the vertical air upward, will be taken up in the structure of the warm and cold air. next article. Discontinuities charac- The effect of surface friction in a terized by a downward component of retreating cold wedge (a warm warm air flow along a surface of cold front) tends to flatten the wedge in air are given the name surfaces of its lower sections. Thus, for some subsidence. They also will be treated distance ahead of the warm front it later. is sometimes observed that the slope In the case of a warm front the is almost horizontal. When this is cold air acts as a barrier to the true, a point well ahead of the front warm flow, the resulting vertical dis- will generally be found at which the placement leading to the formation slope of the discontinuity increases of clouds and perhaps precipitation. comparatively rapidly. On the syn- Figure 6 shows the characteristic cir- optic surface chart such a distribu- culation, cloud forms, and precipitation may appear as another front, tion area generally associated with particularly in the precipitation field, a well-defined warm front. In the for the steep slope causes consider- eastern part of the United States the able ascent of the warm air. over-running warm air is most likely The vertical structure of the warm to have come from the Gulf of Mex- air with respect to temperature and ico or the tropical portion of the moisture distribution is important for Atlantic Ocean, while the underlying types of cloud and precipitation. For cold air is most frequently an air example, if the warm current be mass of Polar Canadian origin. This stable and dry, as is frequently the combination of air masses represents case with currents of Tropical Pacific extremes of warmth and moisture air, after crossing the Rocky moun- on the one hand and of coldness and tains, condensation forms may be dryness on the other. The interac- entirely lacking, and considerable tions of these two currents are re- ascent of the warm air will be neces- sponsible for most of the winter sary to produce condensation. On precipitation of the eastern part of the other hand, if the warm current the country. is conditionally unstable, the ascent Actually there are many modifica- over the cold wedge may become tions which are introduced into the vigorous enough to form thunder- ideal scheme shown in Figure 6. storms. If the current be convec- Modifications may be induced by the tively unstable the lifting of layers, —

THE WARM FRONT 27

if carried far enough, will eventually evaporating rain and secondly, in the lead to voluntary convection of the cold air adjacent to the surface of warm air, and hence shower type discontinuity, the lapse rate tends to precipitation. In our Tropical Gulf steepen. air masses this is normally the case. In the lowest layers of the cold One does not always find a continuous air, perhaps 100 m. above the surface cloud layer above the warm front of the earth, Frst clouds (scud) may surface as indicated in figure 5. be formed by turbulence in this Rather, one often finds two or more almost saturated lowest layer of air. layers of clouds separated by com- The identification of warm fronts paratively clear spaces. This does on the surface weather map is fre- not invalidate the frontal idea, but quently very difficult. The wind dis- merely indicates that the air is continuity may not be pronounced ascending the front in layers. Since and to complicate matters further tne the warm current is generally ob- transition of temperature may often served to be stratified in its tempera- appear relatively gradual. This dif- ture and moisture distribution, it is fuse distribution of surface elements probable that, as the successive across a warm front is explained by layers ascend, condensation appears the small angle of slope of the dis- at some levels sooner than at others. continuity surface. At high levels The cloud layer, in the event of the it is probable that there is little mix- release of marked instability, is apt ing of the warm and cold air, but in to be thick. the turbulent layer lying within about The structure and trajectory of 600 m of the surface, if the dis- the underlying cold air current, continuity surface is not far from while not particularly important for the ground, there must be some con- the production of precipitation, is siderable intermingling of the warm nevertheless significant for the types air with the lower cold air. Thus, of clouds which are observed. Where the temperature and moisture con- the cold current has passed over a tent of the air some distance ahead water surface, there will generally be of the warm front gradually increase. found a layer of Stcu cloud, which A good rule to remember in this con- obscures from view the upper layer nection is that the gradual changes of clouds associated with the warm which occur in the transition zone are front. The elevation of these lower entirely within the cold air. Thus in clouds is rarely over 500 m, their the warm air current the meteoro- thickness seldom appreciable, and the logical elements, particularly temperature and precipitation from them, if any, is moisture, should remain comparatively constant. only mist, or at most, drizzle. Occa- air sionally, at intermediate levels within Upper soundings offer the best aid to the identification of the cold air, there is found a layer warm fronts. As pointed out in Article of Acu clouds. These seem to be IV associated with surfaces of subsid- of this series, a sounding through a ence, to be discussed in a later article. warm front appears on the Rossby In the cold air through which rain diagram as a wedge-shaped curve is falling, conditions are becoming with a maximum water vapor con- increasingly favorable for the forma- tent in mid-air (fig. 5, in Article IV). tion of clouds, for, in the first place, The base of the warm current is gen- the moisture content is increased by erally considered as the point of the —

28 AIR MASS ANALYSIS

wedge on the Rossby diagram. If one another. This not only helps in other soundings have been obtained identification, but indicates the modi- within the warm air their character- fication which has been taking place istic curves should be compared v.'ith within the air current. VI. ELEMENTS OF FRONTAL STRUCTURE—THE COLD FRONT Cold fronts belong to the class .cf outlined in Article V of this series. discontinuities in which the warm air This is equivalent to saying that in lying above the cold wedge is forced order for vertical motions to arise to rise, the energy being supplied there must be a zone of convergence. mainly by the moving wedge of cold The convergence may be interpreted air. The most pronounced cold fronts as the attempt of the adjacent air are easily recognizable on the surface masses to bring about an equilibrium weather map as marked wind discon- of frontal slope. tinuities, the well known wind-shift The typical cold front* is usually lines. On the other hand, there are portrayed in vertical cross-section as many cold fronts not characterized is shown in Fig. 7. In this diagram by abrupt changes, and thus not so the vertical scale is of course greatly easily identified. The slope of the exaggerated with respect to the hori- cold front surfaces of discontinuity zontal. The wedge assumes the form is characteristically greater than that of a squall head in its foremost sec- of the warm fronts, the values being tion owing to the fact that the cold of the order of about 1/50 in the case air is retarded by friction at the of the cold front compared with per- surface of the earth, while at some haps 1/200 for the warm front. distance aloft, where frictional effects These are merely rough averages; are small, the cold air runs ahead. in any individual case the slope may The elevation of this foremost part be appreciably different. *According to Bergeron the cold front is of

two main types : The first kind of cold front The importance of fronts in is an "anafront" in which there is general upsliding motion of the warm air along the weather analysis lies in the fact that front surface and formation of a rather broad they lead to the formation of vertical post-frontal Ast-Nbst system—this type will only occur with a retarded or slowly moving atmospheric motions, which in turn front. In the "kataf ront", the second kind of bring about regions of cloudiness and cold front, the warmer air ascends only in the lower layers, the warm air above 1-4 km gener- precipitation. It must be borne in ally moving forwards faster than the cold wedge, mind, however, that no vertical mo- sinking and thus turning the cloud system into a mainly prefrontal one of Acu-char-

tion will be present at a front which acter ; this kind of cold front is by far the commonest type. Bull. Anier. Met. Soc, Sept., obeys the conditions of equilibrium 1937, p. 266.)—Ed.

Fig. 7. Idealized Scheme of a Cold Front (After Bjerknes). (Reproduced from Fig. 91, Bull. 79, Nat. Research Council) THE COLD FRONT 29

of the cold tongue is generally about importance to the forecaster. 500 meters above the surface. The The ceilings in advance of a well- form of the advanced portion of the defined cold front decrease compar- cold wedge depends upon the rough- atively rapidly. The foremost por- ness of the surface over which the tion of the frontal cloud deck in the front is traveling, the surface cold warm air may be a Ci or Cist type air being the more retarded the which rapidly lowers to Acu and A^st, rougher the terrain. In hilly or moun- and finally to Nbst. This transition tainous sections changes from the may take place in a period of two warm to the cold air are frequently hours. At times rain may be seen less abrupt than over flat country. As falling from the clouds and evapor- the cold air tongue moves in at some ating before it reaches the earth. upper level there is certain to be The frequently observed temperature some mixing with the underlying fall in advance of the cold front warmer air. The existence of a coJd is sometimes associated with evapor- current aloft implies a steep lapse ation of rain from the clouds, the rate, which facilitates convective stir- cooling extending down to the surf?.ce ring, and even possibly, for a brief through turbulent mixing. When this interval of time, a superadiab-itic is the case the specific humidity at lapse rate. It also seems logical that the surface increases as the tempera- the cold air aloft may at times break ture falls. This phenomenon im- off from the main body, much the mediately precedes the rain. same as the crest of a water wave. There are times when the precipita- It is difficult to determine how far tion is entirely confined to the region the cold air may run ahead of the ahead of the front. Here the struc- surface boundary of the front. Per- ture of the warm air is usually of a haps twenty-five miles is an average, conditionally unstable character at one hundred miles a maximum value. intermediate levels (say, 1000 to 3000 The rain which occurs before the m), and the initial upward impulse arrival of the cold air at the surface some distance ahead of the surface (prefrontal rain) is mainly the result cold front is sufficient to release and of vertical lifting of the warm eir transform the potential energy into by the mechanical action of the ad- convective showers. Behind the cold vancing wedge. The cloudiness and front the vertical forces may be in- character of the precipitation depend sufficient, or the structure of ^he upon the vertical structure of the warm air at higher elevations un- warm air which is being displaced. favorable for precipitation.

If the warm current is fairly dry and In other cases the rain zona is stable, e.g., a current of old Polar concentrated behind the front, i.e., Pacific air. the cold front may arrive within the cold air. In this case the accompanied only by a broken cloud component of wind flow normal to deck and no precipitation. On the the front is appreciably greater in other hand, if the warm air is Tropical the cold air than that in the warm Gulf air, moisture-laden and condi- air. Sometimes a cold front becomes tionally unstable, the clouds are apt almost stationary; precipitation and to be of the Cunb type with the char- cloudiness begin to spread far behind acteristic frontal thunderstorms. It it. Pilot balloon observations well is evident, then, that an upper air behind the front then show the warm sounding within the warm air is of current flowing in opposite direction 30 AIR MASS ANALYSIS

to the cold air. The cold front soon principles can be given which may retrogrades, and thus, by definition, be of value. becomes a warm front. As a cold front moves into more Normally, clearing takes place southerly latitudes its slope decreases rapidly behind the cold front. The in accordance with formula (1) in continuous cloud deck associated v/ith Article V. Thus, in the southern the front passage soon appears to section of the country, it is common break up into Cu or Stcu clouds. to find the warm air not far above Actually, however, these lower clouds the surface, even though the position are not a result of the discontinuity of the surface boundary of the air surface, but rather are associated masses is distant. The cloud deck with the cold air mass which is dis- accompanying such a front is in gen- placing the warm. The formation of eral horizontally extensive. Like- these clouds is somewhat as follows. wise, its base has a very small angle The cold air mass has come from a of inclination. In fact, in the south- cold source region; therefore, it is ern section of the country the cloud colder than the surface over which deck associated with a slow-moving it is traveling. Since the lower front of polar air frequently touches layers are continually being heated the ground, producing widespread the lapse rate becomes steeper until fog. An airplane sounding shows a the dry adiabat is reached. The lower very thin layer of cold air, above particles of air then rise and cool. which there is a large temperature This process, carried far enough, inversion, the warm and moist Gulf leads to the formation of the Cu air being aloft. The extensive fog or Stcu clouds, and if vigorous, re- is probably in large part due to satu- sults in showers or snow flurries ration by falling rain or the mixing (instability showers). Soon after the of the saturated, or nearly saturated front passage one may observe, Gulf air, with the cold Polar air com- through the breaks in the lower posing the thin wedge. Precipitation clouds, the layer of continuous cloud falling from the warm Gulf air is, which lies along the discontinuity in the South, almost always in the surface of the cold front. The ele- form of rain. The cold air below vation of the base of the Stcu or Cu the inversion, however, may possess clouds formed within the cold air temperatures well below freezing. In remains fairly constant, but their this event the rain is subcooled in its height is somewhat less nearer the fall through the cold air, and readily front. This is explained by the sact freezes on striking objects. Thtn that the cold air near the front is again it may freeze in mid-air and more moist than the air farther back, fall as sleet. owing to the precipitation which has If the cold air passes over a fallen through the cold air and to warmer water surface, e.g., the Great the evaporation from the moist Lakes, the rapid warming and addi- ground. tion of moisture generally leads to In traveling over different regions the formation of snow flurries. Con- there are many modifications which ditions are most favorable for those the cold front undergoes. While there instability flurries when the contrast is no substitute for practical experi- between the temperature of the water ence in interpreting the phenomena and the Polar air is most pronounced, in any locality, a few more general i.e., in late fall and early winter. CYCLONIC STRUCTURE 31

The flurries begin shortly after the to form snow flurries. At night the cold air arrives and continue as long snow flurries either disappear or dim- as the temperature difference obtains, inish in intensity. and the upper wind flow carries the To the lee of a mountain range clouds over the particular location. the air is forced to descend, which It is sometimes observed that snow opposes the formation of lower flurries of this sort occur when the clouds. In these regions, therefoie, wind at the surface is blowing off the rapid clearing takes place after a land. In this case observations reveal cold-front passage. The temperataie, the wind at levels slightly above the OAving to the foehn effect, is also surface, say 500 to 1000 m, coming higher than that normally prevailing from a direction off the water. Evi- at the same level in the cold air dently convection has taken place in mass. the off-land air, which is colder than Sometimes a cold front may de- surface, the water and the resultant generate into two discontinuities. In clouds and flurries are carried back this case each discontinuity acts as a over the land by the upper component distinct front, the passage being ac- of the circulation. companied by fairly definite changes In mountainous country orographic in the meteorological elements. These effects upon the cold air often lead secondary fronts are developed when to cloudiness and precipitation. There the cold front is accelerating, for it are several factors which enter into can be shown that the velocity field the problem; only a brief outline can of air flow is such that there must be be given here. Forced vertical con- a descending current of air some dis- vection, brought about by the rough- tance behind the main front. The ness of the surface features, pro- descending air leads to the formation duces clouds, if the lifting is sufli- of a new discontinuity between the cient. But the vertical temperature sinking cold air adiabatically warmed, and moisture distribution in the cold and the fresh polar air which is not air may oppose the ascent of Ihe descending. The transition zone of air. That is to say, the cold current descending air frequently appears in may be dry and stable; the air upper air soundings as a dry and will then tend to flow around obstruc- stable layer. tions rather than over them. Since While cold fronts and warm fronts vertical motion depends on the lapse have been treated independently thus rate it is logical to suppose there far, they must not be considered should be a diurnal variation in the as separate and disconnected phe- cloudiness resulting from the abo\e nomena. Both are necessary parts of cause. During the day time, when the irregular circulation of the mid- the lowest layers are warmest, the latitudes. Both are complementary lapse rate is steepest; on this ac- parts of the cyclone, the structure count less force is required to produce of which will be treated in the next the vertical displacement necessary article. VII. ELEMENTS OF CYCLONIC STRUCTURE In the preceding two articles of pointed out that both are comp?e- this series warm and cold fronts w.-re mentary parts of the cyclone of the discussed as independent entities. At surface weather map. The problem the close of the last article it was of the formation and maintenance —

32 AIR MASS ANALYSIS of these disturbances, which are called then, using this as a foundation, to extratropical cyclones, is exceedingly extrapolate conditions and, what is complicated and is as yet unsolved. of more importance, estimate the mo- To account for these depressions of difications which may occur. The the mid-latitudes the Norwegian method of fronts and air masses school of meteorologists, under the is particularly well adapted to both leadership of Professors V. and J. extrapolation and determination of Bjerknes, have formulated what is modification. It thereby supplies a now generally known as the Polar more quantitative basis for prognos- Front Theory. Since the inception of tication. this theory (during the World War) The convergence of two air masses secondary modifications have been of different properties leads to a sur- added by the Norwegians themselves face of discontinuity. There are, on and by meteorologists of other coun- the earth's surface, regions where tries. In fact, at present data are large-scale air currents of appreciably being collected and studied which, different properties generally con- within the next few years, may lead verge. Bergeron has called these to extremely important modifications regions of frontogenesis. Regions of of the fundamental ideas underlying divergence, where fronts are not the Polar Front Theory.* readily formed, and where they are In the following article Dr. Haur- generally destroyed, are called re- witz, an authority on the mathe- gions of frontolysis. For example, the matical part of the Theory, interprets region south of the Aleutian Islands it for the general reader. But quite may be considered as a breeding apart from their validity for a theory ground of fronts, because the Aleu- of the origin of cyclones (still not tian Low, a vast center of action widely accepted), the basic concep- formed and maintained chiefly by tions of the Norwegian school have thermal differences between the rela- been looked upon as extremely valu- tively warm waters of the North able tools in the analysis of weather Pacific and the cold snow-covered conditions. No impartial observer can areas of Alaska and Siberia, serves doubt that the use of frontal ideas to draw cold Polar Continental air as a method of interpretation of me- into its western side and warm trop- teorological phenomena has served to ical air to its eastern side. The objectify and clarify for the synoptic juxtaposition of these two air masses meteorologist the description of at- results in the Polar Front. mospheric movements. Weather fore- If the front formed in the AleU'.ian casting should be considered as an region always remained stationary attempt to give first a physical inter- under the equilibrium outlined in pretation to what has taken place, Article V, it would have no dynamic significance. That is to say, it would *Prof. Rossby has recently seriously ques- tioMed the Polar Front Theory in so far as it simply represent the boundary zone concerns the general circulation of the at- between the cold polar and the warm mosphere, the flow patterns in the upper air, and the significance of fronts and air masses. tropical air, and, since there is a That many cyclones do form from waves on a Polar Front in the lower portion of the tro- balance of forces, there could be no posphere is not denied, however. See : Bull. vertical motions—hence no precipi- Am. Met. Soc. 1937, pp. 201-209 ; Trans. Am. Oeophys. Un., 1937, Pt. I. pp. 130-136; tation. It may be shown, however, and On the Role of Isentropic Mixing in the General Circulation of the Atmosphere, that this equilibrium cannot exist, Trans. 5th. Int. Ccmgr. of Applied Mechanics, for there be an exchange of Cambridge, Mass., 193S, pp. 373-8. Ed. must THE COLD FRONT 33

A-St.or

VtS'^'^^ Co/a' /7/r -, —> •:i:i:i

(9) r/i;

Fig. 8. Formation and Occlusion of a Cyclone.

air from the polar to the tropical moves off with the system to the regions to compensate for the pole- southeast, becoming a migratory ward flow which must be preseni in cyclone of the mid-latitudes. the upper levels of the atmosphere. The Polar Front, which has now This conclusion is based upon observ- been pushed to the south, may extend ations which, in the mean, show a in a general NE-SW direction, and definite poleward pressure gradient usually slows up in its more south- aloft. Furthermore, it can be shoivn erly portion. We now have a sV.w that the interchange of polar and moving discontinuity between tne tropical air must take place sporadic- polar and the tropical air. This ally and irregularly, the polar air front, because it marks the boundary breaking out in vast tongues and dis- surface between two currents of dif- placing the warmer air in its path. ferent density and is almost station- When this occurs the original low, or ary, is particularly favorable to the the primary cyclone as it is called, formation of wave disturbances on 34 AIR MASS ANALYSIS the front—bulges in the line of the of the translational velocity of the discontinuity. The origin of thr~se wave itself (i.e., the velocity it would waves is to be sought in the factors have in the event the mean resultant which, acting together, determine the velocity were zero). In this connec- equilibrium of the frontal surface. tion it is well to note that the com- An upset of this equilibrium at some ponent of translation due to the wave section of the front may readily motion in the medium obeys the gen- develop into a wave.* eral physical laws of wave motion, In Fig. 8 (a) the Polar Front is i.e., flat, long waves travel rapidly shown before the beginning of a wave compared to waves of large amjili- disturbance. Arrows represent the tude. It may also be shown that, in air flow; (b) shows the formation of the northern hemisphere, the com- a bulge in the front which is the ponent of velocity due to the wave start of a wave. The stippled area motion itself must be so directed that indicates where precipitation is fall- the wave moves to the right of an ing. In this case it is the result of observer looking from the warm into the vertical displacement of the trop- the cold air. If the mean velocity of ical air over the cold underlying the interacting air currents also pos- wedge. In the final analysis this is sesses this direction, it is clear that due to the disturbance of equili- the wave will travel rapidly. On the brium. There are now two possi- other hand, if the resultant velocity bilities: the wave may travel along of the air currents is directed op- the front and remain a wave disturb- posite to the component due to the ance, later flattening out and dying; wave motion, the wave will move or, as it moves, it may increase in slowly, or it may even be fairly 'Sta- amplitude to such an extent that one tionary. In the United States the side of it overtakes the other. This wave component of the velocity is of question of the stability of the wave more importance, for here the fronts cannot be treated in any detail here. frequently have a NE-SW direction Most of the disturbances which re- and the cold NE current generally main as waves along a front are those falls off rapidly with elevation. In of small amplitude and short length. the United States, then, the normal Longer waves of relatively large am- movement of wave disturbances is in plitude tend to close up—the cold a general easterly or northeasterly air completely displacing the warm direction. (See Fig. 12.) air from the surface. If the wave continually increases The movement of these waves, ac- in amplitude its successive stages are cording to V. Bjerknes, is the vector represented in fig. 8 by (c), (d), (e), resultant of two components (Fig. 12) : and (f). In these diagrams the solid (1) the dynamic component of the vel- heavy lines represent cold fronts; the ocity due to the displacement of the double light lines, warm fronts; ^he wave motion along the boundary sur- broken heavy lines, occluded fronts face and the movement of the (2) (defined below) ; and the light solid medium itself (the air in the vicinity lines, isobars. Stippled areas sbow of the front). Thus the -forecasting where precipitation is falling. The of the motion of these waves is ba&ed right-hand section of the wave be- upon an estimate of the mean resultant velocity of the air currents in *The theory of this is explained in the the frontal region and an estimate article by Haurwitz following this chapter. .

CYCLONIC STRUCTURE 35

comes a warm front, for here the front is colder than the air behind warm tropical air is forced to over- the cold front, the occlusion will as- ride the cold wedge of air underlying sume the form of another warm front it. The left-hand portion of the wa\e in the lower layers. This latter case then becomes the cold front of the is illustrated in (h) which may be system—a wedge of cold air which is considered as a vertical cross-section displacing the warm air. In normal through the line AB of (f). The in- cases the field of flow is such that tersection of the sloping front with the cold front travels faster so that the earth, in Fig. 8 (h), is drawn on it soon begins to overtake the warm the weather map as the "occluded front, as is illustrated at the point front;" also, the position of the inter- in (e). When this occurs the pro- section of the cold and warm fronts cess of "occlusion" is said to be aloft is projected on the weather map taking place. Stage (d) represents and drawn as a dashed line (in the start of the occlusion. As the U. S. A.) known as an "upper (cold) cold front meets the warm front the front" (see Bergeron's model, p. 122-4) warm air lying between them is com- The type of weather associated with pletely cut off from the surface of an occluded front passage will, then, the earth and exists only as an en- depend largely upon the vertical struc- trapped body of air at upper levels. ture. If the temperatures of the two Hence it is "occluded" (closed off) adjacent cold currents are fairly from the surface. The front between alike, the entrapped warm air will the two cold air masses is called an determine the effects observed; if the occluded front. On surface charts it warm air is still being lifted appre- is represented as a line, e.g., the ciably precipitation may be abundant. heavy broken line in (e) and (f). It is clear that the temperature and Owing to the fact that the air moisture distribution within the en- currents on both sides of the cyclone trapped warm air is also to be con- have had different trajectories, the sidered in forecasting what is to temperatures, and thus densities, of happen. The general laws of stab- the two cold currents are not the ility are applicable. It frequently same. As the cold front meets the happens that an occluded front de- warm front a new discontinuity is velops into a well-marked cold front. formed which has a shape like a This may be explained by the fact wedge whose point rests on the that the occluded front represents a ground, and which slopes backward trough of low pressure into which or forward depending upon which there is convergence. On one side current is cooler, and known as a cold- of the front, say the eastern side, front occlusion and a warm-front oc- the air being drawn in is becoming clusion respectively. warmer and warmer while the air In the United States the air be- behind the front, drawn from the northwest and north, becomes colder hind the cold front is generally colder colder. In this manner the dis- than that ahead of the warm fr(;nt, and intensitied having had a shorter trajectory over continuity at the front is the of Wiirm relatively warm land areas. The oc- so that upper trough cluded front in this case will then air, which was originally responsible assume the form of a cold front in for the front, becomes insignificant its lower portion. If, as it sometimes compared with the new front which happens, the air ahead of the warm has been generated in the lower 36 AIR MASS ANALYSIS

layers. When this phenomenon oc- quite harmless, but later on may curs the occluded front may rightfully become important. In summer they

be called a cold front, (f ) illustrates may be the deciding factor (the the formation of this type of discon- "trigger action") in the formation tinuity, where the occlusion has been of thunderstorms. bent south in the rear of the cyclone (g) represents a vertical cross- (in agreement with the general air section through the line of AB in flow). The section of the front from (d). C to D gradually assumes the char- The following outline gives the acteristics of a cold front, while the general behavior of the meteorolo- section from D to E becomes a warm gical elements at the surface with front. When the occluded front bends the passage of the different fronts.

around as in (f ) it is called a "loop- These are, of course, average con- back" or a "bent-back" occlusion. ditions which are frequently observed The forecaster must be on the look- over the eastern section of the United out for the development of these States. Individual cases may show fronts; for a time they may appear quite different characteristics.

I f TABLE Meteorological Elements with ~Average Behavior of the Commonly Observed Front Passages Over the Eastern United States in Winter. Element Type of Front Passage: (at surface) Warm Front Cold Front (Cold) Occluded Front Pressure Falling, then steady Falling then slightly Falling slowly, then or falling less rapidly rising, then abrupt rising slowly rapid rise

Temperature Steady, then rising at Rising slowly, then Not much change, an increasing rate, falling slightly, then falling slightly after then steady dropping abruptly at front a rapid rate

Relative Humidity NORWEGIAN WAVE-THEORY 37

The Norwegian Wave-Theory of Cyclones^ B. Haurwitz* Meteorological Services of Canada, Toronto IN RECENT YEARS air mass analysis the origin of cyclones as frontal has been widely accepted by mete- waves can be strengthened and ac- orologists on this continent as a cepted only if it is proved that such basis for the study and forecasting atmospheric oscillations are actually of the weather. One of the funda- possible and do occur more or less mental assumptions of this method is generally in the atmosphere. the theory that cyclones form as Furthermore, the quantitative re- waves at surfaces of discontinuity lations between length and velocity between air masses of different origin of the cyclonic wave and temperature and history which, conseq^iently, have and wind discontinuity at frontal sur- different physical properties, e. g., faces can only be obtained by the temperature and humidity. mathematical theory. The verification The practical side of air mass of such formulae by observations analysis is well represented in this would represent the real check on booklet by Mr. Namias and Prof. the theory. Quantitative relations are Willett. The theoretical questions, further necessary since there exists whether waves actually can occur at sometimes a tendency to interpret such surfaces of discontinuity and weather situations without regard to whether these waves have any resem- the obvious niunerical impossibility blance to the nascent cyclones ob- of the proposed explanation. served in the atmosphere, have only Thus the wave theory of cyclones been touched slightly in their articles. presents a definite hydrodynamical They are, naturally, of secondary in- problem to the theoretical meteorolo- terest to the practical meteorologist. gist. He has to show that at frontal surfaces such as we observe in the The Problem atmosphere, waves can originate Perha,ps it might be argued that a which have the characteristic quali- mathematical study of the possibility ties of the cyclonic frontal waves of cyclonic waves is just a fruitless which are found on the maps; they pastime without any practical value. must possess a similar wave-length Are not cyclones in their earliest and velocity of propagation, and the wave-like stages found on almost motion of the air particles in the every weather map? However, before computed wave must agree with the the Norwegian school of meteorology air motion in the observed nascent conceived their idea of the origin of cyclones. Another very important cyclones as waves at frontal surfaces, point is that these waves must be no such phenomena noticed. If were unstable, i. e., their amplitude, at something appeared on the map which first very small, must increase with today would be interpreted as a time until the cyclone loses its wave frontal wave it certainly was formerly character and becomes a vortex. The never recognized as such. And even later vortical stages of the life his- now the wave theory of cyclones is ^This article first appeared in the Bulletin generally accepted. not Thus there A.M.S., June-July, 1937. can be no doubt that the theory of *Research Associate, Blue Hill Observatory. 38 AIR MASS ANALYSIS

tory of a cyclone (when the warm (disregarding the small ripples which sector occludes) have not yet been are subjected to capillary forces). attacked theoretically owing to the To understand better the physical extreme difficulty of the mathemati- process in a gravitational wave con- cal treatment. But the nascent wave- sider a mass of water which is lifted form has already been dealt with upwards from the original position vory thoroughly from a mathematical of equilibrium by a disturbance.

viewpoint. While it must be admitted This quantity of water has thus ac- that much still remains to be done quired a certain potential energy. on the mathematical analysis of the While falling back to its original young cyclone, as will become ap- place its potential energy is transparent later, it has been proved, formed into kinetic energy of motion. mainly by H. Solberg-^), that waves The velocity increases until the water postulated in the Norwegian (wave) passes through the equilibrium posi- theory of cyclone formation can and tion. However, it does not come to must exist in our atmosphere. rest but owing to the acquired veloci- In the following the results of the ty continues to move downwards mathematical theory will be repre- until the kinetic energy is trans- sented in a descriptive form. Readers formed again into potential energy. who desire to study the complete Then the mass element reverses its theory are referred to "Physikalische direction of motion and ascends. In Hydrodynamik" by V. Bjerknes and this way a wave motion is set up his collaborators'). Here the various which is damped out gradually only types of waves will be described by friction. This description applies which originate in a liquid or a gas to standing waves since it takes only due to different causes, and it will vertical motion into account. For be shown how these different causes progressive waves it would have to act together in the atmosphere to be modified slightly. Moreover, it give origin to the cyclonic waves. In is not quite satisfactory to single out this way we follow somewhat the one mass element and neglect the same line of attack as used by the motion of the surrounding water theoretical meteorologists. Owing to masses. These defects not withstand- the complexity of the problem it has ing, it shows that there is always a teen necessary first to disregard some transformation from kinetic to po- of the influences acting upon the tential energy and back in a gravita- Avaves in order to study somewhat tional wave, analogous to the oscilla- isimpler conditions. tions of a pendulum. Gravity Waves Similarly, the internal waves at A well known type are the waves the boundary between two fluid layers at a water surface, or, to be more of different density are gravitational accurate, the waves at the boundary waves. Waves of the gravitational between water and air. For wave type are stable as long as the original inotions of this type, the gravity of density distribution is stable. Un- the earth is the controlling force stable stratification is rarely found in the earth's atmosphere except near ^Bjerknes, Bjerknes, J., Solberg, H., and V., the ground, for obvious reasons. Bergeron, T. : Physikalische Hydrodynamik

Berlin, 1933, pp. 565-621 ; Hydrodynamique Therefore, gravity tends to generate Physique. Paris, 1934, 3 vols., Chapt. 14,

NORWEGIAN WAVE-THEORY 39

Compressibility and the waves are unstable. As we The compressibility of water is pass on to longer waves we come into comparatively small so that it can be a region where the stable stratifica- neglected in most cases. Atmospheric tion is more effectual than the shear- air, on the other hand, has a high ing instability. So now we are in the degree of compressibility. Under the region of wave lengths for stable influence of compressibility alone waves. The limit between shorter sound waves are obtained. The in- unstable waves and longer stable fluence of compressibility on atmos- waves lies at a wave length of at the pheric wave motions does not give most a few km under atmospheric rise to unstable waves as long as the conditions. It varies of course with lapse rate of temperature is below the order of the wind and tempera- the adiabatic, or for saturated air ture discontinuity. It will be seen the moist adiabatic. The considera- from this discussion that the unstable tions which lead to this conclusion waves of about 1000 km length re- are well known, and were given else- quired by the cyclone theory are not where in this booklet^) obtained when only the influence of Shearing Waves gravity, compressibility and wind shear are considered. If a wind discontinuity is present Inertia Waves in an otherwise homogeneous fluid, In order to find waves which re- waves are possible at this surface. semble the nascent cyclones of the These waves are always unstable in the effect of the earth's contrast to the wave types we have weather map rotation has to be taken into account. mentioned so far, which were only un- understand fully the importance stable if the stratification of the fluid To of the earth's rotation upon atmos- or the gas was unstable to begin with. The computation shows that the ampli- pheric wave motions we start out problem which at first tude increases more rapidly with time, with a simple seems quite devoid of any meteoro- or in other words, the wave is more logical application. Owing to its fun- unstable the smaller the wave length. damental significance it will be neces- Since the existence of this type of sary to deal with this case somewhat wave is due to the wind discontinuity in detail.^) If a hollow cylinder is or to the shear of the wind, it will partly filled with water and com- be called a shearing wave here, and pletely closed, then set in rotation we shall speak of shearing instability. the In the atmosphere, hardly ever do around a central vertical axis, was we observe a shearing discontinuity surface of the fluid which at rest will become parabolic. which is not associated with a tem- horizontal perature inversion and therefore a When the rotation is sufficiently fast, pressed completely density discontinuity.* When this is the water is so that the case, waves at the surface of dis- against the cylinder walls cyiindri- continuity must be of a mixed type, the liquid has a practically stabilizing gravitational since the *Even if no temperature inversion is present effect and the unstabilizing shearing there is still a certain degree of stability as long as the vertical temperature gradient is effect act at the same time. For less than the adiabatic. ^Namias, this booklet, pp. 4-8. small waves the unstabilizing effect ^Bjerknes, V. and Solberg, H. : Zellulare of the wind shear overcompensates Tragheitswellen und Turbulenz. Avh. Norske Via. Akad., Bd. I, Math-Nat. KL, no. 7, 3929, the stabilizing effect of stratification op. 116. 40 AIR MASS ANALYSIS

cal shape. The gravitational force is appears in the relation between velo- so much smaller than the centrifu- city and length of this type of waves, gal one that its effect is unnoticeable indicating that they are inertia waves. when the rotation is sufficiently fast. Some remarks on stability and in- Instead of the horizontal surfaces of stability of inertia waves are neces- liquids as ordinarily observed in sary in order to see their significance nature under the vertical action of for the wave theory of cyclones. To gravitation, the fluid in the rapidly choose the simplest case, which shows rotating cylinder has a practically the principle clearly enough, it may vertical surface due to the horizontal be assumed that a fluid mass rotates action of the centrifugal force. If around a vertical axis with an angu- this vertical surface is subjected to lar velocity q which is constant for a small disturbance a wave motion the whole fluid. If the fluid is en- wiU originate. This is quite analogous closed between rigid horizontal boun- to the case of gravitational waves on daries and situated at either pole of a horizontal surface of water, but the earth we have just the case con- in that case the energy of the wave sidered in the previous paragraph. motion was gravitational. In the The constant angular velocity of the present case of a rotating cylinder fluid is equal to the angular velocity the centrifugal force replaces the of the earth's rotation. An observer gravitational force. Since the centri- on the earth does not observe this fugal force is due to the inertia of "absolute" velocity since he takes the mass these are called inertia part in the rotation of the earth. waves by V. Bjerknes and H. Sol- The "absolute" velocity v at the dis- berg.*) tance r from the center is The existence of inertia waves in V = q.r a rotating fluid can also be demon- From the principles of mechanics strated by an elementary computa- it is known that the angular momen- tion. If a homogeneous incompressi- tum vr = q.r- of an individual parti- ble fluid like water is enclosed be- cle remains constant. Thus, if a parti- tween two rigid walls which are in- cle is pushed away from the axis, say finite in horizontal direction it can ircm the distance r to r + s, then the easily be shown that no wave motion constancy of the angular momentum

is possible as long as the fluid system requires that this particle in its new does not rotate. As soon as the ro- position must have a smaller angular tation is taken into account, as is velocity q' which is given by

necessary for the large scale atmos- q^-^ = q' {r -'r s)' pheric motions on the rotating earth, while the angular velocity of the sur-

it is found that now a wave motion rounding fluid masses at the distance is possible with a period longer than ?• + s is g as before. half a pendulum day. (A pendulum The centrifugal force acting on the day is equal to 24 sidereal hours di- displaced particle is vided by the sine of the geographic g'- (r+s) - q' -- = gV (1-3-) latitude, this being the t.me required {r-\-s)^ r for the swinging plane of a pendu- approximately, lum on the rotating earth to return while the centrifugal force in the sur- to its initial position.) Only the angu- rounding fluid at the same distance is lar velocity of the earth's rotation greater, namely, and not the acceleration of gravity

Thus the displaced particle has a With Bjerknes and Godske") we may deficit of centrifugal force which call this the "dynamic stability" due drives it back to its original position to the earth's rotation, while the where it is in equilibrium with its stability of the gravitational waves surroundings. Similarly when a parti- in the earth's atmosphere might be cle is displaced towards the axis it termed "static stability". obtains a surplus of centrifugal force Another important effect of the as compared to the surrounding fluid earth's rotation is the following. In and will again move towards its ini- purely gravitational waves the motion tial position. Thus the origin of iner- of the fluid particles takes place in a tia waves is easily understood. If a vertical plane, for the direction of particle is displaced outwards from the gravitational force is vertical. The its equilibrium position it is driven deflecting force of the earth's rota- back to this position. But while mov- tion, on the other hand, acts perpen-

ing back to the equilibrium position dicular to the earth's axis. Thus it it acquires kinetic energy so that it acts purely vertically only at the equa- approaches the axis of rotation more tor. At the pole it is directed hori-

closely than before the disturbance zontally, but at all other latitudes it until the surplus of centrifugal force is inclined to the horizon, so that we which the particle gains in approach- can speak of a horizontal and a verti- ing the axis overcomes the kinetic cal component. The vertical compo- energy and reverses the direction of nent generally can be neglected in motion again. The process is com- meteorology since its direction coin- pletely analogous to the wave motion cides with the far greater accelera- in the atmosphere in stable equili- tion of gravity. The horizontal com- brium, except that there the deficit ponent of the deflecting force of the or surplus in weight as compared to earth's rotation causes an inclination the surrounding air plays the role of of the plane of motion with respect to the centrifugal force. the vertical. The inclination is larger Earth's Rotation the greater the motion; thus in the It is obvious from the previous long cyclonic waves the motion is considerations that inertia waves in predominantly horizontal, while in a fluid rotating with constant angu- the small billow clouds it is vertical. lar velocity are stable. If our atmos- Cyclonic Waves phere were at rest with respect to Now that the different factors the surface of the earth, it would which cause and influence wave mo- appear to an extra-terrestrial observer tion have been considered separately to rotate with constant angular velo- it can more easily be understood how city around the earth's axis. In real- they act together to produce the cy- ity, owing to the different winds in clonic waves. the atmosphere, or, in other words, It was stated that according to the to atmospheric motions relative to Norwegian wave theory we have the earth, the atmosphere does not frontal surfaces between air masses "have strictly speaking a constant of different density (temperature, angular velocity. However, closer moisture content). Due to the differ- inspection shows that the wind dis- ent densities on opposite sides of the tribution in the atmosphere is such

''Bjerknes, J. ; and Godske, C. L. : On the that inertia waves of the dimensions theory of cyclone formation at extra-tropical fronts, Astrophysica •of cyclonic waves are always stable. Norve^ica, Vol. I. no. 6, 1936, pp. 218-219. 42 AIR MASS ANALYSIS

frontal surface the pressure gradients wave lengths of the order of 1000 and consequently the winds are like- km could only exist for infinitely wise different; these are observed small temperature discontinuities and facts. The observations also indicate impossibly large wind discontinuities, strongly that the cyclones originate according to the formula for billow from unstable waves on such frontal clouds. The fallacy of this objection surfaces. The possibility of unstable can now be seen immediately. In the waves with the characteristic dimen- investigation of the billow waves sions and motions found in nascent the influence of the earth's rotation cyclones, however, has to be proved. is neglected and can be neglected The theory shows that very small owing to the small dimensions. But waves are unstable up to a length of waves of cyclonic dimensions are a few lOOm, or, if the vertical strati- greatly modifled by the rotation of fication is not very stable, a few km. the earth around its axis. Exact figures can not, of course, be Thus, the wave motion becomes given as long as the density and with increasing wave length more and wind distribution are unknown. The more inclined to the vertical under limit between stable and unstable the influence of the deflecting force waves depends on the lapse rates of of the earth's rotation. This leads temperature in both air masses, and to the formation of unstable waves on the temperature and wind dis- in the following way. The stable continuities at the frontal surface. character of gravitational waves in But it can be stated that for suffi- the earth's atmosphere depends on ciently small waves the shearing in- the difference between the weight of stability (wind discontinuity) is more the oscillating particle and that of effective than the gravitational sta- its surroundings and thus on the ver- bility. In other words, very short tical component of the oscillation. waves are unstable and have more Consequently, as the waves become the character of shearing waves than longer and the w^ave motion more of gravitational waves. For the theory horizontal the stabilizing effect de- of the cyclone these waves are evi- creases, since the vertical component dently far too short. When the waves of motion decreases. The computa- are longer the stabilizing influence tion shows that waves whose length of gravitation becomes more pro- is of the order of 1000 km are unstable. nounced so that beyond a certain At such wave-lengths the shearing in- critical wave length the waves will stability is greater than the gravita- be stable, because the effect of shear- tional stability (which is small) owing ing, which tends to produce instability, to the almost horizontal motion of decreases with increasing wave length the particles. But with still longer and is over-compensated by the sta- waves the shearing instability be- bilizing effect of gravitation. The comes smaller than the dynamic sta- gravitational-wave character is now- bility caused by the earth's rotation predominant. Billow clouds are waves and, therefore, such waves become of this type. stable again. The wave length of billow clouds It is obvious that the only waves is the greater, the smaller the tem- which may be regarded as cyclonic perature discontinuity. From this it are the unstable ones whose length has been concluded that the wave is of the order of 1000 km. They theory of cyclones breaks down since are of a mixed type because, in addi- .

NORWEGIAN WAVE-THEORY 43

tion to shearing instability, gravita- gation is therefore called the "con- tion and inertia act upon them. vective" term. The second term, The mathematical analysis also which is due to the dynamical pro- shows that these waves have veloci- cesses of the wave motion, is referred ties of the order of magnitude ob- to as the dynamic term. served in nascent cyclones, that the Remaining Problems velocities are generally directed east- While the wave theory is suffi- wards, and that the motion of the ciently far advanced for one to say air is of the type found on the with certainty that cyclonic waves weather chart. Therefore, we can occur in the atmosphere, much re- say that the theory shows that the mains to be done yet. The investi- formation of a cyclone from waves gations so far have been dealing with not only is possible but rmist occur in wave motions at the boundary be- the atmosphere because the waves tween isothermal air masses, because are frequently unstable and there- isothermy gives equations which are fore form spontaneously. Of course, easier to handle than equations which stable waves also occur; if they are take the usual linear temperature much shorter than cyclonic waves gradient into account. But isothermal they are observed as billow clouds, lapse rate implies, obviously, a larger ceiling fluctuations, and microbaro- stability of atmospheric stratification metric oscillations, and if longer than than is ordinarily found, so the nu- cyclonic waves (and thus stable again merical results will have to be modi- owing to the stabilizing influence of fied. Notable advances in this direc- inertia) they appear as flat frontal tion have recently been mode by H. waves like young cyclones, but never Solberg.') Furthermore, note that a develop into mature cyclones. (See sharp discontinuity of wind and tem- Fig. 9.) perature is assumed in the theory while in reality a narrow transitional The theoretical investigation of zone exists in which the elements cyclonic waves shows further that the change rapidly but continuously. It velocity of propagation consists of has been shown, however, that the two terms. Their physical significance wave is practically the same whether is understood most easily by con- there is a sharp discontinuity or a sidering a wave on the surface of a transitional zone, provided that the river. The propagation of such a thickness of the transitional zone is wave is partly due to the bodily trans- small compared with the wave length') port of the oscillating water masses This condition is always fulfilled for by the flow of the river, the "con- cyclonic waves. vective" term, and partly due to the A certain deficiency of the wave motion of the wave relative to the theory of cyclones in its present state, water, the "dynamic" term. Similar- which we tactfully have not men- ly, the first term in the expression tioned so far, is the assumption that for the wave velocity at a surface of the lower cold layer and the upper discontinuity is due to the mean motion of both air masses. It simply "H. Solberg : Schwingungen und Wellenbe- wegungen in einer Atmosphare mit nach oben indicates the fact that the is wave abnehmender Temperatur, Astrophysica Norve- transported passively due to the un- gica, vol. 2, no. 2, 1936, pp. 123-172. 'Haurwitz, B. : Zur Theorie der Wellenbe- disturbed motion of both layers. This wegungen in Luft und Wasser, Veroffentl. d. part of the total velocity of propa- Geophysikal. Inst. Univ. Leipzig, Spezialarb., Ser. 2, Vol. V, no. 1, 1931, pp. 52-53, 73-74. 44 AIR MASS ANALYSIS

(Fig. 10). Solberg^) has given some preliminary results but the problem is so extremely difficult that until now a somewhat round about approach has been used. Waves of the cyclonic type in the layers parallel to the frontal surface and therefore inclined to the horizontal according to Margules' formula^), have been Ry.i studied. It was found that some of the "stream surfaces" along which the motion of the air particles takes place are practically horizontal planes for an extent of about 2000 km or more (Fig. 11). Now a stream surface can be assumed to be rigid, since according to the definition of a stream surface the motion is paral-

lel to it. If we let the stream surface in Fig. 11 become solid and regard it as the surface of the earth a very close analogy to the atmosphere is obtained in the region near the intersection between stream surface and surface of discontinuity. The cold air lies like a wedge under the

Fig. 1. (9) Vertical Cross Section warm air and the wave motion near Through a System oe Two Air the surface is almost parallel to the Masses with Parallel Boundaries solid horizontal stream surface, which Separated by a Surface of Discon- tinuity, AS Considered by the may be identified with the surface of Theory. The Boundaries and the the earth. Farther away from the Surface of Discontinuity are In- frontal surface the agreement with clined Against the Surface of the Earth. reality is of course less satisfactory, since the curvature of the solidified Pig. 2. (10) Vertical Cross Section Through the Actual Position of stream surface will be stronger. But Warm and Cold Air Masses Relative the intensity of the wave decreases TO the Surface of the Earth. with the distance from the surface Fig. 3. (11) Same as Fig. 1 with a of discontinuity. The field of motion Stream Surface Which Runs Partly Horizontal Over This Approxim- is dynamically most important at the ately Horizontal Area (Indicated front, and loses its significance com- BY the Rectangle) the Stream Sur- paratively rapidly in lateral and ver- face May be Regarded as the Sur- tical directions. Therefore the method face of the Earth. of assuming solidification of a hori- warm layer have boundaries parallel zontal stream surface is more satis- to the frontal surface (Fig. 9). In factory than might appear at first. reality, the frontal surface intersects ^Solberg, H. : Integrationen der atmospharis- the surface of the earth so that the chen Storungsgleichungen (I), Geofys. Pm6Z., vol. V, no. 9, 1928, pp. 104-120. cold mass has the form of a wedge 'Namias, this booklet, p. 25. NORWEGIAN WAVE-THEORY 45

Nevertheless it will be necessary pected that the curvature of the earth to solve directly the problem of a has a certain influence. In this re- wave motion at a frontal surface in- spect also much remains yet to be clined to the surface of the earth, done. But the possibility of cyclonic especially in order to obtain reli- waves in our atmosphere can be re- able quantitative criteria to decide garded as proven in spite of these whether an observed wave is stable gaps in the theory, and it can safely or unstable. be said that objections to the wave Finally, cyclonic waves have thus theory of cyclones result from in- far been investigated only on a ro- sufficient knowledge of the theoreti- tating plane. Considering their di- cal investigations. mension, however, it is to be ex-

Frontal Waves

lb.

1 46 AIR MASS ANALYSIS

"Labilitatsenergie" in the ter- increasing amplitude. This conver- minology of Refsdal.t gence implies in its turn an increase It is shown that the lability en- of cyclonic circulation within this •ergyt though smaller than the cur- area, which again involves a fall of rent and frontal energy, probably pressure in the middle of it, com- plays a great role in cyclogenesis, be- pensated by a slighter general rise cause it may get stored up a" long of pressure in the outskirts of the time beforehand over a rather great disturbance." {Bull. Amer. Met. Sac, at the most area, and only released Sept. 1937, p. 269.) favourable moment and in the very center of the cyclogenesis, v^rithout much frictional loss of energy. t According to Refsdal ("Der feuchtlabile Niederschlag", Geofy. Publ, Vol. 5, No. 12, author has tried to form a The 1930, p. 9) the "lability energy" of an air more concrete idea of the mechanism mass is defined as the maximum amount of of cyclogenesis, i.e., of the fall of energy which could be set free by an over- pressure around the "warm tongue" turning or an upward motion of this air mass. The "lability energy per unit mass" between increasing am- of a frontal wave of two heights is the algebraic sum of the work plitude. produced when a particle of unit mass is This mechanism should consist in a raised from the lower to the higher level (the compensating downward motion of the sur- centre of gravity of sinking of the rounding air being spi-ead out over an in- the whole system under considera- finitely great area). This is conditional in- tion, conditioned by that ascent and stability, including the instability realizable by condensation of water vapor. Compare with air at the convergence of warm discussion of energy in Articles on the Tephi- *'warm tongue" of a frontal wave of gram and Thunderstorm.

A Note on Dynamic An ticyclones and Cyclones In the discussion of American air masses namic process which piles up air in the upper

It is pointed out that cold Pc air is character- or middle troposphere or to a northward istically shallow. In fact the majority of advection of cold (tropical) air in the strato- moving anticyclones on American weather sphere over the anticyclone, suflScient to maps are of the shallow so-called cold (or overcompensate the lowering of pressure from polar) type, having warmer Pm or Tm air warming in the troposphere. The warm (with often even low pressure and cy- highs are common in western Europe, where clonic winds) aloft.* Wexlert has shown why the cold-stratosphere advection theory for the radiational cooling in the polar regions their maintenance has been generally ad- does not succeed in building up a very deep vocated in recent years. Indeed, some Euro- layer of Pc air before it is released to lower pean caS;S** have been studied (from sound- that may tremendous rise in latitudes ; the upper warm layers ings) where apparently a move south bodily with the Pc are thus Pm or Stratospheric pressure caused a marked day Tm air still unmodified to Pc. Subsidencet to day rise in the surface pressure of a cold usually greatly accentuates the upper warm- anticyclone while it was becoming warm (a it yet ness of these cold-type highs as they move common phenomenon) ; but has not southward. Figs 3-6 herewith, from Haurwitz been proven that this was more than a coin- and Noble, show a case of a cold surface high cidence rather than some necessary conse- replaced by low pressure aloft. Note, how- quence of the effect of tropospheric pressure ever, that this is in part due to the backward changes in inducing stratospheric advection slope in the free air of the axes of the lows, or vice versa. In an American case studied by since the lowest pressure is always at the cold front at any level and the front itself Noble, Bull. Amer. Met. slopes backward. *Haurwitz and Soc, March, 1938, pp. 107-111.—A good exam- so-called warm anti- However, there are also ple : J. Namias, Structure of a We-dge of cyclones which in most cases seem to have Continental Polar Air. M. I. T. Met. Course, Prof. Notes No. 6, 1934. developed from cold ones after the latter have tH. Wexler, Mon. Wea. Rev.. April 1936, p. slowed down and suffered heating from 122-135. and June 1937, pp. 229-236. below in middle latitudes. Since these highs tj. Namias, Subsidence in the Atmosphere are warmer than cyclones from the surface Harvard Met. Studies No. 2, 1934. ** up to high levels (8 km or more) the main- H. Thomas, Sitzber. Preuss, Akad. Wiss., 1934 ; Khanewsky. anticyclonic winds and the Phys Math. Kl. vol. 17, tainance of their Met. Zeit.. Met. Zeit.. 1929, p. 81 ; Runge, "high surface pressure cannot be explained Geophys. Inst. 1932, p. 131 ; Schmiedel, Veroff. thermally. It must be due either to some dy- Univ. Leipzig, vol. 9, no. 1. DYNAMIC ANTICYCLONES 47

Fig. 3. Pressure distribution at sea level Fig. 4. Pressure decrease in first 5,000 feet, (mb), February 3, 1937, 8 a.m. February 3, 1937, 8 a.m. Fig. 5. Pressure distribution at 5,000 feet, Fig. 6. Pressure distribution at 14,000 fbet, February 3, 1937, 8 a.m. February 3, 1937, 8 a.m. (The dotted circles show the position of the surface Highs)

Simmers* using isentropic analysis, a warm rather their paths just happened to intersect. upper-level anticyclone over Texas and a cold Probably there are various possible types of one moving down from Canada amalgamated. anticyclogenesis. The warm anticyclone built up from middle to Cyclones also occur in warm and cold types. high levels isentropic mix- through a process of The usual open warm-sector or freshly-oc- ing which transferred air across isobars cluded low contains a warm core, but fre- ("banking effect" described by Namias in his quently an occlusion develops into a deep chapter on Isentropic Analysis). The resulting slowly-moving vortex without fronts but cloudy convergence caused the surface pressure to

and with precipitation ; soundings will show continue to rise, although the cold anticyclone the core to be colder than the surroundings up was being dissipated by surface heating. This to hi^'h levels, even to the stratosphere, which was in May and there was no evidence the may be sucked down and warmed, thus help- warm anticyclone gtew from the cold one, but ing to maintain the surface low. These cold *R. G. Simmiers, in: Fluid Mechanics Ap- cyclones occur particularly in the regions plied to the Study of Atmospheric Circulation, where cyclones usually have reached the oc- Part I, Pavers in Phys. Oceanogr. and Met., rrcA. 8. 1938. cluded stage, in the higher latitudes of the 48 AIR MASS ANALYSIS

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50 AIR MASS ANALYSIS

Atlantic and Pacific for example ; they are sub-tropical anticyclones (e.g., Azores High) notable in spring in eastern XJ. S., too. are also warm and dynamic in character The existence of "dynamic" lows and highs the moving anticyclones of middle latitudes does not refute any principles of frontal or often finally merge into them. However, the air mass analysis, however uncertain the the- Aleutian and Icelandic semi-permanent Lows oretical explanations, but such phenomena are more statistical than dynamic, due to fre- must be recognized as additional processes to quent frontal cyclogeneses, though deep dyna- be given due consideration in forecasting. mic lows often stick there for days at a time. It might be added that the semi-permanent R. G. Stone.

The role of the tropopause in the dynamics of extra-tropical disturbances

"J. Bjerknes has especially studied the in- genesis ("Verwirbelung"^the transformation teraction between waves in the Polar Front of a frontal wave into a vortex ) , when the surface and waves of the tropopause, showing suction effect of the "circular vortex" (ac- that the latter cannot be the primary ones. cording to V. Bjerknes, 1921, sinking in According to J. Bjerknes these induced tropo- cyclones, lifting in anticyclones) will be most pause waves mainly consist in a horizontal pronounced and a "new tropopause" has not meridional oscillation of the air at the oblique yet had time to form at the normal height. tropopause. The advective effect of J. Bjerknes, on the E. Palmen adds to the above effect also the other hand, will most likely predominate not pumping effect of cyclones and anticyclones only during the initial wave-like stage of to which the stratosphere is subjected, using Polar Front disturbances but also during their aerological data to show that the tropopause final stage, when the violent pumping effect is often lower, the stratosphere temperature of the "Verwirbelung" may have developed higher, in deep cyclones of our latitudes than a kind of free oscillations of the tropopause, in Arctic regions in winter. §uch a state which liberate themselves from, the tropospheric could not be attained merely by advection of vortex and are propagated in the ordinary the low and comparatively warm Arctic strato- way eastwards.—These initial and final stages sphere, but the stratosphere must also be are of much longer duration and are also pre- sucked down by the cyclonic vortex (and by dominant in intensity as compared with the analogy pushed up in anticyclones). stage of "Verwirbelung" in those rather low The author then proposes the following solu- latitudes from which the statistical data of tion, which takes account of both effects and Dines and Schedler were collected. This may also satisfies the well-known statistical data explain why the statistics quoted speak in from the upper air of Dines and Schedler. favour of the advective effect, whereas the The suction effect of Palmen ought to pre- intense high latitude cyclogeneses studied by dominate during and shortly after the most Palmen show all the characteristics of the intense processes of cyclogenesis or anticyclo- suction effect." T. Bergeron.

VIII. THE TEPHIGRAM*

In order to forecast local showers would be fruitless. Because of this and thunderstorms successfully it is control of the weather by local upper- necessary to interpret aerological air conditions, forecasters now con- data in the light of a reliable analysis sider upper-air soundings almost in- of the synoptic chart. An individual dispensable in summer work. In order sounding made in the lower tropo- to portray most effectively the state sphere is more immediately signifi- of the upper atmosphere, particularly cant in summer than it is during the from the standpoint of energy trans- winter months. That is, in the warm formations, several diagrams have months upper-air conditions imme- been suggested. diately above a station are relatively Hertz developed a diagram (later important in determining the weather modified by Neuhoff ) on which an aero- for the particular day, whei-eas in winter the rapid advection of air *The procedures with the tephigram described herein may be readily applied to other masses may so completely change the thermodynamic diagrams such as the modified pseudo-adiabatic charts of the U. S. Weather upper-air conditions over any given Bureau (Upper Air Map C and forms 1147 point that an attempt to forecast and 1126 Aero.) described in Article III, p. 18, to the Refsdal emagram and "Aerogram", solely from the data in one sounding and to the Neuhoff diagram. THE TEPHIGRAM 51

logical sounding might be plotted so hardly doubt the existence of rela- that one could trace the path of any tively small, rapidly rising up-cur- chosen particle of air as it ascended rents, called by the gliding enthu- or descended through the surround- siasts "thermals". ing medium, in this manner making The tephigram, with which we shall it possible to see if work is being here be concerned, acquires its name •done by the rising air particle or if from the thermodynamic quantities it is necessary to supply mechanical that are its coordinates: temperature energy in order to make it rise. This (T) and entropy ((^). The term diagram, which has long since found entropy I shall not attempt to define a niche in classical meteorology, here, for it is a concept which defies forms the basis of modern attack on descriptive definition, and is a sort problems of the upper air through of mathematical adaptation. Its deri- energy diagrams. The emagram and vation may be found in any textbook aerogram of Refsdal' and the tephi- on thermodynamics. Generally, the gram of Shaw' * have superseded the synoptic meteorologist regards en- Neuhoff diagram because of greater tropy as something which is propor- simplicity in usage and adaptation. tional to potential temperature, for Whatever the type of energy dia- it may easily be shown that: gram used it is important to note at d, — C log 8 + constant (1) ^ p the start that in all of them it is where is the specific entropy of dry assumed that one and only one ele- ^ air, C the specific heat of air at con- ment of air rises in some manner p through the stationary environment. stant pressure, and the potential Thus the indications expressed in the temperature. The choice of a value diagram will depend in no small man- for the constant is entirely arbitrary, ner on the properties of the particular for, as with energy, it is not the abso- chosen particle. Actually the inte- lute value of entropy that matters, grated effect of the large number of but rather the changes. particles making up the air column Entropy is used as the ordinate of should be considered. There is some the tephigram. Because of the re- doubt as to whether it is justifiable lation and the ease of obtaining to neglect several other factors which (1) 0, the logarithm of the latter is often may conceivably enter into the pro- used as an ordinate in addition to cess. The ascent may be in the entropy. The abscissa of the tephi- nature of lifting of an entire layer gram is temperature, usually ex- rather than the rising of a "bubble" pressed in degrees C. In the diagram of air, small compared with an air shown in Fig. 13 the temperature in- mass. Then there are the non-adia- creases from right to left; in some batic effects of radiation. In spite of the diagram this scale is re- of the complete neglect of such com- types versed (Fig. The solid lines plicating factors, energy diagrams, 15). based on the assumption that one ^A. Refsdal : Der feuchtlabile Niederschlag,

relatively small mass of air rises Geofystske Publikasjaner, Vol. 5, No. 12, 1930 ;

Das Aerogram, Met. Zeit., Jan. 1935, pp. 1-5 ; through a more or less steady en- Geofys. Publ., vol. 11, No. 13. vironment, have been used success- ^Sir Napier Shaw: Manual of Meteorology, Vol. Ill, The Physical Processes of Weather, fully. This fact per se indicates that Chapt. 7, Cambridge, 1930. Cf. Woolard _et

: Thermodynamics of the Free Air, the fundamental assumption is in al Graphical Mo. Wea. Rev.. Nov., 1926, pp. 454-457. the main justified. Furthermore, *C. M. Alvord and R. H. Smith: The Tephi- anyone who has had the opportunity gram, M. I. T. Met. Course, Prof. Notes No. 1, 1929 (out of print). Repr. Mo. Wea. Rev., to witness gliding activities can Sept., 1929, pp. 361-369. 52 Am MASS ANALYSIS sloping downward from the left to fic humidities at the significant levels right are lines of equal pressure. against the corresponding pressures, From Poisson's equation it is readily which is more convenient than com- seen that these isobars are defined by puting dew points and gives precisely the rectangular coordinates: potential the same result. The depegram for temperature and temperature. In the the Oklahoma ascent is represented diagram reproduced here (Fig. 13) in Fig. 13 by the dotted lines con- the isobars are expressed in milli- necting crosses. From the tephigram meters of mercury; more frequently one may easily determine the stability the unit used is the millibar. Broken of any given stratum, for the hori- lines sloping slightly to the right of zontal lines, being lines of constant the vertical are lines of equal specific potential temperature, are dry adi- humidity (on some diagrams the mix- abats; the vertical lines, isotherms; ing ratio is used instead), the values and the curves sloping upward from being the saturated mass of water left to right are saturated adiabats. vapor in grams per kilogram of moist Thus the layer EF possesses a dry air which can exist under the ap- adiabatic lapse-rate, AD contains a propriate temperatures and pres- temperature inversion (probably a sures. The solid curved lines sloping ground radiation inversion), and the upvv^ard from the left to right are layer DE is in conditional equilibrium pseudoadiabats — lines which repre- as the lapse-rate lies between the dry sent the path of a rising saturated and the saturated adiabats. The depe- particle of air precipitating its mois- gram enables one to get a picture of ture as soon as it is condensed. Nota the relative dryness of the various how the slope of these curves ap- layers. For example, the surface proaches the horizontal lines of equal layer at A is almost saturated, for potential temperature (the dry adia- here the dew-point is nearly equal to bats) at low temperatures, because of the temperature. Above the point E' the decreasing saturation humidity the air is very dry, a fact shown by content as absolute zero temperature the comparatively large distance be- is approached. tween the temperatures at E, F, and There are several ways to plot a above, and the dew-points at these tephigram, the most convenient de- levels shown at E', F', etc. pending upon the quantities one has The most important use of the at hand. For example, it is possible tephigram lies in indicating the to use the rectangular coordinates, amount of potential energy, in the potential temperature and tempera- overlying air column, which may be ture; then again one may plot tem- converted into the kinetic energy of perature against pressure by using a thunderstorm. For this purpose it for coordinates the slanting isobars is necessary to choose some individual and vertical isotherms. In Fig. 13 is particle of air and follow by means plotted the sounding for Oklahoma of the diagram the path it would take City on June 20, 1935; this is the if subjected to vertical displacement solid line, the significant points of up through the entire air column. It which are small circles, A to H. In is assumed that the surrounding air conjunction with the tephigram it is remains at rest while this displace- also helpful to construct what is ment of a unit element of air is known as a depegram—a curve show- taking place. It might be assumed, ing the variation of dew-point, and for example, that the point A is car- hence of moisture, with elevation. ried upward. In this event the par- This is constructed by plotting speci- ticle of air represented by the point —

THE TEPHIGRAM 53

Figure 13. Tephigram for Oklahoma City, June 20, 1935 Early A.M.

A would at first cool along the dry slope upward slightly to the right of adiabat; that is, it would trace on the the vertical. Consequently in order tephigram a horizontal line. But this to find the point of saturation one could go on only until saturation has merely to trace a line horizontally occurred, for beyond this point the from the originally chosen point on sample of rising air would no longer the tephigram until it intercepts the cool at the dry adiabatic rate but at line of saturation specific humidity the rate of expansional cooling for passing through the corresponding saturated air given by the pseudo- point of the depegram (that is, adiabats. With the help of the through the specific humidity of the diagram this point of saturation is original particle). Thus the hori- readily determined. As the particle zontal line from A would continue to ascends the mass of water vapor per the right until it meets a line drawn unit mass of air (the specific humi- through A' parallel to the 15 g/kg dity) remains constant until condens- line of saturation specific humidity. ation begins. When saturation is Beyond this point the rising particle reached the specific humidity of the follows the curved pseudoadiabats. rising particle is the maximum This process will be clarified by select- amount of moisture possible at that ing some other point from which a temperature and pressure. These parcel of air would logically be more lines of maximum (or saturation) apt to rise through the air column. specific humidity are given in the The ascent plotted in Fig. 13 was tephigram by the dashed lines which made in the early morning; thus the :

54 AIR MASS ANALYSIS

large inversion in the surface layers changes in air-mass properties. Con- is for the most part a radiation in- sequently there still remains in the version. Under the effect of insola- layer KD a portion of the original tion as the day progresses the air ground inversion. Now if a particle near the ground may be expected to at J is forced to rise, following the warm up considerably. Therefore the path KL, its temperature at each level point A will be transferred to higher (defined by a particular isobar) and higher temperatures while the would be lower than that of its sur- pressure remains essentially the same. roundings. In fact, even after satu- Thus A moves along the 720 mm iso- ration at L the rising particle would bar until the maximum temperature remain colder than its environment is reached. It is for the forecaster until the point M when the tempera- to decide what this value is most tures of the rising air and its sur- likely to be. In this case let us say roundings would become just equaL that the temperature will rise to Throughout the layer from K to M 35°C (95°F). A is thereby shifted work is required to lift a particle along its isobar to J. Let us con- forced upward from K. The amount sider that there is no addition or of energy required for this purpose subtraction of moisture so that the may be shown to be equal to the specific humidity remains constant at vertically hatched area KLMEDK. On about 14 g/kg. Then as J rises its the original scale of the diagram from path is given by the dashed line; it which Fig. 13 is reproduced, 1 square follows the dry adiabat until its tem- cm is equivalent to 2 x lO'* ergs per perature falls to the value where the gram; in Fig. 13, 1 square cm is- specific humidity (14 g/kg) is the equivalent to 3.3 x 10* ergs per gram. saturation quantity. Thus J is moved Beyond M, a rising particle, follow- horizontally until it intercepts the ing the pseudoadiabat MN at every 14 g/kg moisture line at L. Beyond stage in its ascent, would be warmer L the path of a rising particle is than the surrounding air. In this given by the pseudoadiabat LN. manner, after reaching M. it will rise- The lapse-rate in the surface layer of its own accord, so to speak, for has been materially changed since the it is now less dense than the air com- morning hours, and in view of con- posing its environment. From energy vective mixing it is safe to assume considerations it may be shown that that a dry adiabatic lapse-rate has the energy liberated by a unit ele- been established up to the point K. ment of air rising from M to N is Along JK there is neutral equilibrium given by the horizontally hatched with respect to dry air. That is, a area MFGHNM. particle of air along JK that is ver- (In practice it is customary to color tically displaced is neither assisted in red the horizontally hatched area nor resisted by the density distribu- and in' blue the vertically hatched tion. But while this adiabatic lapse- area.) rate is built up, the structure of the To generalize air aloft, barring any change of air- Where the path of a rising particle mass properties, remains essentially lies above the tephigram of the sound- unchanged. Thus above K, the point ing, energy is available for producing of intersection of the isentropic line overturning, which may result in and the original sounding, it is thundershowers, and the amount of assumed that there are no major this energy is given by the area {in THE TEPHIGRAM 55

this case called positive area) en- small negative areas are most favor- closed between the path of the rising able for the development of a particle and the tephigram. thunderstorm. While there is no sub- When the path of a rising particle titute for experience in working with lies below the tephigram of the sound- the tephigram, it is possible to make ing, stability is indicated, and the some statements of a general nature area (called negative area) enclosed which should assist the beginner in betiueen the path of the rising particle his use of the tephigram. Such a and the tephigravt represents the discussion, consisting of the indica- amount of energy which must be over- tions and limitations of the tephi-. come if the particle is to penetrate gram, particularly when used in con- the layer. junction with a reliable weather map From these considerations it is analysis, is taken up in the article on clear that large positive areas and Thunderstorms, below.

A Note on Estimating Conditional and Convective Instability From the Wet-bislb Curve Normand* has called attention to can be compared with the saturation the fact that the usual method of in- adiabats just as the temperature- dicating humidity by a depegram shows height curve can be compared with the only the variation of humidity in a dry adiabats. Drawing conclusions con- sounding, and that it cannot be used cerning the "liability" to instability directly for visualizing the amount of from a tephigram alone by comparison energy available in a particle of air of the latter with saturation adiabats which rises from some particular layer. is undesirable, for if the air is dry at He pointed out further that in order all heights it is a waste of time to to make reasonably correct deductions consider it as if it were moist. When about the stability of such a particle of that method is used it is the same as rising air, it is desirable to have a assuming that it is possible by a mete- thermodynamic representation of hu- orological process to saturate dry air midity on the tephigram as well as one without altering its temperature! But for temperature. In order to obtain it is well known that dry air which such a representation he has advocated passes over a large lake or the ocean that the saturation (in practice, the does not become saturated without a wet-bulb) temperatures of a sounding simultaneous change in its tempera- be plotted on their appropriate isobars. ture. It is necessary when estimating This method is a natural sequence of the probable effect of an increase in the use of wet-bulb temperatures of humidity to assume a decrease in dry- the free air first advocated by him in bulb temperature, an increase in the 1921. He argued that the "saturation dew-point, and little change in the temperature" curve (S.-T. gram; or wet-bulb temperature. This is the most estegram) of a sounding should important justification for including a be used because the tephigram and wet-bulb or saturation temperature depegram alone do not consider the curve (these two curves are practi- actual state of humidity, and because cally equivalent to one another) along-

it is desirable to have a curve which side the tephigram in estimating "liability" to instability. * Normand, C. W. B.: Graphical indication Normand has found the addition of air, 3rd of humidity in the upper Nature, the October, 1931, Vol. 128, p. 583. the wet-bulb temperature curve on f

56 AIR MASS ANALYSIS

tephigram permits a more clear-cut no7' pseudo-instability. In other words, classification of tephigrams according there is no energy realizable at all. to vertical stability. In tropical re- A particle of air has latent insta-

gions the state of conditional instability or pseudo-instability , if the bility generally prevails, and in middle saturated adiabat through it (for ex- latitudes it occurs rather frequently. ample, the initial position of the Sometimes, however, it is associated particle tinder consideration) on the with settled weather and sometimes wet-bidb curve intersects the curve of with disturbed; in studies made in the tephigram. The latent instability India the tephigram alone gives no can be realized, however, only when criterion which allows a correlation the amount of work which must be with the type of weather. The Indian done to raise a particle of air to the meteorologists found, however, that condensation level (from which it the important criterion in that connec- would thereafter rise freely) is less tion is the vertical distribution of than the energy which will be realized water vapor, and that a wet-bulb curve during its further ascent (i.e., only in

drawn beside a tephigram gives a more the case of real latent instability) . If definite picture of the amount of the saturated adiabat through the energy that is likely to become avail- point of the initial wet-bulb tempera- able as a consequence of convection ture of the particle under considera- reaching the condensation level. tion does not cut across the line of the The use of estegrams together with dry-bulb temperature, then no upward tephigrams makes it possible to clas- displacement of the particle can bring sify the conditions of particles of air it to a level where it will be as warm with respect to their environment into as its environment, so then the atmos- three classes of conditional instab- phere is stable for all particle displace- ility :— ments—large or small. 1) Particles of air which if raised In order to release the energy in air adiabatically will release more energy which is in a state of latent or pseudo- in the upper unstable portion of their instability a trigger action is neces- ascent than must be supplied to them sary, notably surface heating, and in their lower, stable portion, are in a surface evaporation, but also lifting state of (real) latent instability. by a cold front, a mountain, or by 2) A case in which a particle can be convergence; release by lifting how- raised with a given supply of energy ever, is strictly a case of convective to a position where it is in an unstable instability in which of course whole- environment and thus some of its sale release of conditional instability energy can be liberated, but the energy is an intermediate process (see below). so liberated is less than that supplied The recognition at a glance of the from below, is termed a state of layers in which all particles have pseudo- (latent) instability. pseudo or latent instability is easy 3) In the third case, when the lowest when the wet-bulb curve is entered saturation adiabat tangential to the beside the tephigram. For instance, tephigram does not intersect the este- in Figure 14 the layers with latent gram, there is neither latent instability instability are determined by ex-

t Normand first defined the concept of tending the moist adiabat which is latent instability in an article on tropical tangential to the portion of the tephi- storms in Gerlands Beit. z. Geophys., Vol.

34, p. 234, 1931 ; the principle is examined in gram which approaches the wet-bulb detail by him in the Q. Jn. Roy. Met. Soc, 1938, p. 47, f£. curve most closely down to the surface THE TEPHIGRAM 57

V' 58 AIR MASS ANALYSIS

of Brunt (Phys. Dyn. Met., p. 45), a lapse The fact that dust or thunderstorms do not rate of 11.3°/gkm between surface and 1 gkm occur more frequently than they do, although would be enough to cause (absolute) instabil- the vertical temperature gradients in the lower ity in the layer. Even up to 1.5 gkm condi- levels may be adiabatic or superadiabatic day tions of lapse rate favorable for instability after day in the summer months over Agra is exist on this day, the actual rate being probably due to the want of the necessary 10.7° /kkm, whereas the critical (neutral) rate condition, viz., latent instability. is 10.3°/gkm. In any case, the layers up to In this sounding all particles up to about 1 km are definitely unstable. These conditions 460 mb are latently unstable, an extreme case ; would provide a "trigger" of sufficient magni- the level of greatest latent instability is at tude to initiate displacement of the lower about 880 mb, but since the convection is layers. obviously taking place from the heated sur- It is seen that particle a from A starting face, the proper analysis is to consider the on account of instability in that layer will energy areas for a rising surface particle. gain energy in the initial portion of the The decrease of wet bulb below 900 mb indi- asaent up to B (794 mb). The gain is cates that a surface particle has considerably AFBMA. After B, the ascent up to D would less latent instability than a particle say at involve a loss of energy BCDEB. It is only 880 mb whose condensation level would be at if the particle can reach D (500 mb), that it 750 mb giving a smaller negative area and will come into the environment of latent in- far larger positive area than for the surface stability and begin to gain energy ; and it particle. The same would be true for particles can reach D only if BCDEB is less than up to around 620 mb. Mixing in the lowest AFBMA. But actual measurement of these areas 300 mb layers will increase the surface wet- shows that BCDEB is slightly greater than bulb, however, and tend to distribute the AFBMA, being roughly in the ratio 14 :11. latent instability more equally among the dif- This is what one would expect, if one re- ferent levels, in these layers. If this sounding members that the meteorograph was sent up were an early morning one, the latter consi- only 5 minutes before the occurrence of the deration would certainly deserve some weight third squall, there being a comparative lull in estimating the realizable latent instability between the second and third squalls. During for later in the day. five minutes the meteorograph could have In many cases, however, the wet bulbs are ascended only about 1 km. So, it is only up much lower, relative to the dry bulb, at the to about a km above ground that the tephi- upper levels than in this sounding, with only gram can be considered to be representative a shallow moist layer (but not necessarily

of the conditions before the squall ; above it, a temperature-inversion) near the surface the tephigram shows conditions during the which v>rill often appear to have considerable occurrence of the duststorm. As the tempera- real latent instability. But here it is well to tures rise in the upper levels after a dust- allow for the effect of convection in lowering storm, the area is greater BCDEB perhaps the surface wet bulb by mixing with the than it would be before the occurrence of the drier layers aloft, for in this way the amount phenomenon ; for the same reason the tem- of latent instability for the surface particles peratures along BF may have been lower can be rapidly decreased before the convection before the squall, making the area AFB reaches the condensation level. The method slightly greater. of assuming an average wet bulb for the The possibility of descending cold air from lowest layers, in the same sense as Mr. a dust- or thunderstorm which occurred at Namias suggests using an average specific neighboring stations having travelled to Agra humidity, is often called for in such situa- and lifted up the "latently unstable" mass of tions. On the other hand, evaporation often air is not entirely ruled out, but in the ab- keeps the surface wet bulb from falling or sence of positive evidence to this effect and even increases it in spite of mixing, and then in view of the fact that the superadiabatic the depth of the moist layer is increased at lapse rate existing is itself sufficient to cause the expense of the drier upper air—which the phenomenon, it seems reasonable to attri- means the latent instability is increasing. bute the duststorm on this day to the trigger Likewise advection of moist or dry currents action of insolation leading to a superadiabatic aloft will alter the state, as explained in the lapse rate. The latent instability in this case article on Isentropic Analysis. Isentropic is apparently built up by the moisture brought cross-sections and charts are not conveniently in by the passage of the low-pressure wave compared with estegrams since the former referred to above in the description of the contain only Q, and q (or condensation pres- synoptic situation of the day. sures). — :

THE TEPHIGRAM 59

responding to the tephigrams were drawn in each case as follows: —the dry adiabatic (isentropic) is draAvn through the point at the surface level, and then the isohygric (constant mixing-ratio line) through the corresponding dew-point is drawn. The saturation adiabatic which runs through their point of intersection meets the isobar at the surface level at a point which has a temperature coordinate of T°A. This is the adiabatic wet-bulb temperature of the air particle at the surface level. The wet- bulb temperatures at the other levels are obtained in the same manner, and then the estegram is drawn by joining all of the points so obtained. Sohoni and Paranjpe found that the absence of latent instability is associated with dry, fine weather with occasional high clouds of non-convectional type, and latent instability with

Fig. 16. Airplane Sounding at Murfreesboro, convectional types of clouds. Later Tenn., plotted on the pseudo-adiabatic chart. studies in India confirm this and the The temperature curve is drawn as a full line with specific humidities written in to its right. wet-bulb curve is now widely used. The wet-bulb curve is drawn as a heavy dashed line with relative humidities entered beside it. It is also practicable to determine the This case is of interest because it shows conditional instability in most layers but without presence of what Rossby calls "con- real-latent or pseudo-latent instability. There vective (or potential) instability" of is a little convective instability aloft (e.g., just above 785 and 630 mb) where the wet a layer of air by use of the wet-bulb bulb lapse rate is greater than the moist adiabat. temperatures on a tephigram (also on Bodily lifting of the surface layers by 100 the pseudo-adiabatic chart). In any mb or more would make some fairly thick Cu clouds whereas considerable solar heating of layer of air in which the lapse rate of the surface layers will produce only Fc or exceeds the Sc, if any clouds at all, (because the con- the wet-bulb temperature densation level will be raised). moist adiabatic rate, the wet-bulb po- The sounding is in general rather stable in spite of moderate to high relative humidities tential temperature, and, therefore, and conditional instability in the lower levels ; temperature this is because there is no latent instability in the equivalent-potential the first km or two. B. G. S. decreases upwards. A layer of this In a study of some Indian tephi- type is convectively unstable according grams, Sohoni and Paranjpe** have to Rossby's definition. If such a layer applied Normand's suggestions and is raised bodily and adiabatically in correlated their findings concerning the atmosphere without mixing with the presence or absence of latent insta- its environment or distortion and in bility in the soundings with air-mass such a way that the difference of pres- type and weather. The estegrams cor- sure between the top and bottom of the layer remains constant, then it can ** Sohoni, v. V. and Paranjpe, M. M. easily he seen that every layer in which Latent instability in the atmosphere revealed by some Indian tephigrams, Mem. India Met. the wet-bulb lapse rate is steeper than Dept., Vol. XXVI, Part VII, 1937, pp. 131- 149. the saturated adiabatic must ulti- 60 AIR MASS ANALYSIS

Tnately become unstable if raised to the gram, or emagram) will certamly condensation level. Since energy is re- appeal to practical meteorologists. quired to raise the layer, however, and Even on the Stiive pseudo-adiabatic the almount which must be supplied for chart the wet-bulb curve will be quali- this purpose may exceed the energy tatively helpful, in case there is in- which can be expected from lifting or sufficient time to plot an energy heating, the energy of convective in- diagram. stability may be unrealizable. The only Bleeker has shown that the adia- important types of convective instabil- batic wet-bulb temperature is not ity are those in which the energy which strictly a conservative element for has to be supplied in order to lift the an evaporation process while the iso- layer to the condensation level is less baric wet-bulb is not conservative for than the amount which will be realized wet or dry adiabatic processes, but for from the resulting instability. Such a estimating instability this makes no gain in energy is most likely to be real- practical difference. Petterssen has ized when the layer of air tinder consi- lately suggested drawing the wet-bulb deration is originally nearly saturated temperature curve on the pseudo- or when latent instability is present adiabatic chart to indicate convective from the start. There may be convective (or potential) instability (see Fig. instability with or without conditional 16). This is a more convenient pro- instability at the start, of course. The cedure than plotting a Rossby dia- use of the wet-bulb curve serves to gram, but the deviation of the wet- classify the convective instability ac- bulb curves from the moist adiabats cording to whether there is latent-, is usually so small that the layers pseudo-, or no conditional-instability with convective instability cannot be present at the same time, and hence read off so accurately as on the the relative probability of its release Rossby diagram, though this is not by any trigger actions that can be serious except in borderline cases foreseen on the weather map. In trop- when the inaccuracy of aerological ical regions and in summer in higher measurements would probably not latitudes this simple method of esti- permit a definite conclusion anyway. mating all types of instability on one —R. G. S. diagram (tephigram, Neuhoff dia-

IX. SYNOPTIC ASPECTS OF THE THUNDERSTORMf

In the preceding article the plot- fication of thunderstorms is based ting of the tephigram and a partial upon the physical factors which pre- interpretation of an individual sound- sumably cause them: ing was outlined. This article will 1. Air-mass thunderstorms: present briefly the probable causes (a) From local convection. In thermodynamically of thunderstorms, indicating the use (6) cold air masses. of aerological data in their analysis 2. Frontal thunderstorms: and forecasting.! However, the origin (a) Associated with a cold and development of the thunderstorm from the sjmoptic viewpoint front. Associated with a warm are by no means fully understood (6) front. as yet, and therefore offer a fertile field for research. tFurther discussion of thunderstorm fore- Perhaps casting will be found in Article X on Isen- the most convenient classi- tropic Analysis. THUNDERSTORMS 61

(c) Associated with an oc- tice to take for the maximum tem- cluded front. perature of the day the surface tem- 3. Orographic thunderstorms. perature which would be potentially 4. Thunderstorms in horizontally equivalent to that at the top of the converging air currents. ground inversion. The physical reas- oning behind this procedure is that as I. Air Mass Thunderstorms insolation warms the ground the A. From local convection. The type stability of the overlying inversion of thunderstorm known for a long precludes any appreciable upward time as "local," "heat," or "local transfer of the heat supplied the convective" may be singled out from surface layer. Consequently, the other types in that it represents a lowest layer warms up rapidly until form of penetrative convection due the ground inversion with its stability primarily to insolational heating in is completely wiped out. After this the lower layers of the atmosphere. takes place most of the excess heat No apparent frontal activity is in- is carried upward by convection, and volved, and the original cause appears the temperature at the surface re- to be purely thermal in nature. In mains at a fairly constant maximum. summer these thunderstorms may be In choosing the specific humidity of observed in almost every type of air the particular element which is to mass. They are, however, by far rise through the surrounding air mass most frequent in Tg air, because the it is customary to assume that the Tg air has the most favorable moist- specific humidity in the surface ure and temperature distribution layers remains constant. This is with elevation. Steep lapse-rate and logical because, exclusive of evapora- high specific humidity are most favor- tion from the surface and mixing with able for the development of Cu clouds the air above, the mass of water into tall Cb. The tephigram under vapor per unit mass of air should such conditions generally exhibits a remain sensibly constant in one and large positive area and a compara- the same air mass; in a case where tively small negative area. As pointed the specific humidity decreases out in the preceding article, it is im- rapidly upward from the surface, the portant to use critical judgment in mixing by convection and mechanical selecting which particle of air will be turbulence will lower the specific hu- assumed to penetrate the upper midity of the surface air. In this strata; furthermore, it is necessary to case it would be erroneous to pre- assume the temperature and moisture sume a constancy of moisture content that particle will probably have be- during the day. In practice I have fore it ascends. Thus if one should found it helpful in these cases to choose the surface air particle having choose for the probable specific hu- the temperature and moisture ob- midity of the rising particle the Tnean served in the early morning hours value of the observed specific humidi- he would, owing to the stability of ties through the lowest layers up to the ground inversion, always obtain the condensation level, or to the top tremendous negative areas. In fore- of any ground inversion or stable casting a maximum temperature for layer having relatively high humidity. the surface particle one should be A not uncommon case presents familiar with the locality for which itself when above the moist surface he is forecasting. It is common prac- air, presumably Tg, there flows a 62 AIR MASS ANALYSIS

current of warm dry air (Ts) ; if the overturning is taking place, because Tg air is shallow, the construction these turbulent ascending bodies may of a tephigram with the assumption be virtual "fountains" of moist air. that the surface particle will pene- Further research is required here. trate the Ts air will often be mis- In making use of the tephigram leading, for it suggests there are in forecasting local thundershowers it large amounts of available energy is important to consider the chrono- {positive area) which actually, how- logical changes in the positive and ever, cannot be realized because of negative areas. Rapidly increasing the mixing of this moist stratum with positive areas and decreasing nega- the dry air above. But generally, tive areas are highly indicative of especially when the Tg air is about future thunderstorm activity. If a 1 km deep, the tephigram gives a succession of six- to twelve-hourly fairly true picture of the available ascents is not available, it is very energy, indicating (after extrapola- helpful to choose for comparison tion of the surface point) positive tephigrams of ascents made the pre- areas at the surface and aloft separ- ceding few days at other stations in ated by a negative area. This stable the same air mass, preferably ones layer (the negative area) tends to lying in the general trajectory of the resist convection and must in some air mass—that is, in the probable manner be penetrated by the rising path of the air current before it particle before the Cu clouds can reached the station for which the develop into thunderstorm propor- meteorologist is forecasting. tions. It is conceivable that in some The local indications of convective cases the extra energy needed to thunderstorms are so commonly overcome stability may be supplied known" that we need not dwell upon by the kinetic energy of the rising air them here in detail; some may be —this energy causes the cloud to rise mentioned: the presence and growth beyond the level at which it has the of towering Cu during the day, the same density as its surroundings. warm, muggy and often stagnant The energy may at times be supplied atmosphere, and the steep pressure by the lifting action of an incoming fall by afternoon. The distribution front or by orographic upthrusting. of the Cu is frequently indicative, for it has been shown by Bjerknes^ that In a special study of aerological tall Cu separated by fairly large clear material Willettf found that the Tg spaces (Cu. castellahis) are most layer, whether or not a front enters the synoptic field, must be at least tDisoussion and Illustration of Problems Sug- gested by Analysis of Atmospheric Cross- some 3 V2 km thick for thunderstorms Sections, M. I. T. and W. H. Ocean. Inst., to develop. As he points out, however, Papers in Phys., Ocean, and Met., Vol. 4, No. 2, 1935. his data contained no ascents made *For further discussion of this see my article during June through September—just in the Jan. 1938, Bulletin Am. Met. Soc p. 11. the time of the year when convective -Cf. C. F. Brooks: The )c«?al, or heat, thunderstorm. Mo. Weather Rev., June, 1922, Vol. activity is greatest. It is the prob- 50, pp. 281-284. (Includes "Questionnaire [of able, then, that this conclusion does 16 questions] for predicting local thunderstorms.") not hold for summer situations.* It ^Pnysikalische Hydrodynamik. Berlin, 1933 ; Hydrodynamique Physique. Paris, 1934 (3 is also likely that soundings in made Vols.). In Q. Jn. Roy. Met. Soc, April 1938, or near a Cb cloud are not repre- pp. 325 ff, Bjerknes shows that Cu convection does not release sufficient kinetic energy sentative of the properties of the (motion) to cause Cu to develope into Cb unless the spacing thickness ratio of the Cu air mass in the convective — which towers is below a certain critical value. THUNDERSTORMS 63

favorable while flat Cu {Cu. humilis) the spring, on the other hand, the covering most of the sky are contra- Pc air may be transported from its indicative of thunderstorm activity. snow-covered source region to the

There is, however, a limit to the nar- warmer bare-land surface in such a rowness of Cu, for tall narrow clouds short time that the upper layers have are apt to be torn apart and dissi- little time to warm, and consequently pated by turbulence and wind shear. very steep lapse-rates are established. Thus there is an optimum size and Another restraining influence on space distribution for Cu in order for the formation of this type of thunder- Cb to develop. storm is the presence of surfaces of Although the following rule is more subsidence within the cold air, which or less obvious, it is important enough act as "lids" that stop the upward to italicize: Before attempting to growth of the Cu clouds in the cold use the indications of a tephi- air; it requires considerable energy gram in forecasting local convective for the rising air to penetrate these showers make certain that no fronts stable surfaces. The limiting sub- will enter the field within the period sidence layers generally lie within the for which you are forecasting. Thus cold air in the shape of a vast, flat the intelligent use of upper air data dome—the top being near the center goes hand in hand with a reliable of maximum pressure rise (anallo- analysis of the synoptic chart. bar) , the edges becoming lower as B. Thunderstorms in thermody- the front boundary of the cold air rroasses. In this namically cold air mass is approached. Consequently, type of thundershower the steep for some distance behind a cold front lapse-rate in the surface layers is conditions are unfavorable for the established chiefly by the transport of type of shower in question, for here over a cold (usually Pc air) current the surface of subsidence is lowest. a relatively warm land surface. The Moreover, near the front the stability Pc air mass is considered cold in a of the frontal (vertical) transition thermodynamic sense, because it re- zone helps to check the convection in the sur- mains continually colder than the cold air. (See Figs. 17 and 18.) face over which it is travelling. Con- It is difficult to apply the tephi- sequently, the lapse-rate in its lowest gram to these situations. One cannot layer must be steep. The situation is make certain of the extent of the characterized in winter by instability warming or humidification of the low- snow flurries, in spring and early est layers of the air mass, or for that summer by instability showers which matter, the changes in structure infrequently develop into thunder- which may go on aloft. A sequence showers, and then usually mild, for of tephigrams constructed from the necessary ingredients of a well flights at fairly short intervals is the developed thunderstorm, air with high most helpful. Lacking these, perhaps moisture and heat content, are lack- the best indications are expressed in ing. the history of the cold air mass traced In summer time this kind of through analysis of the surface thunderstorm is not common, its for- charts. mation apparently being hindered by II. Frontal Thunderstorms the gradual transformation of the Pc properties as the air mass moves A. Associated with a cold front. southward over warmer surfaces. In Cold-front thundershowers are the 64 AIR MASS ANALYSIS most interesting and generally the evening, are characterized by thun- most violent of all. In the older derstorms all along their length.* terminology they are the "line squall" The cold air immediately behind thunderstorms. The predominating the front is cooled by evaporation of cause appears to be the mechanical the falling rain; in this manner the upthrusting of the warm air by the sharpness of the front is maintained. advancing cold wedge. The indica- The air masses preceding the front tions for thundershowers with the on which cold-front thunderstorms passage of a cold front are to be may be observed hardly seem to be found largely in the upper air char- restricted to any individual types, acteristics of the warm air mass and although they occur with a pro- in the structure and movement of nounced maximum frequency in Tg the cold front. The tephigram is currents, and only rarely (if ever) well-adapted to these cases. The in the dry currents which move from soundings used should naturally be the southwestern U. S. and Mexico. those in the warm sector. As before, Cold-front thunderstorms may be a sequence of soundings at one sta- further classified as prefrontal, front- tion is best, but if this is not pos- al and postfrontal, according as they sible it is advisable to study several occur appreciably before, at, or after tephigrams that show the trend of the the front passage. We need spend change in the characteristics of the little time here on the fine points of warm air mass. Here again, increas- this classification. Prefrontal types ing positive areas and decreasing may be due to mechanical uplifting negative areas are most favorable of the warm air some distance ahead indications for thunderstorms, par- of the cold front, or to the entrap- ticularly if the current tephigram ping of the warm, moist air below the shows appreciable positive areas. The overrunning squall head. In the most indicative lapse-rates are con- latter case it is conceivable that ex- ditionally unstable. Convective in- tremely steep lapse-rates and violent stability is also generally indicated, storms may be brought about. Those for it may be that the lifting of entire thunderstorms occurring immediately layers is responsible for the genesis at the front are presumably the nor- of the showers. mal type due to uplifting. The post- In forecasting cold-front thunder- frontal thunderstorm probably be- showers it is important to consider longs, for the most part, to the class the diurnal change in lapse-rate. In discussed as "thunderstorms in the early morning hours there is thermodynamically cold air masses." usually a ground inversion present, An interesting situation occurs while in the afternoon the surface when a cold front slows up in its layers are characterized by a super- movement and becomes quasi-station- adiabatic lapse-rate (Fig. 19). Then ary. Then thunderstorms may be the air mass is in its most favorable occurring at various points along the state for producing thunderstorms once front and persisting for a relatively the "trigger action" of a cold front long time. These are associated with is supplied. It is for this reason that small wave disturbances rhoving cold fronts passing during the night are *This is brought out clearly in the statistical frequently accompanied by no frontal study of Thunderstorms in Ohio during thunderstorms, while the same fronts, 1917, by W. H. Alexander, C. F. Brooks and G. H- Burnham, Mo. Weather Rev., July, 1924, passing during the afternoon or early Vol. 52, pp. 343-348. — —

THUNDERSTORMS 65

along the front and supplying the the lapse-rate in the warm air, for necessary "trigger action" to release the surfaces of equal potential tem- the energy in the warm air. The perature are stretched vertically.'^ showers apparently form both in This process may be considered the advance of and behind the front, but reverse of subsidence, wherein hori- the structure and action of these zontal divergence occurs and the waves is not fully understood. Ex- lapse-rate becomes more stable. With cellent examples of these quasi-sta- horizontal convergence in the warm tionary frontal thunderstorms can be sector, the air involved is so trans- observed in summer over New Eng- formed that the relatively small land. vertical motions supplied by ascent over the cold wedge are sufiicient to B. Thunderstorms associated ivith develop thunderstorms. It is obvious a warm front. Thundershowers as- that this same conditioning process is sociated with a warm front are not also important in setting the stage nearly so common as those with a for other types of thundershowers. cold front, the reason being that the The major action in warm-front vertical motions brought about by a thundershowers takes place aloft. warm-front surface are not as pro- The storms are usually less violent nounced as with a cold front. Never- than other types. Furthermore, the theless, in favorable circumstances characteristic cloud display may be one may observe on the surface obscured by the warm-front cloud weather map the outbreak of a large deck. number of thunderstorms definitely diurnal variation in frequency associated with a warm front. It The of these showers is not as pronounced appears that this type is almost as with the other types, particularly entirely confined to fronts where Tg in the non-summer months, when is concerned, particularly in autumn, to about as frequent winter and spring; there are occa- they seem be at night as by day. sional summer cases, where the warmer air mass is a transitional Just as with quasi-stationary cold polar current whose temperature and fronts, waves may form on a slowly moisture content have been increased moving warm front and may at times by stagnation over the southeastern be responsible for the development U. S. almost to the characteristic of thunderstorms along it. It is not values for tropical air. These warm- rare to find a comparatively sudden sector air masses capable of produc- outbreak of violent showers along an ing warm-front thundershowers are east-west front separating Tg from well supplied with potential energy, Pc air, and usually this can be traced which is on the verge of being re- to some wave action which has released. The releasing agent or leased large amounts of indicated (on "trigger action" necessary for the the tephigram) energy in the To air. transformation of this potential In using the indications of the energy into the kinetic energy of a tephigram for forecasting warm- thunderstorm is the upward deflec- front showers one must locate accu- tion of the warm air over the cold tln India it has been shown that the cold wedge.f air descending out from under one thunderstorm often spreads out along the surface as Another important factor is the a local cold wedge and acts as a trigger to set off new thunderstorms nearby. Ed. horizontal convergence of air in the *This is true only in case the original lapse rate was stable, otherwise convergence would sector; this serves to steepen warm tend to stabilize the air. Ed. 66 AIR MASS ANALYSIS rately the position of the warm front be treated in the same manner as at the surface, and obtain a fairly cold fronts. good idea of its structure. A sound- The occluded warm front is inter- ing made some distance in advance of esting in that it represents an upper a warm front, if subjected to the cold front marching into the field ordinary analysis for local con- aloft, well in advance of the surface vective showers, will rarely show warm front; the warm air originally thunderstorm indications, because above the warm front surface is thus here the erroneous assumption is displaced by a current of colder air. made that the surface cold air, in In this way, the lapse-rate above the reality belonging to the cold wedge, lowest part of the warm front is will rise through the upper strata. made steeper. These warm-front oc- The proper procedure in these cases clusions seem to be characteristic is first to identify the discontinuity over the southwestern plains, where surface separating the two air masses the Tg air is colder than other warm aloft, then instead of a surface parti- air masses (often Ntp) which there- cle assumed to rise take some element fore override it, while Npp air, in the warm sector, ascribing to it a warmer at the surface than the Tg, probable maximum temperature as in but colder than the Ntp, rapidly over- the case of air-mass ' convective runs the Tg and displaces the Ntp; showers, and then plot the ascent of the warmest air is then pocketed be- this element on the original tephi- tween the Tg wedge and the Npp. gram. It is best to choose for the wedge." Thunderstorms are at times rising particle the air at the base associated with this structure, though of the warm current. their exact mode of formation is C. Thunderstorms associated with not as yet definitely known; but it an occluded front. Perhaps the larg- appears that the steep lapse-rates est number of summer thunderstorms observed aloft in the Npp air mass are associated with fronts previously play an important part once some occluded, which, through their action particular body of air starts to rise. on the field of flow, have regenerated It is possible that insolational heat- into active cold fronts. It is im- ing in the cool wedge (Tg) may portant in summer for the analyst give the initial impulse, while the to follow closely all occluded fronts, stability of the frontal boundary may for it is the rule rather than the be insufficient to prevent its penetra- exception for bent-back occlusions, tion into the more unstable air aloft. weak as they may appear, to develop In making use of the tephigram in into surprisingly active cold fronts. these situations one must consider the It is largely the activity of these possibility of rapid change in struc- occlusions that makes summer-map ture of the upper air and must be analysis so interesting. They form, familiar with the characteristics of all as do ordinary cold fronts, a the interacting air masses. convergence, pronounced field of III. Orographic Thunderstorms making the front sharper and con- Practically all types of thunder- ditioning the preceding warm air to storms are more frequent over hilly the point where it becomes rich in and particularly over mountainous convective energy. In general, for

: of Warm-front- purposes of thunderstorm forecast- ^Cf . H. Wexler Analysis a type Occlusion, Mo. Wea. Rev., July, 1935, ing, these cold-front occlusions may pp. 213-221. THUNDERSTORMS 67

country than over flat terrain. Be- lapse-rate steeper. This process is sides there are many situations in undoubtedly present in most open which thunderstorms form only in warm sectors. There are many cases that part of an air mass overlying in which a bent-back occlusion in certain mountain regions. The reason some manner establishes behind it a for this seems to be that rough ter- strong convergent field, so that the rain increases vertical turbulence, and front appears to be elongating itself. slopes force marked ascent of the air. In the U. S. this convergent zone is These upward deflections may be generally accompanied not only by enough to set free any large stores an abrupt wind-shift, but also by of energy available in the air masses typical cold-front characteristics; and (especially the conditionally un- there presumably are case^ of such stable). Solar radiation on moun- zones of convergence in which there tains is more intense, and it is also is a pronounced wind-shift but no conceivable that the higher angles of discontinuity in temperature. Such incidence of the solar rays on some a zone cannot be called a front. mountain slopes may favor convec- The Norwegian meteorologists have tive thundershowers. found several cases of this kind over A characteristic of many of these Europe.^ The characteristics of such a trough of showers in mountainous regions is low pressure are similar their tendency to remain almost sta- to a front. Owing to the converg- tionary, presumably because the up- ence there is frequently precipita- ward deflection of the air flow over tion. As far as I am aware, no one the mountain is operative in only has published an analysis of such a certain localities (windward sides) case in the U. S. It seems probable while dissipating forces are at work that bent-back occlusions here almost in others (leeward). invariably regenerate into cold fronts, because the air masses concerned Another type of orographic thun- (iisually Pc or Npp) seem to undergo derstorm is the coastal shower in modification along their trajectory conditionally unstable maritime air more rapidly than the air masses over masses, frequent on the Pacific north- Europe (moist maritime-polar cur- west coast of the U. S., where the rents) (see Petterssen: Contribution ascent of fresh Pp air up the coastal to the theory of Frontogenesis). slope and ranges supplies the "trigger action." A similar phenomenon Another type of convergence, which might occurs in conditionally unstable (or have been discussed under the convectively unstable) Tg air masses heading of occlusions, is that forcibly invading the country along the Gulf brought about by the rapid occlusion coast, where the slight elevation of of a cyclone at its center. This the land and initial heating over land occlusion may eventually lead to appears to be sufficient to produce thunderstorms but only when the cold showers. front rapidly cuts off the warm sector and the warm air is not very stable. IV. Thunderstorms in Horizon- This kind of thundershower is often tally Converging Air Currents observed over southern New Eng-

It has been pointed out that hori- °J. Bjerknes : Investigations of Selected Eu- zontal convergence of air, through its ropean Cyclones by Means of Serial Ascents (Case 3: Dec. 30-31, 1930), Geofysiske Puh-, vertical spreading action, makes the likasjoner. Vol. XI, No. 4, 1935 (2:00 Kr.). 68 AIR MASS ANALYSIS

land, the winter thunderstorms of thundershowers along the coast. In that section being almost entirely of the warm months of the year the this type; rapidly intensifying cy- effect of the colder water tends to clones (often secondaries) bring a retard the warm front, while the cold tongue of Tm air to their centers front proceeds to occlude the warm where it is rapidly occluded, causing sector.

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72 AIR MASS ANALYSIS

The Ice-Nuclei Theory of Rainfall

When a cloud top grows a consider- high latitudes, but is not yet accepted able distance into region above the as universally true, as there is much 0°C level, more and more ice crystals evidence from the tropics and sub- will form, creating a layer of water tropics that certainly it is not always applicable there. and ice particles and perhaps still higher one with ice crystals only. If and where the principle holds, Bergeron developed a theory (later however, then the most favorable con- elaborated by Findeisen) that large- ditions for the development of thun- exist dropped rain will not be precipitated in derstorms would when the dis- considerable amounts until the top of tance between the lowest level where convective energy would freed and the cloud is partly composed of ice be crystals, because the difference in the ice-crystal level is great and the vapor pressure over ice and water amount of latent energy is large. Un- leads to rapid growth of the ice der such conditions the rising particles crystals by evaporation from the of air would have sufficient energy to drops, the ice crystals then falling out, reach well above the ice-crystal level, melting and taking on more water on and at the same time the lower air the way down as rain. Other clouds are particles would be accelerated up- more colloidally stable and give only ward for a long time, leading to high fog or drizzle. This theory seems to velocities and release a maximum of agree with observations in middle and heat from condensation. R. G. S.

Hail Forecasting

A recent study made by United Air deficiency is eliminated. The follow- Lines meteorologists indicates that in ing empirical results from the study, the central and eastern United States, however, have a certain forecasting large hail falls mostly in showers oc- value: curring between noon and 9:00 P.M. No falls of lai-ge-hail were reported and especially between 3:00 and 6:00 in thunderstorms which occurred when the base of the conditional or P.M. Over half the hail falls were convective instability region was due to frontal activity, but insola- above 7,000 feet. (This region began tional heating during the day ap- anywhere between 3,000 and 14,000 parently intensified the frontal "trig- feet for hailless thunderstorms, but between 3,000 and 7,000 feet for ger action" to a great extent. The storms with large hail.) adiabatic charts and Rossby diagrams The proportion of thunderstorms for hail days were studied but did not producing large hail was one per 400 give very definite criteria for fore- when the lapse rate (°F per 1,000 ft) was greater than 4.5 °F in the con- casting these hail storms. This was vective or conditional instability re- most likely due to the fact that the gion as indicated by the nearest airplane soundings analyzed did not sounding. The frequency was only one-third this great (one in reach over 15,000 or 17,000 feet, and storm 1,200) when this lapse rate was positive at those elevations the energy smaller than 4.5 °F and the base of areas were usually either at their the instability level still below 7,000 maximum width or still wide open, so ft. The lapse rate referred to was generally between 3.5° and 4.5 °F for that the real extent of the energy non-hail storms, but anything between areas could not be taken into account. 3.5° and 5.5° for storms with large With the radiosondes now used this hail. —

CHARACTERISTIC AIR MASS PROPERTIES 73

Characteristic Properties of North American Air Masses^

H. C. WiLLETT U. S. Weather Bureau, Boston, Mass. Associate Professor of Meteorology, Massachusetts Institute of Technology Lecturer in Meteorology, Harvard University

I. INTRODUCTION In this discussion the term air mass of the mass However, the horizontal is applied to an extensive portion of differences produced within an air the earth's atmosphere which approxi- mass in this manner are small and mates horizontal homogeneity. The continuous in comparison to the formation of an air mass in this sense abrupt and discontinuous transition takes place on the earth's surface zones, or fronts, which mark the wherever the atmosphere remains at boundaries between different air rest over an extensive area of uni- masses. Frontal discontinuities are form surface properties for a suffi- intensified wherever there is found in ciently long time so that the proper- the atmosphere a convergent move- ties of the atmosphere (vertical dis- ment of air masses of different prop- tribution of temperature and moist- erties. ure) reach approximate equilibrium Since the air masses from partic- with respect to the surface beneath. ular sources are found to possess, at Such a region on the earth's surface any season, certain characteristic is referred to as a source region of properties which undergo rather defi- air masses. As examples of source nite modification, depending upon the regions we might cite the uniformly trajectory of the air mass after leav- snow and ice covered northern por- ing its source region, the investigation of the continent of North Amer- tion of the characteristic properties ica in winter, or the uniformly warm of the principal air mass types can waters of the Gulf of Mexico and the be of great assistance to the synoptic Caribbean Sea. meteorologist and forecaster. We The concept of the air mass is of owe this modern analytical method of importance not in the source regions attack on the problems of synoptic alone. Sooner or later a general meteorology and weather forecasting movement of the air mass from the to the Norwegian School of Meteor- source region is certain to occur, as ologists, notably to J. Bjerknes and one of the large-scale air currents T. Bergeron. The analytical study which we find continually moving of the synoptic weather map is based across the synoptic charts. Because 'An abstract and revision of American Air of the great extent of such currents Mass Properties, Papers in Physical Oceano- graphy and Meteorology, published by Massa- and the conservatism of the air mass chusetts Institute of Technology and Woods properties, it is usually easy to trace Hole Oceanographic Institution, Vol. 2, No. 2, 1933 (now out of print). A part appeared in the movement of the air mass from the Jn. Aeronaut. Sci., Vol. 1, No. 2, April, day to day, while at the same time 1934, pp. 78-87. The revisions herein concern chiefly the Tropical air masses ; but it should any modification of its properties by be understood that this discussion of the the new environment can specific properties of the American air masses be carefully was a preliminary and pioneer work and the noted. results have required some modification as further accumulations of aerological data and ex- Since this modification is not likely perience have been studied. A later study to be uniform throughout the entire by Showalter is abstracted at the end of this article (pp. 109-113). The Bibliography lists air mass, it may to a certain degree many later papers which should be consulted by the serious student, as great advances are destroy the horizontal homogeneity being made yearly. Ed. 74 CLASSIFICATION OF AIR MASSES

essentially on the identification and tribution) be approximately known. determination of the movement of air This is especially true of aviation masses and fronts rather than of forecasts, for just the meteorological areas of high and low pressure as the elements which are of greatest in- entities of prime significance. The terests to the pilot are those which justification of this procedure is evi- are dependent upon the air mass dent from the fact that the weather properties. For good forecasting of which is experienced in a given region convective turbulence, thunderstorms, does not depend upon the prevalence horizontal visibility, fog and haze, of high or low barometric pressure. cloud forms and ceiling, for just such Even in the same locality a high or a forecasting full knowledge of the air low may be accompanied by widely mass properties is essential. Since it varying meteorological conditions. rarely happens that the forecaster The weather in a given locality de- has available for the current weather pends upon the properties of the air map aerological material sufficient for mass which is present or upon the the satisfactory determination of the interaction which is taking place be- properties of the air masses present, tween two air masses along a front an investigation of the characteristic in the near vicinity. The funda- properties of the typical American air mental concept is that of the air masses should be of value both for mass, for upon the properties and practical weather forecasting and for movements of the individual air a better understanding of the physi- masses appearing on the map depend cal processes underlying our usual not only the weather in the area weather sequences. It was with this covered by each air mass but also thought in mind that the paper here the formation and intensification of under consideration was written. The fronts and the genesis, development discussion was definitely restricted to and movement of lows or disturb- a consideration of the homogeneous ances on the fronts. But in order air masses individually, the investiga- that the full advantage of a careful tion of the whole complicated frontal analysis of the weather map may be problem of converging air masses utilized in weather forecasting, it is absolutely necessary that the thermo- being left for later consideration in dynamic properties of the air masses the light of more extensive American (lapse-rate and vertical moisture dis- aerological data (see Bibliography).

11. CLASSIFICATION OF AIR MASSES

The study of synoptic weather observation, any classification of air maps indicates that air masses are mass types must be based funda- entities having such definite charac- mentally on the air mass source teristic properties that they may be regions, with perhaps a sub-classifica- classified and studied as distinct tion based on later modifications of types. Since the characteristic prop- the source properties. erties of an air mass at any point The air mass sources fall naturally depend primarily upon the nature of into two groups, the tropical or sub- its source region and secondarily tropical, and the polar or sub-polar. upon the modifications of the source The large areas on the earth of uni- properties which the air mass has form surface conditions and compar- undergone en route to the point of atively light atmospheric movement CLASSIFICATION OF AIR MASSES 75

lie almost entirely at high latitudes necessary to keep in mind the season or at low latitudes. In middle lati- of the year when considering the tudes, generally speaking, we find the characteristics of any particular geo- zone of greatest atmospheric circula- graphical source region, as these char- tion or of most intense interaction acteristics, especially in the case of between the warm and cold currents, the continental areas, change greatly i.e., air masses from the tropical and from the cold to the warm season. polar regions. Consequently, in It is also necessary to consider the middle latitudes the uniformity of modifications of the original source conditions and the light air move- properties of the air mass types, ment which must characterize a effects which become more pro- source region are generally lacking. nounced with the increasing move- Rather than the development of hori- ment of the air mass from the source zontally homogeneous air masses, we region. Eventually the properties of find here the rapid modification, in the air mass become so fundamentally varied forms, with changing environ- modified from the source properties ment, of the characteristic polar and that the mass must be given a special tropical air mass types. Thus the transitional designation. basis of any comprehensive air mass Table II gives the complete classi- classification must be the distinction fication of the principal North Ameri- between the polar and the tropical can air masses by geographical source source types, with a further distinc- regions, together with the principal tion between the modified forms transitional form for each air mass. which these principal types acquire The ordinary designation and the in middle latitudes during their later symbol entered for each air mass in life history. the last two columns are those which The air mass classification may be appear on the Massachusetts Institute carried further by the sub-division of of Technology weather maps. the polar and the tropical source It is with the purpose of making types into continental and maritime this discussion intelligible to meteo- groups, according as the source in rologists who are not familiar with each case is a continental or an our local classification, and of making oceanic region. Since the uniform the American air mass data more di- source regions are always entirely rectly comparable with the European continental or entirely maritime and data, that the general air mass classi- since this is the essential difference fication outlined by Bergeron is also between source regions in the same introduced in this paper. latitude, this distinction furnishes In the general air mass classifica- a satisfactory basis for a general tion which Bergeron^ has suggested grouping of the air masses from each for climatological and comparative latitudinal zone. Consequently, for purposes, and which, at least in its the investigation of the properties of broader features, Moese^ and Schinze^ the air masses which may appear in

-T. Bergeron : Rechtlinien einer dynam- a given locality, the most significant ischen Klimatologie, Met. Zeit, 1930, pp. designation of the different individual 246-62. =0. Moess und G. Schinge : Zur Analyse von polar and tropical air mass types is Neubildungen, Ann. d. Hyd., March, 1929, pp. 76-81. that based on the particular geo- *G. Schinze : Tropospharischen Luftmassen graphical area within which the air und vertikaler Temperaturgradient, Beitr. z. Phxjs. d. fr. Atmos., Bd. 19, 1932, pp. 79-90; mass has its source. It is, of course, see also Met. Zeit., May 1932, pp. 169-79. 76 CLASSIFICATION OF AIR MASSES

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CLASSIFICATION OF AIR MASSES 77 follow in their discussions of Euro- the air mass moves over a surface pean air masses, the essential dis- colder than its own temperature at tinction is still that between the tropi- the ground, the tendency is towards a cal or the polar source of each air cooling of the lower strata of the air mass. However, Bergeron carries this mass, i.e., an increasing thermal sta- zonal distinction one step further, dis- bility, and towards a decreasing mois- tinguishing between real Arctic (A) ture content of the mass, caused by and sub-Arctic, or Polar (P) air mass condensation from the cooled air sources in the north, and between strata. Evidently Polar air masses sub-Tropical (T) and real Equatorial must normally undergo the first type (E) or Trade wind zone air mass of change when modified after leaving sources in the south. Bergeron points the source region, and Tropical air out, however, that in northwestern masses the second type. However, Europe the Equatorial air masses there may be exceptions in both cases, play a negligible role, appearing only and any air mass may for a time be at high levels in the atmosphere, if at subjected first to the one and after- all. In the case of the North Ameri- wards to the other type of influence. can air masses the distinction between In Bergeron's general air mass Polar and Arctic air masses and that classification, modification of the between Tropical and Equatorial air source properties of the air mass, masses are both dilBcult to make and which in the local classification is in- of little significance. dicated by the N (transitional) The principal source air masses in group, is indicated by a W (warm) or Bergeron's classification are the conti- a K (cold, kalt) distinction according nental Arctic (cA), maritime Arctic as the recent modification of the air (mA), continental Polar (cP), and so mass has been of the second or the on through the MP, cT, mT, cE and first type mentioned above. The warm mE groups.* Of course such a designa- (W) designation indicates that the tion of air masses, while indicating air mass is warm relative to the sur- very definitely the type of each air face it is m-oving over, the cold (K) mass, is of necessity less precise in designation indicates that it is cold the information it gives to one tho- relative to the surface it is moving roughly familiar with the particular over. Thus in the general classifica- sources in question than is the local tion of air masses the source designa- classification by direct specification of tions cP, mP, cT, and so forth, when the source of each individual air mass. applied to air masses which have left Air masses of Tropical and Polar their source regions, appear in the origin are modified during their later modified forms cPW (continental Po- history in either of two essentially dif- lar Warm), cPK (continental Polar ferent ways. If the air mass moves Cold), mPW (maritime Polar Warm) over a surface warmer than its own and so forth, depending upon the type temperature at the ground, the ten- of modification which the air mass has dency is then towards a warming of undergone during its recent history. the lower strata of the air mass, i.e., It should be stressed that this warm an increasing thermal instability, and and cold designation has nothing to do towards an increasing moisture con- with the evidence by the air mass of tent of the lower strata of the air *This manner of designation was introduced mass, caused by evaporation from the into the practice of the U. S. Weather Bureau

•In 1939 ; it has been in extensive use abroad warm surface. If, on the other hand, and become understood internationally. Ed. 78 AIR MASS ANALYSIS a high or a low temperature, but only the disturbing effect on the air mass as to the evidence of a temperature properties of the surface over which near the ground higher or lower than the mass is moving and the consequent that of the surface beneath. This formation of a ground layer with its warm and cold distinction is not al- own peculiar properties cannot be ways easy to make, as the passage of overlooked. When this influence is the air mass from ocean to continent regular and continuous, it gradually or the transition from day to night affects the entire mass until it be- may reverse the sign of the difference comes characteristic for the proper- of the air temperature from that of ties of the mass. On just such influ- the surface beneath. In the present ences depend the thermodynamic discussion the policy will be to consi- "warm" and "cold" classification of air der only the general tendency in the masses already mentioned. But mech- change of properties from one day to anical turbulence produced by surface the next in the history of the air mass irregularities, and the radiational ef- when determining the warm or cold fects of a single night and insolational designation. Continued or increasing heating of a single day often produce surface stability from day to day in- ground layers with properties which dicates a warm air mass (W), con- may be neither permanent nor char- tinued or increasing instability from acteristic of the air mass, and which day to day a cold air mass (K). This consequently must be allowed for in thermodynamic classification of air the discussion of the air mass proper- masses into warm and cold groups is ties in particular cases. Especially essentially differential in nature, de- troublesome are the large radiational- pending as it does upon changes pro- insolational effects at the surface in duced in the air mass properties by dry continental air masses during the Ijoundary surface-temperature differ- warm season. In the central U. S. ences. In contrast to the significance this diurnal surface temperature of the source classification which de- change may amount to more than pends upon the conservatism of cer- 20C°, may produce an afternoon un- tain of the air mass properties, the stable layer more than 2 km thick, and significance of the W and K classifi- may change the air mass from the cation lies in the modification of the warm to the cold type. Fohn and sub- non-conservative air mass properties. sidence effects are also frequently to There are a number of conditions be noted, but they are usually defi- w^hich are more or less frequently met nitely characteristic of certain air v^rith in the synoptic study of air masses under certain conditions, and masses which may locally or tempo- belong as such to the characteristic rarily render difficult the proper class- air mass properties, not being to any ification of an air mass. In particular great extent diurnally variable.

Ill SIGNIFICANCE OF THE PROPERTIES OF THE PRINCIPAL AIR MASS TYPES IN WINTER in determining It is impossible in a short review which are dominant to attempt a full summary of the our winter weather in the United seasonal properties of all of the air States. It is during the winter season masses listed in Table II. Conse- that the air mass contrasts become quently, this discussion will emphasize most significant. The following dis- applicability the air mass types, Pc, Pp, and Tg, cussion will illustrate the —

WINTER AIR MASSES 79

the analytical method to weather tends to effect isothermalcy of , of E forecasting, without pretending to in- whereas a rapid vertical change in dicate more than a small fraction of possibilities with in actual the met indicates marked atmospheric stratifi- practice. cation. If increases with elevation, In Table III we find tabulated for E convection each of the three principal air masses the possibility of thermal ex- at two different aerological stations in the atmosphere is practically with the mean values of the temperature, cluded, whereas if decreases T, the specific humidity,* w, the elevation, the atmosphere is poten- relative humidity, R.H., and the tially unstable, an instability which

equivalent-potential temperature, , becomes actual with sufficient vertical of the affected stratum. at the ground and at the successive displacement is displacement which may km levels above sea level. These mean Such the values are simply the averages of occur at a warm front. The amount effect a numj)er of ascents chosen as typical of displacement necessary to instability of the affected of each air mass type at each station. actual They represented the best observa- stratum is less, the higher its relative tional evaluation which could be made humidity. Table III the first station in- of the so-called characteristic prop- In for each air mass type is the erties of each air mass type at the cluded gives the best indication of time this study was undertaken. one which characteristic properties of the [Since then a further analysis by the directly, fresh Mr. Showalter of the 1935-36 aero- air mass as it advances region. The second logical material has been published from the source to indicate the most {_Mon. Wea. Rev., July 1939) which de- station is chosen form in which the erves careful study. At the end of this important modified appears during its later his- article some excerpts from his paper air mass Ellen- are reprinted, but the original gives a tory. Thus for the Pc air mass, the characteristic cold series of tables and cross-sect.ons of dale indicates middle west, while mean values and frequency diagrams wave type in the the rather funda- for each air mass, which show that Boston indicates mentally modified cold wave type in there is generally a large variation United States. For from case to case of the same air mass the northeastern Seattle indicates the type even in the same season, so that the Pp air mass, mean values must not be accepted characteristic properties as the air approaches the northwest coast too literally. They do not necessarily mass fresh from the give a typical picture because so many of the United States Ellendale indicates the features which probably never all source, while which the occur in any one sounding are averaged importantly modified form the time it together. But the average picture is air mass assumes by necessary and valuable as an orienta- *The quantity w is not quite the specific tion for the student, forecaster, and humidity, defined by Q=0.622e/j3 but the mass water vapor to dry air, defined ap- researcher. ratio of R. G. S.'] proximately by u;=0.622e/(p—e) where e An explanation of the full signifi- and p are water vapor and total atmospheric pressures. (See, Namias, article III.). cance of $ cannot be made here^ but it Ap- E =See C.-G. Rossby : Thermodynamics nlied to Air Mass Analysis, M. /. T. Meteoro- may be stated in a general way that logical Pavers, Vol. 1, No. 3; also Articles III and IV of Mr. Namias' series, in this turbulent mixing of an air stratum booklet. 80 CHARACTERISTIC AIR MASS PROPERTIES —

POLAR CANADIAN AIR—WINTER 81 reaches the interior of the continent, [For a critique indicating some the characteristic Npp air mass type, limitations involved in analyzing the finally, for the Tg air mass, Groes- properties and movements of air beck indicates the characteristic prop- masses solely by comparison of the T, erties as the air mass first advances q, and ^e values at standard elevations northward from the Gulf of Mexico, in the free air as done here, see the while Boston indicates the modified paper by Prof. Rossby in Bull. Amer. form which the air mass assumes as Met Soc, June-July, 1937, pp. 201-9. it moves northeastward, approximat- Isentropic analysis was developed to ing the characteristic Ntm (Ntg) avoid these limitations (see article X type. in this booklet). Ed.'\

IV. WINTER AIR MASS PROPERTIES

Ths Pc Air Masses. Let US con- mechanical turbulence. Consequently sider now the significance of the char- a minimum temperature is often acteristic properties of each of the found just below the 1 km level, with air mass types tabulated in Tables a marked inversion above. In the III-V, bearing in mind that the entire later stages of the cold air outbreak, discussion applies essentially only to as the wind diminishes and becomes the winter months. The Pc air masses very light at the ground, radiational are those which originate over the cooling effects a lowering of the air snow and ice covered regions extend- temperature at the ground, while sub- ing from the interior of Canada sidence effects a raising of the tem- northwestward over Alaska and perature at upper levels.* Thus, with northward into the Arctic. The pass- the possible exception of a shallow age of an air mass of this type over turbulence layer near the ground, the Ellendale marks the advance of the Pc air mass shows very marked stab- typical cold wave from the Canadian ility through the lower 2 km, usually northwest, the characteristic proper- even a rather large temperature in- ties of the air mass observed at Ellen- version, which tends to increase with dale being practically those acquired the aging of the air mass over the in the source region. We note at once Plains states and the Mississippi Val- from Table III the extreme coldness ley, at least as long as the mass of this air mass at Ellendale but also remains over a snow or ice-covered the fact that the temperature in- surface. Passage of the Pc air mass creases above the ground, reaching a during its progress southward over maximum at about the 2l^ km level. bare ground or especially over open Actually we find that in the early water, leads to a rapid heating and stages of the cold air outbreak when moistening of the lower strata. Con- the wind is still moderate to fresh sequently the typical Npc air mass in northwest or north from the ground more southerly latitudes is likely to up to high levels, the temperature be characterized by rapidly diminish- decreases through the first few hun- ing stability, but during the winter dred meters above the ground. This

*See J. Namias : Subsidence in the At- is a result the of mixing affected by mosphere, Harvard Met. Studies No. 2, 1934. «2 CHARACTERISTIC AIR MASS PROPERTIES

season it never becomes really un- tion forms are characteristically stable in the Mississippi Valley before absent, though at the beginning of it reaches the Gulf of Mexico. a Pc outbreak a low stratus or strato- We notice from Table III that the cumulus cloud deck may mark the top specific humidity at Ellendale is very of the turbulence layer, but is likely low at all levels but with a pro- to dissolve rapidly. Otherwise the nounced maximum at the 2 km level, air mass should be cloudless, high whereas the relative humidity is uni- clouds indicating the presence of formly rather high at lower levels. another air mass aloft. Occasionally The indication is that the radiational the radiational cooling of the lower cooling of the surface air strata to strata of the air mass leads to the very low temperatures has led to local formation of frost smoke or ice condensation and deposit of moisture crystal fog at very low temperatures. from these strata. Generally speak- The intensification and lowering of ing, values of specific humidity less the subsidence inversion and the dis- than 1 g and a rapid increase of appearance of all surface wind in with elevation, are characteristic of the stagnant and aging Pc air mass the Pc air masses. favors the accumulation of smoke and A Rossby diagram for Pc air (cPW) dust pollution in the lower levels of at Ellendale shows the typical extrem- the atmosphere. Consequently the history, ely characteristic form of the 8-w Pc air mass during its later especially in industrial regions, curve for this type of air at its source. and is likely to be marked by unusually And this type form is characteristi- the inver- cally conservative at least as long as dense smoke haze below sion sharply marked haze the air mass remains over a snow- and by layers. But the air mass in the covered surface. The curve is nearly central United States is usually too vertical, showing a small increase of dry for the formation of any ex- w at intermediate levels, but with w tensive dense fog below the sub- values less than a gram at all levels. sidence inversion. Fog is likely to The potential and equivalent-potential appear in the old Pc air mass first temperatiires increase some 40 C° in upon the approach of a warm front 4 km; consequently the existence of lowering warm front cloud any mechanically produced turbulence with a deck and precipitation. This is a very effects rapid transfer of heat down- dangerous condition for flying, as it ward in the turbulent layer. favors not only fog formation but The normal flying conditions pre- also heavy ice formation on the plane. vailing in the Pc air mass in winter However, this condition pertains in the northwestern and central essentially to the warm front zone United States may be readily sur- not to the Pc air mass as such. mised from the air mass properties. and In the northeastern United States, The condition will be one of extreme and generally along the Atlantic sea- cold at the ground, but the tempera- board, the Pc air mass properties ture will be much higher at inter- vary significantly from the charac- mediate levels (1 to 2 km above teristics which they show in the Mis- ground) . Bumpiness will be mark- "Valley and the northwest. edly absent, flying being unusually sissippi probably to be attributed to smooth, except perhaps for the shal- This is low turbulence layer near the ground the following facts: when the winds are fresh. Condensa- (1) The existence of considerable POLAR PACIFIC AIR—WINTER 83 areas of open water in the Great ture in contrast to that at Ellendale, Lakes in winter. The rapid heating and the steep turbulence lapse-rate in and moistening which this effects in the first km and the moderate rate the lower strata of the cold, dry, above, such that at the 3 and 4 km stable Pc air masses are evidenced by levels the characteristic Pc tempera- the persistent low cloudiness, con- tures are notably colder at Boston vectional snow flurries and relative than at Ellendale. We observe also warmth of the onshore Pc current the low surface relative humidity which has crossed any of the lakes. increasing with elevation and the Presumably this instability becomes almost constant value of 0E in the rapidly less at upper levels. first km, both of which indicate (2) The presence of the highlands thorough turbulent mixing, while and numerous ridges of the Appa- even at higher levels i^K increases lachians which must be crossed in the much more slowly than in the Pc eastward advance of the Pc current. air at Ellendale. On the western slopes of the Ap- These characteristics of the Pc air palachians the effect of the forced mass in the northeastern United ascent of the Pc current which has States and along the Atlantic coast already been rendered conditionally explain the typical flying conditions unstable over the Great Lakes is to which are met with during its preva- cause general cloudiness and more lence in this region. As long as the or less continuous snow flurries as cold air flow continues actively, the long as the cold air flow continues roughest and gustiest flying condi- unabated. On the coastal slopes the tions which may be experienced in fohn action causes a partial or total winter are to be expected up to dissipation of the cloud deck and considerable elevations. Along the snow flurries. However, the rough Atlantic seaboard the skies are likely terrain maintains a steep lapse-rate to be almost clear, with excellent through the lower km or more, with visibility and, normally, only scat- low relative humidity and relatively tered fracto-cumulus or cumulus high temperature at the ground. clouds, though scattered light snow (3) The increasing depth and flurries sometimes occur in the after- strength of the Pc outflow in the noon. In the Appalachians and on eastern United States. The rapid in- their western slopes one may expect tensification and increasing vertical a rather low broken cloud deck, often depth characteristic of cyclonic discontinuous over considerable areas, turbances moving northeastward over with frequent, extensive and often the United States causes an accelera- heavy snow squalls. After the force tion of the Pc outflow over the east- of the Pc outbreak has been spent, ern United States especially at higher so that the air mass becomes rela- levels. This helps to increase the tively stagnant, then subsidence, radi- turbulence in this air flow at low ation and the cessation of the tur- levels, while the rapid transport bulent mixing all act to establish southward of air from Arctic sources quickly in the Pc air mass the low at upper levels maintains a good inversion, thermal stability and dense lapse-rate aloft. stratified smoke haze so characteristic These effects are to be seen clearly of this air mass in the middle west. in the data for Boston in Table III. Of course, this change is accom- We note the high surface tempera- panied by the complete disappearance 84 CHARACTERISTIC AIR MASS PROPERTIES

of the instability snow flurries, cloudi- precipitation extending far back oi ness, and gustiness. the cold front. As J. Bjerknes" has There is nothing very distinctive pointed out, this type of overrunning about the synoptic situation which is to be expected only when the warm leads to the outflow southward of Pc current is unstable; but as we shall air from the source region in North see presently, marked conditional in- America. Usually the outbreak is pre- stability is always characteristic of ceded by a gradual building up of our Tropical air from the Gulf. Refs- high pressure and low temperatures dal' was the first to call attention to in the source region, often without the importance of the role which con- any very obvious atmospheric move- ditional instability in the atmosphere ments. Sometimes the cold air out- may play in the development of frontal break follows quickly on the first ap- disturbances and in the regeneration pearance of the cold anticyclonic cir- of old occluded disturbances. The culation in the north, but often there writer is inclined to the belief that the is an extended delay, during which moist-conditional instability (Feucht- cold air surges in the north seem on labilitat) of our Tg air masses is a the point of breaking out, only to very important factor in the control recede again. Sometimes the final out- of the interaction between the warm break follows on the passage inland and cold air mass and the stability or from the Pacific Ocean of a disturb- the tendency to occlusion shown by ance usually already occluded in the wave disturbances on the cold front Aleutian Island region. Other times between such air masses. An excel- the cold air suddenly advances with- lent instance of the weather sequence out any very obvious disturbance to with the gradual advance of a cold start it moving. Usually, however, front followed by an extensive Pc air when this happens, one or more dis- mass may be found on the weather turbances are likely to form along the maps and upper-air data for Jan. 13- cold front as it advances southward. 16, 1930 in the U. S. Following the first This is especially likely to happen as sweep of the cold air southeastward the cold air pushes southward to a to the Gulf of Mexico, the whole point where it begins to come in con- frontal system followed by the Pc tact with warm moist air from the outflow advances steadily eastward un- south, particularly Tm air from the til the whole eastern and central U. S. Gulf (Tg). The disturbances usually is covered by the cold air. On the appear first as flat wave formations other hand, it sometimes happens that on the cold front, but are likely to de- the cold air outflow from the source velop rapidly into intense occluding cy- region takes place in one sudden ab- clones which greatly accelerate the rupt outbreak, without the develop- movement of the Pc air behind them to ment of any well-marked disturbance. more southerly latitudes. In such a In this case the cold air sweeps every- development the advance of the Pc thing before it, apparently too rapidly air mass and cold front is likely to be for any localized disturbance to de- checked at first by the warm air cur- velop on the cold front. Furthermore, rent. Then very quickly an extensive these very fast moving cold air out- overrunning of the Pc air by the Tg flows usually occur only on the heels current takes place. The overrunning ^Exploration de quelques perturbations at- circulation tends to develop cyclonically IX, mospheriques. . . . Geofys. Publ., Vol. or counter clockwise, with heaviest No. 9. POLAR AIR MASSES WINTER 85 of a preceding outbreak v/hich has as Gulf of Mexico, the modifications of it were paved the way for it by dis- its properties depend principally upon placing the warm maritime air masses, the extent of the snow cover, for on so that we find the fresh Pc mass dis- this depends the effectiveness of the placing only moderately cold dry con- first and most important of the above tinental Polar air masses (Npc) as it three influences. The path of the cold moves southward towards the Gulf. air advance is over flat country all At this point it is necessary to inquire the way to the Gulf of Mexico, so that a little further as to what happens ho turbulence effects become no more the original Pc, or cPW, air-mass prop- pronounced than they are at Ellendale. erties in the course of the later history Table IV. of the mass. Pc — Modification of the Winter Source Air Winter (cPW Becoming cPK) (Surface and first 3 km at) Properties of the Pc Air to Npc Air Royal Center, Ind. Broken Arrow, Okla.

Following the first outflow of the T w RH fjE T w RH ftE Pc mass from the source region, "C g % "A °C g % °A —22.5 0.45 91 251.5 —14.8 0.96 86 260.5 where its properties are essentially —19.5 0.48 262.0 — 8.8 1.15 275.3 —15.8 0.48 276.5 — 8.0 1.20 285.7 data, those shown by the Ellendale —18.0 0.85 286.0 —10.3 1.03 294.3 there are three principal influences which may be at work to change these As long as the air mass continues properties. Observed changes of the moving over snow cover, there is only properties are to be explained then in a very slight warming and increase terms of one or more of the following of moisture to be observed. The air modifying influences: mass retains the characteristic cold- (1) Supply of heat by contact with ness of the surface stratum, though and radiation from the surface be- the cold layer becomes shallower, and neath, and supply of moisture by the temperature inversion sharper. evaporation from this surface. This This is doubtless due to subsidence, influence tends to make the lower i.e., the sinking and spreading of the strata of the Pc mass increasingly cold air mass. The Pc values of the warm and moist, or to change its air-mass properties given in Table properties from cPW to cPK. IV for Royal Center, Ind., and Broken (2) The effect of subsidence, which Arrow, Okla., are averages of ascents tends to intensify the temperature in- for the same period as those at Ellen- version at a low level and to effect a dale, January, 1930, in cases of mini- general warming of all the upper mum modification of the original Pc strata.* properties, i.e., in cases of the maxi- (3) The effect of turbulence occa- mum coldness and dryness of the orig- sioned by a rough undersurface in de- inal Pc air. Such cases are those where veloping a thoroughly mixed layer in the trajectory of the air mass the en- hilly or mountainous regions. tire distance to the point of observation As the cold Pc air mass moves has been over snow-covered ground. southeastward from the Canadian And this will be the case only for the border west of the Great Lakes across rapid outbreaks of cold air where the the Plains states and down through freshly outflowing cold air is displac- the Mississippi Valley towards the ing only slightly less cold air of the same source. Otherwise the modifica- *See J. Namias : Subsidence in the At- mosphere, Harvard Met. Studies No. 2, 1934. tion of the Pc properties takes place Also see figs 18, 19, on pp. 70-71 of this rapidly. booklet. much more 86 CHARACTERISTIC AIR MASS PROPERTIES

We notice in passing southward the southeastern states, and only with from Ellendale that the surface tem- mild outbreaks of Pc air. And it sel- perature of the Pc air becomes some- dom leads to fog formation, because what warmer, as would be expected, the cold air, being continental, is usu- but remains extremely cold. At Royal ally too dry. In Europe, on the other Center and Broken Arrow the surface hand, where the stagnation of the relative humidity remains very high, cold air masses is more frequent and and the temperature inversion in- prolonged, and where the Polar and creases slightly and becomes lower in Arctic air masses are frequently of elevation, w still increases with eleva- maritime origin and comparatively tion at all stations. These changes moist, this condition often leads to the are just what we should expect from widespread formation of fog or low a moderate degree of subsidence and stratus cloud, with practically zero- a slight increase of heating by ter- visibility below the temperature in- restrial radiation, and as a result of version. Above the inversion visibili- evaporation from a snow surface ties are always excellent. Of course, which is not here so cold as it is active overrunning of the Pc mass by farther north in the source region. a warmer moister air current com- Especially during the daytime is the pletely changes the type of weather. sun much more effective at the lower Such overrunning by warm Pacific air latitudes in raising the temperature in the Rocky Mountain region or by of the snow surface, and doubtless warm Gulf air in the Plains states mors heat is transmitted from the produces the typical blizzard condi- ground beneath, which is warmer, tions for these respective regions. through a snow cover which is thinner. As soon as a typical Pc air mass The characteristic curves for these leaves snow-covered territory, the stations representing their average modification of its characteristic Pc properties on the Rossby diagram properties becomes very rapid. Heat- are strikingly similar. And equally ing of the lower strata by contact uniform is the clear, dry, cloiidless with and radiation from the ground,, weather attending the passage of the and increase of moisture by evapora- Pc air mass, as long as it retains this tion from the ground surface, effect. characteristic temperature and mois- a rapid transformation of its prop- ture distribution. In the later stages erties, most marked nsar the ground of the Pc outbreak, if the cold air out- and diminishing aloft. At the same flow weakens and the conditions be- time that the lower strata of the air come stagnant, the gradually lowering mass are being rapidly warmed and and intensifying subsidence inversion moistened from the ground, there is is naturally attended by markedly de- doubtless also some direct radiational creased visibilities below the inver- heating of the upper strata in re- sion, particularly in industrial regions sponse to the increased terrestrial where smoke pollution of the atmos- radiation from the warmer ground phere is pronounced. It is, however, surface. The initial heating of the the exception rather than the rule for upper strata does not have to wait on such stagnation to follow in the case the establishment of thermal convec- of a strong outbreak of Pc air. The heating of the air stagnant anticyclonic condition with tion. The ground low subsidence inversion and poor mass is especially i-apid during the visibility usually occurs in the U. S. in daytime in southerly latitudes, where POLAR AIR MASSES WINTER

the clear skies characteristic of Pc quickly produces a discontinuity of the weather favor marked insolational other elements under these conditions. heating of the ground, and in particu- Generally speaking, the transforma- lar when the Pc mass is displacing a tion over land of the cPW to cPK air Tropical maritime air current, in mass has little significance for the which case the ground will be par- general weather conditions. Visibility ticularly warm and moist and the cold at the ground is improved, and apart air mixes with remnants of the warm from the possibility of the formation moist air. In this way under ordinary of a few cumulus clouds during the conditions the southern portion of an day, the skies remain clear. But the advancing Pc mass becomes rapidly effect of open water on the cPW air transformed, as it moves southeast- mass in winter is immediate and pro- ward across the U. S., from the typical nounced, the mass becomes cPK forth- source cPW properties of the air mass with. The addition of moisture and to a cPK, or unstable air mass, in heat to the cold dry air mass takes which the water vapor falls off rap- place very rapidly from any water idly with elevation to the low values surface. In surprisingly quick time aloft initially characteristic of the Pc the lower strata of the air mass are mass. This modified cPK form of the rendered convectively unstable, and Pc mass is designated as Npc on the heat and moisture are carried to suc- M. I. T. maps. cessively higher levels by active con- In contrast to the increasing instab- vection. The quantitative effect of ility of the Pc air mass as it is trans- this influence on the vertical distribvt- formed to Npc, should be noted the tion of temperature and specific hu- increasing stability of the Pp air mass midity will of course depend upon the as it is transformed to Npp. In the Pc air mass properties, the warmth extreme case the Npc mass, or part of the water surface, and the length of it, may be turned northward again, of the sojourn of the cold air over the become a return flow over a colder open water. The extreme degree to surface, and tend to a reestablishment which such a modification may go is of cPW stability. In general, this indicated by a comparison of the prop- rapid modification of the properties erties of our Pm air masses at Seattle of the southern portion of the Pc air with our Pc masses at Ellendale. Ori- mass relative to the northern portion ginally these two air masses have means that the initial horizontal homo- about the same properties, but the geneity of the air mass is destroyed, Pp is modified during its passage over or, in other words, the isentropic sur- the ocean. A still more extreme case faces do not remain in their initial is that of our Pc air which may reach horizontal position. This fact has long the Gulf of Mexico, under favorable since been remarked by Bergeron' as winter conditions, still as a very cold, characterizing all Polar air masses, dry and essentially stable mass. But and offered as the explanation of the the winter northers in the Central readiness of the Polar air masses American countries, which are invari- to form secondary fronts within ably continuations of our Pc out- themselves. Any wind discontinuity breaks across the Gulf of Mexico southward into the sub-Tropical cir- *T. Bergeron und G. Swoboda : Wellen und Wirbel an einer quasi-stationarer Grenzflache culation, are typically only moderately iiber Europa, Veroff Geophys. Inst. Univ. Leipzig, Ser. 2; Bd. Ill, no. 1, 1924. cool at the surface and attended by CHARACTERISTIC AIR MASS PROPERTIES

extremely heavy convective precipita- 0.5 g to perhaps 2.0 g, and the tem- tion. This change which takes place perature to have been raised by some in only 36 to 48 hours over the warm 10C°. This modification is a maxi- waters of the Gulf amounts often to a mum at the ground, disappearing at warming of the surface stratum of some 21 km elevation. In fact, the the Pc mass by 25° or even 30C°, thermal influence of the Great Lakes and an increase of w from perhaps 1 favors very markedly the formation to about 15 g. Unfortunately few of slowly moving shallow cold fronts soundings from these regions are in this region, which are indicated available, but they indicate a rapid at the ground by a well-marked approach to if not actual convective wind-shift from southwest to north- equilibrium under these conditions. west and a corresponding trough For the north-central and north- in the isobars. But observations of eastern U. S, the modification of the Pc winds aloft show always that at as air mass properties by the Great low as 2 km elevation this discon- Lakes is very important. During the tinuity has completely disappeared, late fall and early winter, while the the wind at that level being uniformly Lakes are still free of ice, this effect northwest. This means that from the is particularly well marked. On the Lake Region eastward to the Appala- coldest Pc outflows with a northwest chians the tendency is to a continuous wind blowing across Lake Michigan, overrunning of the somewhat modified for example, which is less than a hun- Pc air at the ground by colder Pc air dred miles wide, the temperature may aloft coming more directly from the be 10 °C, or even more, higher at source. This doubtless favors the ap- Ludington on the east shore than at pearance of the instability snow flur- Green Bay on the west shore. And ries which characterize the Pc weather whereas the sky will be cloudless at in this entire region. Green Bay, at Ludington there will The Pp Air Masses. The PP air be low ceiling and constant snow masses are those originating in the flurries. And this difference is char- Arctic or sub-Arctic, which reach the acteristic of all the Lake stations; Pacific coast of the United States or passage of the cold air across the Canada after a more or less pro- Lakes produces always a low Nbst or longed sojourn over the waters of Cunb cloud with almost continuous the north Pacific ocean. Initially snow flurries. Apparently the in- these air masses come from the Arctic stability layer produced over the source regions with properties which Lakes is rather shallow, as evidenced probably approximate those which we by the characteristic lightness of the have found to be characteristic of Pc precipitation and the amount of the air, but prolonged heating and moist- temperature increase in the ground ening over the warm waters of the stratum of the air mass. However, north Pacific produce, to an extreme it is marked enough so that consider- degree, the type of modification which able cloudiness with snow flurries we found to be effected in the P(' characterizes the Pc current from the air masses in winter by the Great Lake region eastward up the moderate Lakes. They are changed from a slopes to the Appalachian Divide. cold, dry, extremely stable condi- The surface values of w are found to tion to one of marked conditional have increased in passing over the instability vdth a comparatively high Lakes from a normal value of about moisture content in the lower strata. POLAR AIR MASSES—WINTER 89

The data from Seattle in Table III to be low and thick and the precipita- give the average conditions in the Pp tion (snow in the mountains) to be air mass as it arrives on the north heavy and almost continuous. Such Pacific coast direct from more north- conditions will persist as long as the erly latitudes. When these air masses steady onshore flow of the Pp air have made a swing southward and continues. reach the Pacific coast from the west It happens quite frequently in win- or west-southwest they are still ter that a westerly flow of air from warmer and moister than indicated the Pacific (usually Pp air masses) by the data from Seattle in Table III continues for considerable periods of but especially so in the upper strata. time, so that the weather conditions Consequently, the convective instab- prevailing over the greater part of ility is less pronounced and is dis- the United States may be dominated placed upward to the higher strata of by these air masses. We have just the air mass. seen the unfavorable weather condi- If we compare the properties of the tions which prevail in the Pp air cur- Pp air mass at Seattle with those of rent in the Pacific coast region but the Pc at Ellendale, we note that, this air mass is importantly modified whereas at the ground the former in crossing the western mountain is 34 °C warmer than the latter and ranges to the interior of the country has a specific humidity nearly 15 in the following ways: times as great, at the 3 and 4 km (1) Much of the moisture con- levels the temperature difference is tained in the lower strata of the Pp only 6 or 7°C, while the difference in air mass is condensed in heavy con- the specific humidity almost vanishes. vective showers and the heat of con- Probably 3 km is about the upper densation is supplied to the air mass limit to which convection has pene- strata at intermediate levels. trated in the Pp air mass. The equiv- (2) The descent of the eastern alent-potential temperature at this slope of the Rockies dissipates the level is somewhat lower than at the cloud deck and convective showers in ground but it begins to increase the Pp current, while the heat of con- rapidly above. densation already supplied to the As would be expected from the intermediate strata of the air mass conditional instability and high moist- and adiabatic compression (fohn ure content of the lower strata of the effect) cause a marked warming of Pp air mass on the Pacific coast, fly- the air mass at the 1 km level and ing weather conditions are not favor- above. able in the Pp current. Visibility is (3) The warming of the surface good in the absence of condensation strata is checked by radiational and forms but we find normally a rather contact cooling over the cold con- low broken cloud deck, which may be tinental surface and perhaps also by solid over large areas, with extensive mixing with remnants of the cold Pc cumulo-nimbus formations and con- air. vective showers which are frequently The effect of these various influ- rather heavy and may follow in quick ences acting on the Pp air mass is succession. Winds are likely to be readily seen by comparing the Pp gusty, and flying extremely bumpy. data in Table III from Seattle with On the western slopes of the coastal those from Ellendale, which may be mountain ranges the clouds are likely taken to typify inland conditions in 90 CHARACTERISTIC AIR MASS PROPERTIES

this air mass. At Ellendale the Pp air current comes in contact with a air mass shows a very large tempera- strong outflow of cold Pc air on the ture inversion and constant value of eastern side of the Rockies, it is w in the first km, instead of the likely, as the warmer current, to instability found at Seattle. The ascend and advance over the Pc cur- temperature increase over the Seattle rent along a typical warm front. values shows a maximum at the 2 Such a development may cause severe km level. Probably, however, the blizzard conditions in the Plains marked increase in T and w found at states, but this is, of course, a 1 km and above, in passing from frontal phenomenon and in no sense Seattle to Ellendale, is considerably a characteristic of the Pp air mass. in excess of the change which actually occurs in the air current itself, Polar Atlantic Air Masses in Winter for the Pp current which reaches Ellendale comes from the west or [Owing to the prevailing west-east air the North Atlantic is west-southwest. It is not one of the movement source direct northwest currents such as not an important region for air affecting America, Seattle's data represent but one of masses North especially in winter when this move- the westerly currents which is doubt- ment is strongest. The source region less appreciably warmer and moister for air affecting the S. is the at upper levels than the fresh Pp air Pa U. Atlantic adjacent to from the northwest. However, the part of the N. Ellendale data are absolutely typical the continent and north of the warm Gulf Stream, from the Gulf of Maine for the Pp air masses which have abnor- crossed the mountains to the interior north, where the waters are mally cold in winter of the United States. The modifica- the year round; only effect a modification from the typical coastal Pp these waters tion of air masses which move off properties is so pronounced that the Pc the continent and which may occa- symbol Npp instead of Pp is used for westward as Pa these air masses in the central United sionally retrograde coast, where States. air onto the eastern distinct from those The weather conditions which pre- its properties are of other air m^asses. As it moves vail in the Npp air masses east of the off coast the anticyclonic circula- Rockies are in general the best which the of Pc air brings are experienced in winter. Air move- tion of a large body the old Pc, modified into Pa, onshore ment is usually moderate, and convec- again as a NE wind backing to SW, tive turbulence is experienced only return flow may be strength- in the afternoon when the large which approach of a disturb- diurnal temperature range found ened by the (warm current) from the S or under these conditions may be suffi- ance brings a sudden change of cient to overcome the normally pre- SW; it seldom reaches beyond vailing surface temperature inver- weather but Appalachians. sion. Temperatures are notably the mild, skies clear except possibly for The vertical structure of Pa on the some scattered high clouds and visi- north Atlantic coast of U. S. (Boston, bilities generally very good except e.g.,) is characteristically dry and for the possible occurrence of morn- stable aloft, with a fairly shallow, ing smoke haze in industrial regions. cold and moderately unstable moist When, however, an advancing Pp layer at the surface; the lower levels —

TROPICAL AIR MASSES—^WINTER 91

Masses. The are colder, drier and more stable than The Tropica! Air origin- in Pp air (at Seattle, e.g.) because Tg air masses are those which the waters (0°C) are colder and the ate over the warm waters of the Gulf Sea, or air has spent much less time there- of Mexico and Caribbean over. The upper levels show the further southeast in the Tropics. typical structure of old Pc air, much Scarcely to be distinguished from warmed and dried by subsidence, and them in characteristic properties are above 3 km the warm-front inversion the Ta air masses from the Sargasso (often due to tropical air) of the Sea region, so that this discussion next approaching disturbance may really applies to both. The Tp air already be present. masses are the Pacific counterparts of Tg or Ta. The transitional forms On the coast, therefore, the Pa air these masses are usually referred has a surface temperature near freez- of to simply as Ntm (transitional Trop- ing or somewhat below, with a good ical maritime). There is no attempt lapse-rate through the first km, more to make the very difficult distinction or less, the relative humidity rather between Ntg and Nta. high (w = 2 or 3 g/kg) and increasing to saturation or nearly so at the The Tropical Pacific Air Masses top of the convective layer, where The source of the Tp air masses is there is a deck of thickening Stcu; that portion of the Pacific Ocean but Cunb and showers are prevented Ij-ing west and southwest of southern by the marked inversion a short dis- California, roughly between latitudes tance above the cloud base. Above 25° and 35 °N. During the cold season the inversion it is dry, and clear this region is one of markedly steady unless there are warm-front clouds weather conditions, as it is normally still higher. At Boston, for example, the winter seat of the stationary Paci- the Pa air arrives rather suddenly fic anticyclone. Over the Pacific following a rapid backing of the wind Ocean north of lat. 30°N we find from NW to NE, with thickening low normally in winter a pressure gradi- Stcu clouds scudding in from the ent directed northward towards the E; later light flurries or fine mist Gulf of Alaska and the Aleutian begin, making poor the already fail- Island Region, which is the winter seat ing visibility, and the temperature has of the north Pacific low pressure area, 10 risen perhaps as much as °C; the usually referred to as the Aleutian front of the maritime air works Low. From or around the Aleutian steadily inland, abruptly terminating area move most of the winter frontal cold weather, till it nestles in the systems and disturbances which ap- lee of the eastern ridges of the Appa- proach the north and central Pacific lachians. Farther south this type of coast. When these disturbances fol- onshore flow is much warmer owing low an unusually southerly path, or to the nearby Gulf Stream, and un- develop secondary centers which move stable to higher levels due to its the usual Pacific longer maritime history; but here further south than reports are often insufficient to prove depression, or develop in themselves then the Trop- Polar origin—it should be called Pa to an unusual intensity, or Npa if traced from Pc, otherwise ical maritime air lying in the northern Ta or Nta. Npa is Pa air warmed portion of the Pacific anticyclone is and unstable beyond typical Pa con- set in motion towards the northeast ditions. R. G. Stone.l in response to the intensified pressure 92 CHARACTERISTIC AIR MASS PROPERTIES

gradient toward the north or north- moderate to heavy convective showers west. Occasionally an extension of in the warm current much more the anticyclone northeastward towards probable. the California coast occurs, causing The properties of the Tp air mass the establishment of a pressure gra- may be anticipated to some extent dient which brings a general flow of from the nature of the source region. Tp air northward along the entire The ocean surface in this region is length of the middle Pacific coast even rather cool for the latitude, ranging beyond Seattle. Thus in advance of in temperature during the coldest the southern portion of the cold front season from about 14° C at latitude or the occluded front which marks 35 °N to about 19° C at latitude 25 °N. the southward advance of fresh Pp The w^eather condition is prevailingly air behind the depression approaching anticyclonic, which suggests the proba- from the northwest, we may find a bility that more or less subsidence is broad open warm sector of Tp air taking place aloft. Thus we should moving northeastward or even north- expect to find that the air masses ward along the coast with rather high which come from this region are only wind velocities. Frequently this warm moderately warm, or even cool for sector is occluded before the warm Tropical maritime air, at least near air reaches the coast, especially when the ground. We should expect to find the coastal region is covered with cold these air masses also relatively stable, continental air. Under these condi- perhaps with indications of a subsi- tions California gets its heaviest win- dence inversion which should be ter rain, caused by condensation both marked by an abrupt decrease of the within the Tp air aloft, and also w. w should be moderately high near within the follov/ing unstable Pp air the ground, but definitely not high for as it overruns the cold continental a Tropical maritime air mass. Finally, air (warm-front-type occlusion). The we should expect to observe an ab- occasional winter development of a scence of condensation forms in this marked depression inland as far as air until it has moved some distance the Great Basin or the southern Pla- northward from its source and has teau region of Nevada and Utah, ac- been appreciably cooled from below. companied by widespread heavy pre- However, the data for San Diego in cipitation, is apparently associated Table V probably give a fairly good with marked overrunning at high picture of the Tp properties in this levels by Tm (either Tp or Tg) air region. The temperatures we notice from the south. On the other hand, are rather high at all levels, though the Tp air frequently sweeps north- not markedly so considering the prox- ward along the Pacific coast with imity of the maritime Tropical source little or no resistance by colder air and the southerly latitude. The sur- masses, consequently without appre- face temperature is about 2C° higher ciable overrunning at the warm front than the water temperature off the and with little or no rain before the coast at San Diego, a fact which in- approach of the cold front. A simi- dicates a moderate recent movement lar development may take place also of the air from a warmer region. We along the Gulf or Atlantic coasts, but notice also the marked stability of the in general the greater warmth and lowest km of the air mass, as well as moisture content of the Tg and Ta the large decrease in w, both facts air masses make the occurrence of which indicate either a low subsidence TROPICAL AIR MASSES—^WINTER 93

inversion or a low turbulence inver- as tVie difference observed at San sion. The rather surprising frequency Diego between the value at the ground of low St or Stcu clouds in the Tp air and that at I km, otherwise the de- mass at San Diego seems to favor the crease would not be so large. Above second possibility. If the air mass was 1 km we note a stable lapse rate, but originally characterized by marked one which increases somewhat with stability and a rapid decrease of w elevation. The decrease of moisture with elevation at low levels, then the noted in the first km continues at decrease of w at an inversion pro- higher elevations, but especially mark- duced by turbulence might be as large edly at the 3 km level. Table V

Tropical Pacific Air- Elevation San Diego

T w RH (9e °C g % °A :

94 CHARACTERISTIC AIR MASS PROPERTIES

dicate a large degree of turbulent presence of another air mass aloft mixing up to a considerable elevation which is designated as S, or Ts (Trop. in the Tp current. This marked tur- superior), air. bulence probably is a consequence of This designation is used for that the high wind velocity M^hich must warm, dry air mass which is found characterize any winter air current to be present a great deal of the of Tropical origin reaching Seattle, time over the southern U. S. at inter- and of the ruggedness of the north mediate and upper levels and fre- Pacific coast. But in its general char- quently over the central U. S. at acteristics the air mass is found to be somewhat higher levels, at all seasons at Seattle as it was at San Diego, of the year. It is the warmest air warm, moist, and relatively stable. mass observed, averaging a few de- As at San Diego, we note that ^E in- grees warmer than Tg at intermediate creases slightly with elevation, a fact levels but, owing to the steep lapse- which indicates the absolute convec- rate frequently observed in it at tive stability of the mass. Consequent- higher levels, above about 5 km, it is ly as at San Diego the air mass is likely to average slightly colder than characterized by stratiform clouds, Tg. It has a relative humidity less and by the restriction of any con- than 40%, which is often observed siderable amount of precipitation to to fall below 20% or even 10% in the frontal zones. The characteristic the upper strata. Normal values (not curves on the Rossby diagram for Tp computed means) of the temperature air at these two stations are closely and specific humidity of this air mass parallel and their approximate coin- at the 2 km level, at San Antonio, cidence with the dE isotherms is Texas, and Omaha, Nebraska, for striking. A comparison of these curves January and July, might be given as with the characteristic curves of the follows Tg and Ta air masses wall call to at- January July tention at once the comparative insta- Tsat2km T q T q bility of the latter air masses, which San Antonio 10°C 3g 24°C 5g is indicated by their more nearly hori- Omaha 5°C 2g 22 °C 5g zontal course on the diagram. At higher levels q frequently falls The Tg and Ts Air Masses to half a gram or less, and even in As would be expected from the summer to less than a gram. uniform warmth of the waters in the The hot dry weather which occurs Tg source region, marked warmth in the western Plains states in sum- and high moisture content at lower mer and in the Southwest even in levels is characteristic of these air winter, is always associated with the masses. This is shown strikingly in presence ol this air mass at inter- Table III by the high values of T, w mediate levels and frequently, especi- and at the surface and the 1 km E ally in summer, even at the ground. level in the Tg air, values which are It occurs frequently above a shallow much higher than are found in any stratum of moist Tropical maritime other American air mass in winter, air at the surface, but on summer But at Groesbeck we find at the 2 afternoons this moist stratum is and 3 km levels a surprisingly large likely to be lost by convective and decrease in the moisture content of turbulent mixing into the dry Ts the air mass. This decrease of moist- strata above. ure is best interpreted as due to the It is the first air mass designation TROPICAL AIR MASSES—WINTER 95

to be used at M. I. T. which obviously higher altitudes. This condition pre- does not apply to a mass of surface vails a great deal of the time in the origin. For this reason it was clearly southern U. S., accounting for the identified and designated as a separate prevalence of the Ts air there. Much air mass only after rather much experi- of this air probably comes to us from ence in the use of aerological data in the eastern regions of the Pacific preparing atmospheric cross sections. anticyclone, after crossing the Rocky Formerly it was treated simply as a mountains.* Probably fohn effects on dry upper stratum characteristically the eastern slopes of the Rockies help present with the Tropical maritime to bring the Ts air down to the sur- masses, and not as a distinct air mass. face, and to give it the particularly However, it has been found to be of high temperatures observed in the much wider distribution than the Southwest. However, the appearance Tropical maritime masses, occurring of this type of air will be by no means above polar as well as Tropical mari- restricted to this region, but should time masses, and obviously requiring be noted throughout the southern separate treatment as a distinct air temperate latitudes of the continent. mass. Recent studies in isentropic analysis In winter at least, the Ts air mass by Mr. J. Namias show quite def- seems to be of tropical origin, as in- initely how in summer many of the dicated by its warmth, and with an so-called Ts currents are apparently extended past history during which Pc air masses that have swung around it has remained aloft, as indicated by anticyclonically from the eastern Ca- its dryness. Consequently the logical nadian source region and subsided. source region to attribute this air Thus the heated continent and the mass to is the upper portion of the seasonal shift of the Westerlies bring sub-tropical belt of high pressure.* the Ts source region well north in that slow sinking of pole- We know summer. (See art. X.) ward moving air must be occurring In spite of the marked potential in this region. This sinking is especi- instability of the Tg air masses in ally concentrated in the great anti- the south, their thermal stability is cyclonic cells in the sub-tropical high such that convective precipitation pressure belt, and according to the occurs rarely within the air mass in scheme of J. Bjerknes, especially on winter. But from the warm front the northern and eastern sides of at which the overrunning warm cur- these anticyclonic cellular units. rent is Tg air, the precipitation is Hence we should expect to find this often convectively irregular and ex- warm dry air predominating where tremely heavy. With the high rela- we have prevailing west or west- tive humidity observed in the lowest northwest winds at intermediate or km of the Tg current, comparatively upper levels in south temperate lati- little forced ascent of the warm cur- tudes. We should expect to find this rent is necessary before the potential current at higher levels further north, instability present becomes available owing to the increasing prevalence for thermal convection. In fact it and depth of the polar air masses at occasionally happens even in winter

*See my "Disc, and Illustr. of Problems. . . . of Cross-Sections," M. I. T., Papers in Phys. designation has supplanted the Ocean and Met., Vol. 4, No. 2, 1935 ; and G. ^The Ts (tropical continental) designation on Emmons : Atmospheric Structure over So. U. S. Tc Dec. 30-31, 1927, M. I. T. Met'l Course Prof. the North American weather maps, for there this Notes, No. 9, 1935 (rev'd Bull. Am. Met. Soc, is no really extensive Tc source region on Aug.-Sept. 1936, pp. 268-271). continent. The Wea. Bur. uses "S" for Ts. 96 CHARACTERISTIC AIR MASS PROPERTIES

that sufficient forced ascent of a As the Tg current moves northward vigorous Tg current is effected by it is continuously cooled in the lower- coast line or mountains (southern most strata by contact with the in- Appalachians) so that convective creasingly cold surface beneath. showers are initiated, but this occur- Over dry land this cooling takes place rence is restricted for the most part rather slowly but over cold water or to the summer season when insola- a snow and ice surface it becomes tional heating of the Tg air mass may- very rapid. The natural consequence produce widely scattered heavy con- is to produce very rapidly a super- vectional thunderstorms in the east- saturated stratum at the ground in ern United States. the warm moist air current. If the In the south the prevailing weather air movement is light, this leads conditions in the Tg air mass are quickly to the formation of dense fog essentially those of warmth and high at the ground (the so-called Tropical- humidity. There is likely to be a air fog") but since the advance of Tg good deal of cloudiness, especially air to high latitudes is normally asso- during the night and early morning. ciated with rather strong air cur- The principal cloud forms are rather rents, mechanical turbulence usually low stratus or strato-cumulus, which maintains a thoroughly mixed stra- the sun frequently dissipates during tum at the ground, topped by a dense the day. Visibility is likely to be low stratus cloud deck. As the cool- rather poor when low clouds prevail ing continues, rather dense mist or but becomes good with the dissipa- fine drizzle is likely to fall from this tion of the cloud deck. The cloud stratus, so that the visibility even base is likely to be at only a few with rather strong wind may be re- hundred meters elevation, while the duced almost to that of a dense fog, upper boundary coincides with the with a ceiling of not more than one temperature inversion which marks or two hundred meters. This is a the upper limit of the extremely moist condition which makes fiying practi- air stratum, usually between 12 and cally impossible, except over a per- 16 hundred meters elevation. It is fectly fiat surface. Long before seldom that any precipitation is asso- visibility becomes poor at the ground ciated with this type of stratus in the lowering ceiling in the advanc- the south, for the inversion above is ing Tg current makes fiying in moun- usually sufficient to prevent penetra- tainous country difficult. For ex- tive convection and, in its earlier his- ample, even in the lowest passes in tory near the source region, the lower the Appalachians the ceiling quickly strata of this air current are not suffi- closes in, especially on that side of ciently cooled to produce the mist and the ranges against which the wind is drizzle which are likely to appear as blowing. it moves northward. Apart from the The data in Table III for Tg air at possible existence of a turbulent Boston show clearly the beginning of stratum near the ground in cases of the cooling of the Tg air mass to the strong air movement, flying condi- Ntm condition, as just described. As tions in the Tg air mass should be compared with Groesbeck we note the definitely smooth in the south. Fre- marked stability of the first km of quent low stratus and rather poor visibility may prove embarrassing, sSee H. C. Willett: Fos and Haze, Their Causes, Distribution, and Forecasting, Month- especially in hilly country. ly Weather Review. November. 1928. POLAR CANADIAN AIR —SUMMER 97 the air mass at Boston, where ob- sence of marked frontal activity. We viously the 1 km level is just above have seen how the study of the char- the top of the surface turbulence acteristic air mass properties as in- stratum. But equally striking in the dicated by the aerological observa- comparison of the data at these two tions facilitates the understanding stations is the disappearance of the and explanation of these weather dry Ts strata between 2 and 4 km types and consequently favors especi- at Boston. For some reason the moist ally the forecasting of those, elements Tg air mass averages much deeper which are important in aviation. at Boston than in the southwest. This Moreover, recent aerological investi- seems to be a result of the strong gation of frontal activity and of the flow of the Tg currents in this region development of cyclonic disturbances and the horizontal convergence which here and abroad show that the air accompanies active cyclogenesis. The mass properties are also of much dry Ts air mass is usually found importance for the explanation and here above the 4 km level. forecasting of all those phenomena The weather types which we have which depend upon interaction at the discussed above in connection with the boundary between air masses of principal air masses, are the predom- markedly different properties (see inant types which we meet with in the article by Haurwitz and notes by United States, in winter, in the ab- Bergeron, elsewhere in this booklet). V. SUMMER AIR MASS PROPERTIES! The Pc and Npc Air Masses the field of observation it has ac- During the warm season the source quired about the same characteris- properties of the American Pc air tics. These characteristics are typi- masses are very different from those cally as follows (C/. Figs. 16-18 of characteristic of the cold season. The Art. VIII-IX by Namias) :— snow cover which is always present (1) A fairly low moisture content over this source region during the (low compared with that of summer- colder half of the year completely time air masses of more southerly disappears, and the bare ground sur- origin). The values of w at the face becomes much warmed during ground usually are near 5 or 6 grams, the long summer days. Consequently and decrease steadily with elevation. instead of being cooled from beneath Relative humidity is also low, especi- as in winter, the Pc air masses are ally during the warmer time of day, heated from the ground. Even though so that conditions are favorable for the air mass may originate over the the steady supply of moisture by cold waters of the Arctic, it quickly evaporation from the warm ground loses the coldness and stability of its and its transport upwards by convec- lower strata over the warm land. It tion. It is probably in this way that the observed moisture distribution is usually impossible to tell from its has been established. With increas- properties whether the air mass came ing age and displacement southward initially from the ocean or not. This of the air mass the w values increase holds for the Pacific as well as for steadily at all levels from the ground the Arctic Ocean, for in any case by up. the time the air mass has crossed the (2) A moderately low tempera- western mountain ranges or moved ^Excerpts and abstracts by R. G. Stone from southward from the Arctic Ocean to 'American Air Mass Properties," 1933. 98 CHARACTERISTIC AIR MASS PROPERTIES POLAR PACIFIC AIR—SUMMER 99

reservoir in the north as they do in the air has been moving inland from winter, they usually appear more in the sea. It must be explained rather the nature of almost stationary deep as the result of turbulent mixing northerly currents (more NW-ly in effected in an air mass initially mod- winter) that may remain in the same erately stable by its passage over the longitudinal zone for several days. mountainous promontories or along Thus Royal Center in summer does the devious water route to the head not, as in winter, get Pc air that has of the fjord where Seattle is located. passed first over EUendale, but rather The constancy of w, and the increase directly out of the north, with the re- of the relative humidity from an sulting differences mentioned above. average surface value of 62% to an At Pensacola, Fla., the maximum average of 91% at 1 km is further m.odification (to Npc) of the original evidence of the correctness of this Pc properties may be seen; note the assumption. Stcu clouds are nearly high w and some decrease in with always present with a base elevation elevation, which indicate conditional between 8 and 14 hundred meters instability, especially in the after- under these conditions. But the Cu- noon, so near to actual instability nb clouds and showers characteristic that local thundershowers may de- of the Pp air mass in winter are definitely absent. reason is velop. The surface temperature is The not far from the lower limit for Tm obvious when we note a lapse-rate air in summer (340°).—R. G. S.] between the 1 and 3 km levels of only four-tenths of the dry adiabatic The Pp Air Masses rate, whereas in winter between these Generally speaking, we expect to levels we found a lapse-rate of more find in summer all maritime air than seven-tenths of the dry adia- masses relatively stable, and conti- batic rate. The large decrease of w nental masses relatively unstable, to be noted in the Pp air mass in compared with their winter vertical summer between the 1 and 2 km structure, because of the seasonal levels is noteworthy as indicating defi- reversal of the normal temperature nitely that between these levels must differences between land and water lie the upper limit of the turbulence surfaces. We have seen that for the layer and doubtless therefore of the Pc air masses this difference is very Stcu cloud layer also. pronounced, that the condition of extreme stability of the winter conti- Table VII. nental Polar air is changed in summer to a condition of moderate instability, especially marked during the daytime. But a glance at the summer properties of the Pp air mass at Seattle at upper levels (Table VII) shows the presence of a surprisingly good lapse- rate, especially through the first km. Since all the Seattle ascents were made during the early morning hours, this surface instability cannot be explained as the result of insolational heating during the short interval that 100 CHARACTERISTIC AIR MASS PROPERTIES

is characterized by greater stability Pc air. In summer we find the Pp between 1 and 3 km than is summer air mass cooler than the Pc mass Pc air at the inland stations, never- at all levels, and above the first km theless, no condition approaching iso- just as dry. The relative coolness thermalcy is found at any level in of the maritime Polar air mass in the Pp air masses, but rather quite summer depends primarily upon the an appreciable lapse-rate at all levels. coolness of the ocean surface relative Furthermore, we find that from 1 to the land surface. Not only are km upwards the Pp air mass is the lower strata of the maritime air markedly colder than the Pc mass at mass less heated by their contact any of the inland stations. The tem- with the earth's surface than are perature found at SVz km in fresh Pc the same strata of the Pc mass, but air at Seattle is the same as that ob- there is also less terrestrial radia- served at 4 km in Pc air at Ellendale, tion from the cool water surface to where this air mass is colder aloft the upper layers of the maritime air than at any of the other inland mass. The absence of the marked stations. Furthermore, the values of heating by contact which occurs in w at Seattle are slightly less than winter at the warm ocean surface is those in the Pc air masses at Ellen- reflected also in the low elevation to dale and Royal Center. Rather note- which the dampness of the summer worthy is the marked constancy of Pp air mass extends, i.e., the small equivalent-potential temperature in vertical extent of the penetration of the Pp air at Seattle. This constancy mechanical or convective turbulence. of 6 indicates the absence of poten- Nevertheless, the lapse-rate in the E air at Seattle is tial instability at any level of the Pp summer Pp masses to indicate that the air air mass, but on the other hand it steep enough definitely does not represent the flow has been from colder to warmer stable structure of an air m.ass cooled surfaces. Probably the heating is from below. rather gradual during the progress The coldness and dryness of the of the air mass from the cold Polar seas southward. This heating prob- summer Pp air masses at Seattle in- ably effective at upper levels dicate almost conclusively the cor- becomes of direct radiation rectness of the assumption, based on only by means the surface beneath without the study of the winter properties of from mechanical or convective turbulence this air mass type, that the source of having played any role above an ele- the air mass is the same as that of vation of about 1 km, which we found the Pc mass, or at least that it is as depth of the tur- truly Polar or Arctic in character. In to be a normal winter we found that although the bulence layer at Seattle. lower strata of the Pp air mass were But there is besides the relative ;greatly warmed and moistened by the coolness of the water surface in sum- warm ocean, the upper strata were mer another fact which should not quite as dry and only a little warmer be overlooked in the explanation of than the same strata of the Pc air the coolness of the Pp air masses at mass at Ellendale. In fact, recent this season. This fact has to do with observations extending to higher the change in the normal atmospheric levels indicate that above 4 km the pressure distribution along the north Pp air masses are frequently, and Pacific coast from winter to summer. even in winter, colder than the In summer the pressure is relatively POLAR PACIFIC AIR—SUMMER 101

low over the continent, and relatively approximate surface fog in their low high over the ocean, especially over elevation in the upper portion of the the northern area, so that in summer turbulence layer. The extreme local the middle Pacific anticyclone extends coldness of the ocean surface along far northward into the region nor- the California coast is sufficient to mally occupied in winter by the so- cool the lower strata of even the called Aleutian Low, which tends to coolest Pp air masses from the north- be displaced inland from its winter west. position with greatly diminished in- It is quite impossible in summer to tensity. Consequently in summer distinguish air of Polar Pacific origin there is normally prevalent a well- from that of Polar continental origin marked pressure gradient directed after the former has reached the from ocean to continent along the aerological stations in the interior of entire Pacific coast from California the U. S. In summer most outflows northward, a condition which favors of Polar air over North America first a steady transport of Polar maritime become evident in a strengthening of air southeastward along the entire the normal pressure gradient along Pacific coast. This condition is so the Pacific coast, and consequently persistent in summer that warm mari- in an intensification of the Pp air time air from the south seldom if flow. This northerly current gradu- ever reaches the north Pacific coast ally works inland, with an accom- at the sui-face directly, as it fre- panying general rise of pressure in quently does in winter. Occasionally the coastal region, and a gradual there occurs a temporary cessation of displacement eastward of the zone the maritime Polar outflow on the of strongest north or northwest north Pacific coast during the pas- winds. Consequently the Polar air sage further north of a disturbance current becomes increasingly conti- following a more southerly course nental in its composition as the Polar than is usual in summer. Further- source region from which the outflow more, the ocean surface temperature takes place is displaced continually along the California coast is so low inland, or eastward. Under these in summer, because of the upwelling conditions it becomes almost impos- of cold water, that Tropical maritime sible to determine a boundary be- air masses must pass a great distance tween the air current of maritime northward from their source region and that of continental origin. In to reach the latitude of Seattle. winter this distinction is easier to It seems very probable that the make, because of the very much change at San Diego from the Seattle greater coldness and dryness of the values of the Pp air mass properties continental air. But in summer when would be in the direction of a marked the initial differences between the increase in stability, especially at the Pp and Pc air mass properties are surface. Probably even in the pre- so slight, by the time that the Pp mass vailing air flow from the northwest has crossed the mountains, usually we would find a pronounced low tur- rather slowly, and come probably bulence inversion (the wind veloci- into radiation equilibrium with the ties are usually too great to permit continental surface beneath, all dif- of the formation of a surface tem- ferences between these air masses perature inversion) with dense St or are so completely obliterated that it Stcu clouds, which may at times is neither possible nor of any advan- 102 CHARACTERISTIC AIR MASS PROPERTIES

tage to distinguish between them. may amount to as much as 20° or Consequently the designation Pc can 25 °C. Usually, however, the Pa air be used indifferently, in summer, for masses in summer do not make their Polar continental air masses or Polar influence felt south of Cape Hatteras, air masses of Pacific origin after they and the greater part of the time only have reached the interior of the U. S. on the north Atlantic and especially —Excerpts. the New England coast. The Pa Air Masses The term Pa, in summer as in win- The Polar Atlantic air masses are ter, is applied to those air masses more important in the late spring which were originally Pc, but which and early summer than at any other have remained long enough over the time of the year. At this season the cold waters of the north Atlantic to ocean surface in their source region, have become appreciably modified. from' Cape Cod northeastward to We have seen that in winter very Newfoundland, is at its maximum of little time is required to effect such abnormal coldness for the latitude a modification because of the marked initial coldness air and at its coldest in comparison with of the mass. In the continental region to the west. late spring and early summer, how- This relative coldness is a conse- ever, the water surface is colder quence of the slowness of the cold than the surface strata of the Pc air, continental ocean current from the so that the modification takes place north in warming up in the spring, slowly. On the other hand, the gen- and possibly in part to the drift of eral stagnation of the air movement this is fre- ice into this region with the Labrador over north Atlantic area current. It follows that this ocean quently so persistent at this time of region in late spring and early sum- year that the air mass may have days mer becomes a real cold air source. in which to reach a condition of equi- Whenever the normal eastward move- librium with respect to the surface ment of air over this region ceases, beneath. As the stationary maritime as it frequently does in the spring anticyclone develops under these con- and summer, the tendency is towards ditions, the cold air usually reaches the immediate development of a sta- the coastal stations at first as not tionary anticyclone thermally main- much more than a sea breeze, but on tained by the cooling of the stagnant the following days the cold air mass air mass present in the region. Such usually invades the whole coastal area developments frequently manifest east of the Appalachian Mountains, surprising persistence over the cold and occasionally advances far to the water, and usually lead eventually to south. The properties of the cold air an overrunning of the north Atlantic mass are shown best by the New Eng- coastal region by the cold Pa air of land coast stations, although in the the anticyclonic circulation. Occa- case of a southward displacement of sionally it happens that a general the air mass the characteristic cold- southward movement of the cold air ness is retained to a surprising de- follows down the entire Atlantic gree. The surface air temperature of coast as far south as northern Flor- the mass, as indicated by an outlying ida, bringing with it a decided drop station like Nantucket, is probably in temperature. The difference in very close to that of the cold ocean temperature between this cold mari- surface from which it is moving. This time air and the hot continental air temperature is likely to be about 5°C POLAR ATLANTIC AIR—SUMMER 103 at the beginning of May, about 10 °C or completely disappearing. Precipi- at the beginning of June and 12° to tation never falls from these clouds 15 °C later in the summer. There is in summer. This follows from the almost no daily period in these tem- initial dryness of the Pc air mass, peratures. In spite of the fact that and the very small amount of evapor- these temperatures indicate a cooling ation which takes place from the cold of the air mass from the temperature water in summer. There is very which it originally possessed over the little difference between the specific continent as Pc air, the Pa air mass humidity of the Pc and that of the Pa is found to have just as in winter air mass at this season. The cooling a rather unstable structure up to of the air mass at the cold water about 1 km. Since this lapse-rate surface, an effect which we assume cannot be explained in this case as to be carried upward by turbulence, caused by heating from below, me- produces usually a thin saturated chanical turbulence remains as the stratum at the top of the turbulence only obvious explanation of the in- layer (as indicated by the cloud form- stability of the lower km of the Pa ations mentioned above), but seldom air mass. Stratiform cloud forms more than about 70% relative hu- indicate a marked inversion at the midity at the surface. Hence the real top of the turbulence layer. It is Pa air mass does not become foggy very probable, in view of the pre- over the water, but is on the contrary vailingly stagnant anticyclonic con- usually characterized by excellent dition associated with this air mass, horizontal visibility, apart from the that the inversion is intensified by occasional thin cloud layer men- continual subsidence of the upper tioned above. There is, however, strata of the mass. The wind velo- occasionally visible over the ocean city is usually strong enough in the on a clear afternoon in this air mass cool maritime anticyclone to justify a very noticeable whitish haze, even the turbulence explanation of the un- when the relative humidity is appre- stable ground layer of the Pa air ciably below saturation, and the con- mass, and the long exposure of the dition is far from being one of real mass over the cold water could ac- fog. This may be due to the presence count for the loss of much heat from of tiny water droplets on salt nuclei. this stratum by turbulent transfer It is obvious that the general effect downward to the cold surface. Two of the underlying cold water surface April ascents at Boston in this type in the source region of the Pa mass of air mass showed a lapse-rate in summer is to effect a cooling of nearly nine-tenths of the dry adia- the air mass from beneath making batic rate up to 1 km, where there it essentially stable, though this is was a thin Stcu cloud layer, with a apparently counteracted close to the temperature inversion immediately ground by turbulence. Once the Pa above of 5°C. We find typically in air comes over the warmer land it the Pa air mass in summer some St or rapidly becomes warmed from below Stcu or Frst clouds at the top of and hence more unstable. the instability layer, though they are It should be mentioned at this usually much thinner than in the point that warm, moist, continental same mass in winter, seldom covering air in summer, and even more Tropi- the entire sky, and frequently ap- cal maritime air masses from the pearing as only a few scattered Frcu Gulf Stream, which move into the —

104 CHARACTERISTIC AIR MASS PROPERTIES

Pa source region, are very quickly continental outfiow of air with some cooled over the cold water to such fohn effect from the mountains an extent that dense fog is immedi- inland. During the summer of 1930 ately formed. Partly because of their there was not found a single instance greater initial warmth and moisture, either of marked southerly air move- and perhaps partly also because of ment or of a moisture distribution less wind and mechanical turbulence, indicative of Tp air at Seattle at the the dense fog appears almost immedi- ground. Probably this particular ately at the surface and grows deeper summer was quite typical of the with prolonged cooling. It is this average summer in this respect, so condition which gives to this region that it may be concluded that real its reputation for spring and sum- Tp air does not appear on the Pacific mer fogginess. These air masses of coast of the U. S. in summer, at Tropical origin, cooled in the Pa least at low levels. This can cer- source region, are designated on the tainly be said of Seattle. At San M. I. T. maps as Ntm. The symbol Diego the situation is much more Npa may appear on the summer uncertain, as the condition there is weather maps for Pa air which has normally one of comparative stagna- moved far south over warmer water, tion. Probably it would be somewhat or been brought to a considerable warmer and somewhat moister in distance inland. Excerpts. summer than in winter, corresponding to the higher temperature of the The Tropical Pacific Air Masses ocean surface in the source region. During the warm season the Tropi- On the California coast this air mass, cal Pacific air masses play a negli- if it appears at all, should be defi- gible role on the Pacific coast. It nitely cool at low levels and foggy, was remarked in the discussion of the because of the extreme local coldness Pp air masses in summer that the of the water along the coast. pressure distribution at this season It seems quite probable, however, along the entire middle and north that in the Plateau and Rocky Moun- Pacific coast of North America is such tain regions the Tm air is of real that there is found a persistent on- importance in summer. Tempera- shore gradient, and a correspondingly tures in the Plateau region are rather persistent movement of air at least high at this season, and the pressure to a considerable elevation from the normally rather low. Under these north and northwest. This pressure conditions rather steady southerly gradient may temporarily disappear winds frequently are observed in this to such an extent that the air move- region for rather prolonged periods, ment for a time is almost stagnant, with the result that the moisture thus the winds becoming light variable. brought inland establishes a specific At such times the aerological ascents humidity high enough so that con- at Seattle indicate the presence of siderable cloudiness and widespread higher temperatures at all levels, and thundershowers develop throughout usually of somewhat higher specific the low pressure trough. If the air humidity at the ground, than occur thus brought into the Plateau region in the Pp current when it is well had its source in the comparatively developed. But at upper levels one cool and dry Pp current prevailing usually finds a dryness indicative along the coast, an extremely low either of subsidence or of a light relative humidity would prevail in the TROPICAL AIR MASSES—SUMMER 105

air in this heated inland Plateau dity which more than anything else which is normally too dry to furnish characterizes our summer weather in much moisture by evaporation. We the eastern and central U. S. The have found that Pp air in summer map of July 26, 1930, 8 a.m. repre- is characterized by a specific humidity sents almost in ideal type form the on the order of 7 g at the ground, general condition which leads to the widespread decreasing to only slightly over 2 g prevalence of mT air in the U. S. in at 3 km elevation. Warm air which summer. We notice a weak trough of low reaches Ellendale from the northern pressure over the northern Plains states, and a broad Plateau low pressure region is ob- extension of the Bermuda High west- served to have a specific humidity of ward over the southeastern U. S. The from 10 to 12 g at 1 km elevation, resulting general air movement con- a value which definitely suggests that sists of a light flow from the West the is air of Tm origin. Recent Indies and Caribbean Sea northwest- studies, notably by Reed, of the upper ward into the Gulf of Mexico, thence winds in summer in the Southwest, northward over the southeastern and Indicate that this warm moist air south central U. S., and thence north- moves frequently at the upper levels eastward into the Lake Region and from the Tg source region via Mex- towards New England. In other ico. It is quite possible that it may words, we observe a slow steady flow come also from the Ts source region of Equatorial air which originated in

occasionally, btit apparently it is pre- the Trade-wind zone over the entire dominantly Tg air. eastern and central U. S. As this condition is usually very stationary, The Tropical Gulf, Tropical Atlantic the stream lines on this map as in- and Ts Air Masses dicated by the isobars may be taken For the Tg and Ta air masses the as typical trajectories of the mT air normal summer conditions are much masses in summer, the air masses more favorable than they are for the to which the following discussion Tp air masses. The combination of applies. the tendency toward the development The general difference between the of low pressure over the interior of normal winter and the normal sum- North America and the tendency mer condition as regards the distribu- toward the development of a well- tion and prevalence of the mT air marked center of high pressure over masses may be expressed in another the western Atlantic Ocean (Ber- way by saying that the zone of maxi- muda High) results much of the time mum frontal activity between the mT in summer in a pressure distribution and cP air masses, or the sub-Polar which brings mT air northward over front, is displaced in summer from most of the eastern U. S. and even its normal winter position somewhere into Canada. Consequently the mT over the northern Gulf of Mexico, air masses in the eastern and central northward into the U. S. almost to U. S. are present a much greater part the region of the Great Lakes. of the time and extend over much In general the properties of the wider areas in summer than they do mT (Tg and Ta) air masses in sum- in winter. They are responsible for mer as they leave their source region the oppressive heat vrith high humi- are similar to their properties in —

106 CHARACTERISTIC AIR MASS PROPERTIES

winter in the same region. The ocean time the values of w observed at Pen- surface temperatures during the sacola at all levels in the Tg air are warmest season average over the higher than those found at any other entire Gulf and Caribbean Sea region station. In spite of the high moist- close to 28° or 29 °C. In the Carib- ure content found at the 3 km level, bean Sea this is only 3°C warmer the excessive amount of water vapor than the temperature during the cold- present in this air mass at low levels est season, a difference which in- gives rise to a condition of marked creases probably to nearly 10 °C on potential instability. Up to the 3 km the immediate Gulf coast. Thus we level a decrease of 18° in ^E is should expect the mT air mass in noted, while the high value of w at summer to leave the source region this level would indicate that the somewhat warmer and somewhat decrease in $E should continue for moister than it does in winter, but at least 2 km further. This condition quite similar to its winter condition implies that all convective or me- in its general vertical structure. We chanical turbulence up to at least 5 should also expect to find that as the km elevation must effect an upward mT air mass passes inland from the transport of latent heat, and the high source region the general tendency of values of the relative humidity in- the effect of the continent will be dicate that very little vertical dis- towards a raising of the air mass placement is necessary in order to temperature, instead of towards a initiate active convection which lowering, as it is in winter. should extend well beyond this level. Pensacola, Fla., doubtless gives the This same marked potential instabi- best indication of the source proper- lity which we observe in the Tg air ties of Tg air in summer. We note masses coming from the Gulf of a surface temperature in the Tg air Mexico and the Caribbean Sea in which is almost identical with the summer, and which we shall find water surface temperature of the presently to be characteristic of all source region. Above the surface we maritime Equatorial air masses, is the find a moderate lapse-rate, about 0.6 source of the great amounts of of the dry adiabatic rate, which in- energy consumed in the genesis and dicates a condition of thermal sta- maintenance of the Tropical hurri- bility in the air mass. Afternoon cane. When we consider the added ascents would doubtless indicate a effect of insolational heating of the steeper lapse-rate near the ground. Tg air mass near the ground during The relative humidity is surprisingly the daytime as it moves inland from high, in view of the warmth of the the Gulf coast, it is obvious why Cu air mass, so that the specific humi- clouds which develop during the dity exceeds slightly the large value afternoon into Cunb and heavy local of 20 g. Probably this value is as thundershowers are so characteristic great as would be found as an of this air mass. Excerpts. [In average in any maritime location in Texas the invasion of summer Tg is typically shallow, with dry Equatorial regions. Not only is w Ts extremely high at the ground at Pen- air aloft above 1 or 2 km,, even less sacola, but the values found up to sometimes, which makes thunder- at least the 3 km level indicate very storms in Tg much less likely than high relative humidities at the pre- farther east; the decrease in aloft vailing temperatures. At the same indicates much potential instability — —

TROPICAL AIR MASSES SUMMER 107

but in the absence of much moisture aloft it is not realized except from marked vertical displacements with passage of occasional pronounced warm or cold fronts.* R. G. S.} O Modification of the Tg and Ta Air Is to Ntm O As the Tg air mass moves northward from the Gulf of Mexico in summer we should not expect as a rule any very great changes in its properties. During the late spring

and the summer the North American 0^ Continent is insolationally warmed even at rather high latitudes. Only in the region of the Great Lakes and off the north Atlantic coast is there any possibility of a marked cooling of the Tg air mass from the surface beneath. Apart from these water areas the ground is normally warmer, especially during the daytime, than is the water surface in the source region of the air mass, so that the general tendency must be towards a warming of the air mass from the warmer surface beneath as the Tg current "moves northward from the Gulf of Mexico. At greater distances from the source region we would expect to find a small decrease in the moisture content of the Tg air mass as the result of the precipitation of some of the excessive moisture in widely scattered thundershowers. Especially in the west and at upper levels we should expect to find the influence of the gradual infiltration and overrunning of dry Ts air from the upper levels of the sub-tropical anticyclones.* But in general, a condition of oppressive warmth and moisture with afternoon thunderstorms should characterize mT air over the entire eastern and central U. S. The temperatures at all levels tend to run a little higher than at *See discussion of Ts air in summer on

pp. 94-95 of this booklet ; and in the article on isentropic analysis by Mr. Namias, as well as in the note Showalter at the end of this section. Ed. . — — —

108 CHARACTERISTIC AIR MASS PROPERTIES the stability of the lowest km of the bility, and large diurnal tempera- air mass at the inland stations, the ture range stand in decided contrast consequence of nocturnal radiational to the humid, hazy, showery and cooling. The heating of the upper cumulus-laden Tm air; B. G. S.] strata of the air mass takes place In summer the modification of the during the afternoon thermal con- typical Tg or Ta air mass to the vection, but during the night the Ntm condition by cooling from below temperatures near the ground fall. occurs only in rather restricted re- Excerpts. gions, for over the continent proper [The highest temperatures aloft such cooling does not take place. It occur at Ellendale, farthest from the occurs only over a cold water surface. Gulf, and indicate the heating effect On the Canadian side of the Great of the continent to perhaps 5 or km Lakes this effect is sometimes notice- more. Stations all inland show lower able, especially in the early summer at all levels and, except in the w when the Lakes are still cold. At this southeast, where there is direct in- season the mT air from the south may vasion of Ta air, lower w at the arrive on the northern shores of the at Pensacola. ground, than North Great Lakes definitely cooled and from the Texas coast the Ts and Tg even foggy or with low St clouds. But layers become increasingly mixed by this cooling effect is most important diurnal convection, which lowers w over the cold water off the north and (9e at the surface and increases Atlantic coast. In only a day or two them aloft. Eastward of the western of slow movement of the warm moist plains the influence of air de- Ts mT air mass over this cold ocean sur- creases at the surface as continental face, the lower strata are cooled heating becomes less marked. As in almost to the water surface tempera- winter, it is difficult to distinguish Ta ture, and the cooling effect is carried and Tg air masses. upward, presumably by mechanical The pure or slightly modified Tm turbulence, with surprising swiftness. summer air in the southeastern The resulting condition is one of United States is so conditionally unstable stratification with the rapid stable and humid to well above 5 km consider- that thunderstorm convection is fre- formation of dense fog of quent; this becomes, as we have seen, able depth. This is the cause of the steadily less marked inland to the high frequency of summer fog on the north and especially westward, where north Atlantic coast. It is principally the dry and stable Tropical Superior in this region that the Ntm designa-

(Ts and modified Tg) air masses tion is used on the synoptic charts in with their clear skies, good visi- summer. Excerpt.

Major Frontal and Air Mass Zones of the Earth

Bergeron describes nine latitudinal Weather 5. The Stratus zone (with or without driz- Tories of each hemisphere as a function of zle) in the Stable Tropical Air at the Polar the large scale distribution of Air Masses and Front (or in the Polar Air at the Arctic Fronts*) (see Met. Zts., v. 47, p. 249, figs, Front*). 1, 6, and Ymer, hf. 2-3, 1937, p. 218, fig. 6. The first Cumulus zone of the Tropical 10):— Air in middle latitudes. 7. The Dry zone of diverging Tropical Air 1. The Stratus zone of the Stable Polar in the high pressure belt of the horse latitudes. Air (or Arctic Air*) in its source region. 8. The second Cumulus zone of the Tropical 2. The Shower zone of the tnoist-lahile Air: the trade-wind zone. Polar in Air (or Arctic Air*) somewhat 9. The Shower zone of the moist-labile Trop- lower latitudes. ical Air in the eauatorial region (the Dol- 3. The Dry zone of diverging Polar Air drums). (or Arctic Air*) underneath the Polar Front surface (or Arctic Front surface*). when there is also an Arctic Front pole- 4. The area of continuous precipitation wards of the Polar Front, five more Weather from Nimbostratus at the Polar Front (or Zones are arranged along the former front as Arctic Front* ) along the Polar front. AMERICAN AIR-MASS PROPERTIES 109

Further Studies of American Air-Mass Properties (Excerpts from Mon. Wea. Rev., July, 1939, pp. 204-217) Albert K. Showalter U. S. Weather Bureau, Washington, D. C. Winter Season

Continental Arctic Air: As shown teristic of cAw air near its source is by Willett and Wexler cA air is prob- still preserved and cAw - becoming - ably formerly maritime polar air cP'k is rare, except behind deepening (mPk) which is cooled by surface cyclones. As the polar air feeds into radiation forming cAw. A study of low latitudes it spreads out to occupy this air mass by Wexler has shown several times its original area and thus that there is a very sharp inversion the compensating subsidence shown by near the surface, and above, a lapse the various mean cross-sections and rate approaching the isothermal. tables of average properties [see Since the effect of surface cooling original article] is accounted for. rarely extends above 3 km above sea There seems to be considerable mois- level, the uncooled air above would ture added in the lower levels by sur- still be mP and very few observations face evaporation but because of the of cA air are available above that extreme stability of cAw and cPw air level. Occasionally cA air is mechan- it does not seem likely that the effects ically lifted to 4 km at Cheyenne and of surface addition of moisture extend in such a case it will be cooled adia- to any appreciable elevation. Consider batically and a temperature very low for example, the mean value of 2.2 for that height will result. Unstable g/kg for specific humidity with a po- Arctic air, cAk, sometimes occurs in tential temperature of 288° A at 2 km the Hudson Bay and the Great Lakes at Oklahoma City in cPw air. To regions but insufficient data are avail- establish an adiabatic lapse rate to able to include cAk air in this study. carry such a quantity of moisture up The change in designation from to 2 km by vertical convection,, a po- cAw to cPw has been more or less tential temperature of 288° A is re- arbitrary but usually one or two days quired at the surface. Since a surface elapse before cAw air is considered potential temperature of 288° A is cPw. A more definite criterion for the found only in air of very nearly trop- change in notation is the formation of ical properties it is evident that the a new Arctic front. Eventually the observed amount of moisture could not original polar air may become tropical have been carried up to that elevation air, so cPw merely marks the transi- by simple vertical convection. The tional stage. addition of moisture at higher levels in The striking thing in the movement modified polar air is probably best ex- of cAw - becoming - cP'w air into the plained by the principle of horizontal southern United States is that the mixing' along isentropic surfaces as steepening of the lapse rate which discussed by Rossby (see following would be expected from the addition art. on Isentropic Analysis).

of heat from below does not occur in Maritime Arctic Air, mA : —When an the mean, except in the lowest few outbreak of polar air moves over only hundred meters. Apparently subsi- a very small part of the Pacific Ocean dence proceeds so rapidly at all levels before reaching the United States it is above the shallow turbulent-convective usually designated as mAk. If its layer that the great stability charac- trajectory has been far to the south. 110 AIR MASS ANALYSIS

it usually is sufficiently modified to than the continent and shortly after t)e called mP. passing the coast line it should be Strictly speaking, for air masses labelled as a warm-type air mass ac- entering the United States, the nota- cording to the Bergeron classification. tion mAk should be reserved for Arctic Over snow covered areas mAk air very air masses which move directly south- rapidly assumes continental character- ward along the North Pacific coast and istics; thus we find the modified form have only a short trajectory over the of mA air sometimes colder near the ocean. The notations mPk and mPw surface than the original. are adequate to differentiate between Maritime Tropical Air, mT (Tm) : naaritime polar outbreaks having Since mT air is formed out of air which longer trajectories (see figure 1). The was originally polar, it shows a ten- unusual instability of mAk air, some dency for vertical stability with some vertical convec- flights indicating that subsiding action in the higher levels. has tion has obtained to at least 6 km, It will be noted that although the par- two important effects on its interaction tial-potential temperature of the dry the central with other air masses in air increases fairly rapidly with ele- and eastern part of the United States. vation, the equivalent-potential tem- Pirst, since often it is colder aloft than perature usually decreases with eleva- air sinking the surrounding masses, tion. This seems to indicate that at these levels, or subsidence, occurs from higher levels this air mass is relatively in mA and mP air. Second, and in- dry. Since mT air usually moves in- versely, this instability in same mA land with anticyclonic motion it may air is apt to cause an increasing ten- be assumed that the relative dryness dency for vertical divergence and in- aloft in mT air can be explained by creasing instability in air masses horizontal divergence with subsidence moving into a region occupied or re- in the upper levels of the subtropical air. In other cently occupied by mA anticyclonic cell. There is evidence words, the mA gains in stability while that some of the water vapor at higher the surrounding masses lose. levels must have been carried upward by vertical convection over scattered areas in the Gulf and Caribbean, and was diffused to the surroundings. The evident upward slope of the isentropic surfaces to the northward indicates that the moisture is carried aloft not only by vertical convection but also by isentropic mixing. The upward transport of moist air appears to occur near the edges of the subtropical anticyclones, while the subsiding dry tongues originate nearer to the 1X3 H S b i q to II II 13 centers.

Fig. 1. Average 0^ and Slopes of Character- Superior or Subsiding Air, S (Ts) ; istic Curves for the levels between 1000 and The notation Ts (Tropical superior) 1500 meters for American air masses, based was originally applied to air supposed on U. S. soundings of 1935-6. to have been derived from the upper During the winter months mA air subsiding portions of the subtropical near the surface is usually warmer anticyclonic cells. However, of recent AMERICAN AIR-MASS PROPERTIES 111

date the designation S has been applied move out from polar regions. to all warm air masses that show Modified moist Polar air, mPw relative humidities below 40%, which (Npm) : The mean values for these is taken as an indication of subsidence air masses show a tendency for and horizontal divergence. The study decreasing stability and increasing

indicates that most of the dryness moisture content. Although there is results from the subsidence of high- evidence that considerable heat and level air from a polar source. Isen- moisture are added by surface effects, tropic analyses have shown definitely there must be an addition of moisture that in winter a number of dry tongues aloft by isentropic mixing. Summer Season

Continental polar air, cA—becoming zontal mixing. It seems possible there- - - - cP (Pc becoming Npc) : The rate fore for a polar air mass with a purely of increase of moisture aloft seems continental history to attain in summer slightly in excess of that possible quantities of heat and moisture com- through vertical convection and it is parable to those obtained by an air necessary to believe that horizontal mass moving over the Caribbean Sea. mixing plays an important role. Maritime tropical air, mT (Tm) : It Maritime polar air, mA - becoming - appears that in general the potential - - mP (Pp becoming Npp) : The effects temperatures are higher in mT air of subsidence and outflow from the than in continental air masses and that upper portions of mP air seem to have therefore the air would move upward the the about same prominence as along the isentropic surfaces as it came effects of horizontal mixing so the over the land. Some of the cases mean values for mP air do not give studied indicate that at times a given positive evidence of the increase of isentropic surface may slope down- moisture aloft by isentropic mixing. ward from the Gulf to the continent. The notation cP or Np should be This means that portions of the mT used in cases of doubtful history of the column may at times move downward polar current, or in cases of overlap- in approaching the continent. It will ping layers of maritime and conti- be noted that mean potential-tempera- nental air having been thoroughly ture surfaces are approximately hori- mixed by vertical convection during zontal between Miami and Pensacola. the day or in some cases by mechanical Taking the vertical distance in turbulence. Since there is so little dif- meters between the 303° A and the ference in the properties of mP and cP 311° A surfaces as an inverse measure after 1 day's history over the continent of stability, one finds the mT air to be during the summer months, it would more stable in the mean than mPk air be wise to label all polar air masses but less stable than cPw air. This cP in the summer time, after they agrees with the statement made above have moved east of Spokane and south to the effect that mP air was likely to of the Canadian border. cause increasing instability in air

Modified moist polar air, mP (Npm) : masses moving into its territory. The The rapidly increasing moisture seems author is of the opinion that the to be a combination of the effects of greatest probability of rain occurs surface evaporation over water sur- when mT air replaces mA or mP, or faces or areas with abundant plant when mA or mP replace mT air. The life, coupled with the effects of hori- latter sequence is more conducive to 112 AIR MASS ANALYSIS precipitation during the colder sea- 40%, the source of this air can there- sons. fore be traced to subsiding polar or tropical air or to rapid daytime heat- Superior or subsiding air, (S) : The assumption that the dryness of this ing of either of those air masses. specific air mass is due to subsidence is not The range in humidity and necessarily always correct in summer, equivalent potential temperature is because rapid surface heating of rela- considerable at all elevations for the titvely dry air at that season may dry type of air called S, so it can be produce a deep column of air whose assumed from this evidence also that moisture content is far from the sa- the source of S air may be either turation values. When such an air polar or tropical or a stratification of mass is cooled during the night by air from both sources with a tendency surface radiation some slow sinking for horizontal mixing along the isen- may occur in the layers near the sur- tropic during the night and vertical face and those layers which are not convection during the day resulting cooled by radiation will show low rela- in a dissipation of the concentration tive humidities by the time of the of moisture. The orographic effect airplane observation the next day. also plays an important role in the Since S air is recognized only on the development of S air east of the basis of relative humidities less than Rocky Mountains. Air Mass Classification

Our study indicates that it is possi- fication is relative for any one day, ble to make some reasonable standard- and no definite limits of equivalent- ization of air mass classification for potential temperature have been in synoptic purposes but that any classi- use. This seems regrettable for sta- fication falls far short of definitely tistical purposes but in practical identifying the thermodynamic prop- synoptic work it can hardly be avoided. erties of the different air masses. In It is usually the practice to label the other words the mean values of each of air masses differently on either side of the various properties (see figs. 12 to a front, and since polar air is some- 15 of original article) show definite times modified very rapidly, it happens groupings for the different air masses, that modified polar air behind a cold and the individual values show definite front on one weather map may have a limits for the properties of fresh trop- higher equivalent-potential tempera- ical and fresh polar outbreaks. How- ture than a modified tropical current ever, the modifying influences affect- behind a warm front on a map a week ing air masses, especially in the later. Since all tropical air is polar summer months, result in a very wide air modified by surface effects, any range of equivalent-potential tempera- classification of air masses must be tures as indicated on the frequency only a compromise as to number of distribution charts (figs. 5 and 6 of types. The author is of the opinion original article). It can be seen from that no purpose is served by increasing a study of these charts that the classi- the number of types. The Air Mass Cycle

It is possible to identify from the air, one a moist cycle with rapid addi- mean seasonal properties for the dif- tion of moisture, the other a dry cycle ferent air masses, two distinct cycles with a marked subsidence and slow of transition from polar to tropical isentropic mixing in the early stages. —

AMERICAN AIR-MASS PROPERTIES 113

For the winter season the moist subsidence and surface heating with transitional stage (figure 8, original rapid increase of moisture by isen- article) from mP as represented at tropic mixing. Appreciable quantities Dayton, to Tm at Pensacola and St. of heat and moisture may be added to Thomas, Virgin Islands, shows con- mT air over the continental United tinual subsidence and increasing mois- States. Thus the highest value of ture. The persistent stability through- equivalent potential temperature, 366° out the transitional process, the A, observed during this study was difference in potential temperature found at 1,000 m at Dayton on August between 500 m and 5,000 m remaining 22, 1936! practically constant from the mA to The dry cycle in summer represents the Tm stage, indicates that the prin- rapid modification of the polar air cipal addition of moisture must occur masses with subsidence aloft and slow by means of mixing along isentropic addition of moisture by isentropic surfaces, with some probability of con- mixing over the continent, then convection in the final mT stage. tinued heating accompanied by vertical The dry winter cycle (fig. 9 of orig- convection and convergence over the inal article) shows rapid subsidence Gulf and Caribbean, followed by a with slight increase of moisture by slow spreading out and subsidence as isentropic mixing from the mA to the the air assumes an anticyclonic trajec- S stage. When this air mass moves to tory on its return from the lower lower latitudes the subsidence de- Caribbean to El Paso. From El Paso creases, rapid surface heating develops to the Mississippi Valley there is ap- and the S air begins to mix both verti- parently a continued addition of heat cally and horizontally with mT air. and moisture and the mT air again The vertical mixing is probably con- becomes convectively unstable over the fined to the lowest layers affected by Mississippi and Ohio Valleys. daytime convection and most of the In view of recent discoveries of the increase in moisture aloft appears to meteorological significance of isen- be due to isentropic mixing. tropic charts it is further recommended The identification of the moist and that more attention be given to the dry cycles is more difficult in the sum- slope of potential temperature sur- mer season because of the greater faces in situations free from condensa- tendency for vertical convection during tion. Allowance should be made for the the day, with convection occurring effects of horizontal mixing along under saturated conditions which can- isentropic surfaces and unless the isen- not be analyzed by charts using poten- tropic surfaces in one air mass actually tial temperature surfaces. However, intersect the ground or at least show the mean values, indicating unsat- a sudden increase in slope, the synoptic urated conditions, suggest for the analyst should label the air masses moist cycle conditions similar to those differently with caution.— (Excerpts.) observed in the winter season, namely.

Illustrations The following collection of weather maps and cross sections selected from articles published in the Bulletin op the American Meteorological Society is reprinted to offer examples of frontal and air-mass-analyzed weather situations, though the technique of presentation used is not altogether conventional. But they will give those who have no access to other publications nor to MS analyzed maps of a meteorological service or institute, some idea of interpretations of atmospheric structure and movements that can be or are made by experienced map analysts. Ed. 114 AIR MASS ANALYSIS A Dust Storm May 9 to 11, 1934, a famous duststorm raced from Montana and North Dakota to the Atlantic Seaboard and out to sea, one of the few such to reach the ocean. The maps for this situation, below, were analyzed and discussed by G. R. Parkinson (Bull., May, 1936, pp. 127-35.) The dust storm generally rages in Npp air, which is unstable (by day at least) and windy in the winter and spring. Note how in this case the dust (stippled areas) was raised in the foreward part of Npp air masses where the pressure gradient was steep and hence the wind fairly high and the iapse-rate unstable, and in passing over regions of barren soil due to drought, plowing and winter; once raised to considerable heights in the air mass, the dust stayed in suspension long enough to be carried still higher and a long ways East.

(A). Weather Map, 8 a.m.. May 9, 1934.

(B). Weather Map, 8 p.m., May 9, 1934. ILLUSTRATIONS 115

*>.* »•• Jo»«1Hi„, «',»?!(., _2M 29 3

(C). Weather Map, 8 a.m., May 10, 1934.

(D). Weather Map, 8 p. m.. May 10, 1934. 116 AIR MASS ANALYSIS

Flood Rains

PENSACOLA _\

Location of fronts at the surface at 7:00 a. m., C.S.T., Sept. 27, 1936, WITH DIAGRAMS OF THE CHARACTERISTIC PROPERTIES OF THE AIR MASSES ACCORD- ING TO THE AIRPLANE SOUNDINGS OF EARLY THE 27TH, (E.S.T.). (Solid lines are cold fronts, dashed lines warm fronts, dotted lines occluded fronts. The graphs show temperature in °C, dv., and specific humidity, plotted against height in km above sea level, with air mass" types, cloud layers, winds and (cont., next page) ILLUSTRATIONS 117

relative humidities written in figures at the sides; winds are for the 6 a.m. C.S.T. pilot-balloon runs. The Montgomery sounding is inserted for reference.) This unconventional diagram by E. J. Minser (Jan. Bull., 1938, p. 34) gives an interesting display of upper-air data, most of the surface data being omitted to avoid confusion. The situation was one in which very heavy rains fell in eastern Texas, Oklahoma and Mo. as the Pc and Npc cold fronts slowly squeezed (occluded) the moist Tg sector ahead of them. 118 AIR MASS ANALYSIS

Fronts and Aircraft Icing

Cold Fronts.—This (Fig. 6) and the following cross-sections (Figs. 7-9) through fronts are based on the synoptic experience of analysts working for a large air line (T.W.A.), and are taken from a paper on situations for icing of aircraft by E. J. Minser (Bull., March, 1938, pp. 118-121), with his kind permission. These meteorologists obtain radioed reports from the pilots as they fly along, and thus acquire an unusually detailed knowledge of actual cloud and upper-air structures. Fig. 6 is semi-schematic but vividly illustrates what happens just ahead of an advancing cold front (Pc into Npc) in a mountainous region: clouds with snow squalls (this is winter) over each range. Note the freezing-line (dashed), the frontal precipitation (first rain, then snow), and the surface map at left. (Temp, in °F, heights in thousands of feet, in this and following figures.) ILLUSTRATIONS 119

COLD FRONT

I2000--

FlG. 7 is generalized cross-section from Columbus, O., (CO) to Newark (NK), showing a typical cold front with aircraft icing conditions in its clouds. The dashed-dot lines show how a pilot must fly to avoid the worst ice forming dangers. Snow squalls in the mountains are probably from both the colder and warmer air. (The windward sides of the mountains are more apt to be fogged in with clouds under such conditions than clear as shown here.) 120 AIR MASS ANALYSIS

COLD FRONT

WY r S^OOAMC-DECEMBERS. 1937 SCALE IN MILES

Fig. 8 is from actual reports of pilots flying between Albuquerque and Kansas City in the morning of Dec. 8, 1937. A Pc cold front is advancing westward and lifting the Npc air over it and over the mountains. Snow squalls (indicated by crosses). ILLUSTRATIONS 121

COLD FRONT

2 /

MQ WT CG ML GO AO TL VK C\

930 PMC -DECEMBER 7,1937

Fig. 9 is the actual section from Kansas City through Chicago to Cleveland based on a pilot's flight at night. There is a cold-front-type occlusion with the warmest air-mass entirely aloft here, causing snow to fall over a wide area. 122 AIR MASS ANALYSIS

Bergeron's Model of the Warm-Front-Type Occlusion (Characteristic of Western Europe, Western North and South America, temperate zones)

^'^Tor^-^^ ^00^ ,Jl " " 6£M__ ^ — ^2.T^ 1000c. 60°

_ StratosTDheTe

to c^jlj^-vt^-^->v^^,~^^

mo :

ILLUSTRATIONS 123

Legends for Model op the Warm-Front-Type Occlusion

On the map:— In the vertical sections — Cumulus •^—^— Surface of Polar Front or of Tropopause Showers """""— Internal Frontal Surface "Upslide" Bain Occluded Frontal Surface ^ Stream-lines referred to a system moving with Limit of Ast 10/10 the occlusion

I consisting I Cloud-mass of Warm-sector Rain M I M ice-crystals ^^^^S^ Cloud-mass consisting of water-droplets Drizzle Lower limit of ice nuclei Stratus or Fog

III ill 11 II Ordinary precipitation Warm Front Vc::A-:'/SV Drizzle Cold Front Warm air woo- Isobar

+-Z Isallobar In the high pressure wedges: Limit of Cist { Along the fronts: Limit of drizzle PL = Polar Air. TL = Tropical Air

Characteristic Points op the Occlusion Model Indicated in Fig. 4,

Vertical Section A : ai = Rear limit of Ast, attached to the recurving Occlusion 3,2 = Rear limit of Nbst, attached to the recurving Occlusion as = Upper retrograde Cold Front, becoming Warm Front a4 = Upper progressive Cold Front as = Fore limit of Nbst attached to the original Occlusion a,e = Fore limit of Ast attached to the original Occlusion ar = Fore limit of Cist attached to the original Occlusion

Vertical Section B: bi = Rear limit of Ast attached to the recurved Warm Front, now Cold Front b2 = Recurved Warm Front at the ground, now Cold Front bs = Fore limit of Nbst, attached to the recurved Warm Front, now Cold Front b4 = Occluded progressive Warm Front at the ground bs = Fore limit of the new Upslide Cloud System, formed on the occluded Warm Front be = Rear limit of the old Upslide Cloud System, formed on the original Warm Front and modified by the Upper Cold Ftont br = Upper progressive Cold Front bs = Fore limit of Nbst formed on the original progressive Warm Front Surface bg = Fore limit of Ast formed on the original progressive Warm Front Surface bio = Fore limit of Cist formed' on the original progressive Warm Front Surface

Vertical Section C:

Ci = Fore limit of Cist of the next disturbance C2 = Rear limit of Acu opaoiis attached to the secondary Cold Front Cs == Induced secondary Cold Front C4 = Fore limit of Nbst formed by the secondary Cold Front (Continued on next page) 124 Am MASS ANALYSIS

Cs = Rear limit of Acu opacus attached to the primary Cold Front Ce = Occlusion Point Ct = Fore limit of Nbst formed on the primary Warm Front Surface Cs = Fore limit of Ast formed on the primary Warm Front Surface Cg = Fore limit of Cist formed on the primary Warm Front Surface

Vertical Section D: di = Fore limit of Ast of the next disturbance da = Rear limit of Acu opacus attached to the wave disturbance of the Cold Front ds = Cold Front of the wave disturbance on the primary Cold Front d4 = Warm Front of the wave disturbance on the primary Cold Front ds = Fore limit of Nbst on the Warm Front Surface of the wave disturbance de = Rear limit of Nbst formed on the primary Cold Front Surface di = Primary Cold Front ds = Limit of drizzle before the primary Cold Front dg = Limit of drizzle behind the primary Warm Front dio = Primary Warm Front dii = Limit of drizzle (= rear limit of Nbst) before the primary Warm Front di2 = Fore limit of Nbst formed on the primary Warm Front Surface

(ij3 = Fore limit of Ast formed on the primary Warm Front Surface di4 = Fore limit of Cist formed on the primary Warm Front Surface

A Three-Dimensional Picture of the Warm- front Occlusion (L ^ low pressure center

at the ground ; L' := low pressure center

in the warm air aloft ; P =^ the point where the upper cold front pierces the X, z-plane). ILLUSTRATIONS 125

Spring Showers

Air mass and weather sequence passing over Washington, D. C, May 6-7, 1935.—A time-line cross-section in which the earliest hour is at the right. This unusual diagram was made up from a study of the surface observations and the synoptic cross-sections at the Weather Bureau in Washington for the purpose of summarizing the climate of the whole month in terms of air masses and fronts. However, it incidentally also shows an interesting typical sequence in the upper air. Note the showery rain (stippled bars) from the Tg being occluded and lifted between Np and older Np; and the location of Ts, which is characteristic—the rain stops abruptly when it arrives. The pressure and temperature traces at the ground are typical. There was a thundershower at the cold front. The Tg sector is of course cloudy, the Ts/Np zone nearly clear. (From: Botts, Sept., 1937, Bull. p. 290-297.)

ds 126 AIR MASS ANALYSIS

Winter Cyclone with Dust Storm (From: Parkinson, Bulletin, May, 1936, p. 130-1)

Fig. 1. Weather Map, 8 a.m (75th Merid. Time) January 16, 1935. (Solid lines=cold fronts, dashed lines=warm fronts, dotted lines=occluded fronts, stippling=duststorm areas.)

[V n»JWa>J litrtTis ^

Fig. 2. Weather Map, 12 Noon, January 16, 1935. ILLUSTRATIONS 127

Fig. 3. Weather Map, 4 p. m., January 16, 1935.

Fig. 4. Weather Map, 8 p.m., January 16, 1935. 128 AIR MASS ANALYSIS

Maps and Cross Sections of Fronts: Aircraft Icing (From E. J. Minser, Bulletin, May 1935, p. 132)

< —

ILLUSTRATIONS 129

A Succession of Polar Air Masses: Weather Maps and Cross-Sections for Nov. 30-Dec. 2, 1938 The charts below are from an ar- Washington show the considerable ticle by George and Elliot in the Bull. depth of the P? compared to the Pc Amer. Met. Soc. for March 1939. The air and the tendency for warm-front- period was featured by an outbreak type occlusions and upper cold-fronts of Pc air over the Great Lakes region, to form from Pp invasions. (Cold and a series of rapidly moving in- fronts are drawn solid black, warm vasions of Npp air across the western fronts double lined, occluded fronts states. Npc is stagnating in the dashed, upper fronts dotted; tempera- Southeast, and a tongue of Ta begins ture in °F and winds are entered for to move over Texas from the Gulf. a few stations). R. G. S. The cross-sections from Oakland to

Nov50

Fig. 1. Synoptic Chart, Nov. 30, 1938, 7:10 a.m., E. S. T.

30. 1358 Nov Dec I. 1933 Fig. 2. Cross-section, Oakland to "Washing- Fig. 4. Cross- section, 4:00 a.m., Dec. 1,1938. ton, 4 a.m., E. S. T., Nov. 30, 3938. 130 AIR MASS ANALYSIS

Dec I

Fig. 3. Synoptic Chart for Dec. 1, 1938, 7:10 a.m., E. S. T. 7

v^^^/

HIGH

Dec 2

Fig. 5. Synoptic Chart for 7:10 a.m., E. S. T., Dec. 2, 1938. ILLUSTRATIONS 131

Dec I. 1938

Fig. 6. Cross-section for 4:00 a.m., E. S. T., Dec. 2, 1938. A Rossby Diagram

A Rossby diagram of an Airplane Sounding at Nanking, China, Aug. 23, 1937. There is a shallow layer of Tm air at the surface with a sharp front at 706 meters, above which Equatorial marine air exists to the top of the sounding. This sounding was made just after a typhoon passed inland over Nanking, the warmer Em being imported aloft by the circulation of the storm. (From a paper by Tu, Bull. Amer. Met. Soc, March, 1939.)

Synoptic Charts Showing Wintar Cyclones (Figs. 1, 2, 6-13 from: Dorsey, Bull. Amer. Met. Soc, Oct. 1938.)

08 09 10 II II "Q-^'o^ lOa

Feb. 25,1933-8

Fig. 1. Deep cold air over New England was augmented by fresh Fc the next day. The warm and occluded fronts in the low over Michigan are producing snow (stippled area) over a wide region and caused heavy snow in New England later the same day as it moved eastward. 132 AIR MASS ANALYSIS ILLUSTRATIONS 133

Fig. 4 shows the sudden intensification of the coastal storm and the subsequent movement of the Pc air mass shown in Fig. 3.

Fig. 5 is a W-E cross-section of the air masses over southeastern New England and just north of the cyclone center at 8.00 a.m. the 20th, showing the occlusion of Tg air causing heavy snowfall around New Haven due to lifting of the To, but only light snow at Fall River where the Tg is not being lifted much (see Fig. 4). 134 AIR MASS ANALYSIS

0.4 0.3 0? 01 0.0 Jan. 22.'l935-eA/-

Fig. 6. The N-S alignment of the Pc cold Fig. 8. front results when cold air passes rapidly south to the Gulf while the tropical air is not displaced eastward very far. A wave-disturbance has started in the southeast and an older one is occluding over New Brunswick. The western low joined with the southeastern one the next day and then moved NE-ward with the Tm air spreading westward aloft over the Pc causing very heavy snow and N-ly gales in New England. (Legend for this and Figs 7-13 same as in Fig. 1.)

Fig. 9. Figs. 7, 8. and 9. A succession of weak occlusions and young wave disturbances along a quasistationary cold front, the last wave deepening and occluding into an intense cyclone with heavy snow and gales over the Fig. 7. northeast. ILLUSTRATIONS 135

April 12. 1933-S

Fig. 10- A somewhat complicated situation Fig. 12. The deep occlusion in Canada had accompanied by widespread precipitation. The been formed by Tg intensifying an older occlu- three occluded lows resulted from a series of sion that had advanced from the Pacific along minor wave disturbances that came in from a Pc front to near Omaha. The Pc spread the Pacific. The southern low deepened fur- south behind the low to California and by ther and occluded off Hatteras, causing heavy the 12th was as shown here modified to Npc snow in Boston on the 14th. with a fresh Pc outbreak in the NW. A secondary low, in the southeast, formed at the base of the occlusion. It moved NE between rising pressure at Bermuda and the Pa current flowing down from the N, occluding off the New England coast where it caused Nly gales and snow. The northern low is one of the spring type that sometimes develop into deep cold vortices without fronts—"dynamic lows".

Fig. 11. A large occluding Pacific low moving eastward along the western Pc front eventually drew Tg into its circulation causing intensification and a new wave which was occluding the next day over New England. Note the upper cold front (warm-front occlu- Fig. 13. This shows a typical situation for sion) in the west where the Pp-Pc occluded Pa invasion of the northeastern seaboard, in- front (Npc occluded) is moving aloft over duced by a slow moving high to the north and the Pc. The Tg wDl soon enter into this an occluding wave disturbance from the south- upper occlusion by rising over the Npc and east. As the low moves NE, the Pa may con- displacing it. tinue for days on the seaboard. 136 AIR MASS ANAX.YSIS

X. ISENTROPIG ANALYSIS * Jerome Namias Introduction frontal analysis tine of analysis and forecasting. The IN AIR MASS and use is made of "indirect aerology" current practice is all too often to —a technique of deducing chiefly carry out an analysis of surface from observations of clouds and hy- weather maps, afterwards using the drometeors the nature and structure upper-air data merely as a check. of the atmosphere above the ground. This form of treatment, it hardly need This method supplies a good deal of be stated, rarely leads to the develop- information essential to weather anal- ment of new and directly usable ideas ysis and forecasting, and is especially for interpreting the soundings. valuable w^here direct observations of Appreciable progress in the use of the upper air are lacking. Where a upper-air data has recently been made fairly dense network of upper-air by Rossby and his colleagues [3]^ at soundings is available, however, in- the Massachusetts Institute of Tech- direct aerology naturally must give nology; their technique, called isen- way to the consideration of observed tropic analysis, goes further than conditions. In the United States we merely supplementing the surface are fortunate in being able to make analysis of air masses and fronts; it use each day of some thirty radio- brings to light much entirely new sonde observations, and it appears knowledge of the physical processes that this number will increase from at work in the atmosphere. Isentropic time to time. Indirect aerology is analysis has already become an in- thus being forced more and more into tegral part of the modern forecaster's the background; but there arises the technique, and is now widely used in problem of how to use effectively the United States. these upper-air data in the daily rou-

§ 1. Basis for THE Analysis In Articles II to IV we discussed the the "characteristic" curve. This curve need in synoptic meteorology for con- is unaltered during any adiabatic servative elements by means of which process involving the same particles, parcels of air may be identified from for in this case the individual points day to day. It was pointed out that of the curve stay fixed. Thus the two of the most conservative of these characteristic curve may be used to elements are potential temperature identify vertical air columns as they and mixing ratio or specific humidity, move over the surface of the earth. both of which do not change during Under the assumption made above, adiabatic processes as long as the air each potential temperature in a series remains unsaturated, and as long as of characteristic curves obtained at turbulent redistribution of heat and different stages in the history of a moisture may be neglected. These moving air column will then be char- two quantities are used as coordinates acterized by a practically unchang- of the Rossby-diagram [1]^, and if the *Reproduced, with changes, from the MS points of an aerological sounding are of the chapter under the same title which ap- plotted on such a diagram we obtain pears in the book "Weather Analysis and Forecasting," by kind permission of Prof. Sverre Peterssen and the McGraw-Hill Book ^See references at end of this chapter. Company. ISENTROPIC ANALYSIS 137

ing mixing ratio. We may therefore derations, the fruit of later studies, choose some particular surface of helped to indicate that isentropic sur- potential temperature and use the faces should be used. mixing ratio on this surface as an In a study of the Gulf Stream, identifying element by means of which Rossby [5] found much evidence of parcels of adiabatically moving air large-scale cross-current mixing be- having the chosen potential tempera- tween the Gulf Stream water and its ture may be traced from day to day. environment, and that this mixing The equation (see Article VIII) takes place along surfaces of constant where S = Cv log + constant density". In the atmosphere, expresses the fact that a surface of compressibility must be taken into ac- it is readily seen that this type constant potential temperature is also count, chiefly along a surface of constant entropy, and of mixing must operate isentropic surfaces. In figure 1, for hereafter we shall speak of it as an have a nonnal atmos- isentropic surface. Since the atmos- example, we pheric stratification in which the po- phere is normally stable, the potential temperature increases steadily with elevation. We may then consider the atmosphere as consisting of an infi- nite number of thin isentropic sheets limited by the surfaces = constant,

-{- do = constant, etc., etc. The above considerations, in part, led Rossby [2, 3] to suggest that upper-air charts be drawn along isentropic surfaces, rather than along

constant levels where the comparison Fig. 1. Forces Resisting Displacements Isentropic Sheets. of elements from point to point is at FROM times misleading because of ascending tential temperature increases with and descending motion of the air elevation. A parcel of air originally through these level surfaces. Sir resting at A, if displaced to the point Napier Shaw [4] had suggested some B, will be subjected to a downward years ago that weather maps be force Fi, since it finds itself colder drawn along isentropic surfaces, and than its environment (see Art. II). had actually constructed a few such Similarly, if the parcel is displaced to charts containing isotherms. He C a force F2 resists the displacement. pointed out that isotherms on an isen- These restoring forces are propor- tropic surface were also lines of tional to the vertical gradient of constant density and constant pres- potential temperature. But if A is sure. But Shaw did not make use of displaced to D, that is, along an isen- the mixing ratio (w) as a second tropic surface, there is no resisting identifying element to be used on isen- force, since at each point the particle tropic charts. For numerous rea- has the same temperature and density sons, probably the main one being the as its environment. Thus lateral mix- lack of aerological data at the time, ing in the atmosphere must take place Shaw's suggestion was not put into chiefly along the surfaces of constant practice, and the method of analyzing potential temperature (isentropes). conditions along isentropic surfaces In saturated air the mixing operates lay dormant until revived by Rossby ^Strictly speaking, surfaces of constant po- several years later. But other consi- tential density. 138 AIR MASS ANALYSIS chiefly along surfaces of constant equivalent-potential temperature. NORTH There is also some evidence in support of the view that the intensity of vertical mixing decreases and the intensity of lateral mixing increases as the vertical stability increases. This latter conclusion is known as Parr's principle [6]. The importance of isentropic mixing in the atmosphere lies in the fact appreciable magnitude, that if it is of WEST EAST this mixing must lead to sizable shearing stresses operating across planes normal to the isentropic surfaces, whenever there are variations in wind velocity in a broad current flowing along the isentropic surface. If a westerly current flowing along an isentropic surface is of such character that the velocities are larger to the north and diminish to the south, SOUTH shearing stresses will tend to speed up the westerlies to the south and Fig. 2. —Accelerating and retarding forces retard the eastward flow along the operating on an isentropic current profile in which velocity varies in neighboring fila- northern edge of the current. In other ments. words, the shearing stresses tend to account of lateral mixing within a uniformly over distribute momentum broad westerly current whose velocity all filaments of the current. As a profile is indicated by the curve. The of these stresses, frictional result motions which result from the Cori- volume forces are set up which act in olis force are given by the arrows the direction of the axis of the cur- marked v. rent, retarding in the regions of It will be seen from Fig. 2 that air velocity maxima, accelerating in the motions created by shearing stresses regions of velocity minima. Under may result in regions of convergence conditions these axial steady state and divergence. For example, at P forces must be balanced by Coriolis air is being flung to the south, while forces associated with slight motions at it is being flung to the North, normal to the current axes. Thus, as so that between these two filaments pointed out by Ekman [7], in the divergence must set in. Similarly, Northern Hemisphere an accelerating- convergence must set in in the region force F, per unit mass, acting east- between O and Q. At the ground in southward motion ward, produces a regions above which convergence of whose velocity is this nature is taking place at all lev- F rises, while below re- V = els the pressure

2 (0 sin cji gions of divergence the surface pres- Fig. 2 shows diagrammatically the sure falls. Far to the right of the accelerating and retarding forces Fa stream the lateral shearing stresses and Fr, respectively, which operate on will also produce convergence, for to :

ISENTROPIC ANALYSIS 139 the extreme south the velocities are and Proctor for diffusion over small hardly accelerated at all. Therefore, distances and those obtained by it is highly probable that lateral Defant by considering cyclones and shearing stresses may be important in anticyclones as large-scale turbulent -producing cross-isobar wind compo- elements in the general circulation. nents, and thus also pressure varia- The analysis of isentropic charts has tions which are of a purely dynamic shown that eddies of appreciably rather than thermal-adveetive nature. smaller size than extra-tropical cy- There has been accumulated an in- clones and anticyclones occur almost creasing mass of evidence, both on daily in the isentropic flow patterns. theoretical and observational grounds, There is being gathered an increas- that the magnitude of these lateral ing mass of observational evidence to shearing stresses is sufficient to ac- substantiate the theory summarized count for such pressure variations. above^ In the following pages we Thus by equating isentropic shearing shall briefly discuss the practical re- stress within sloping parallel isen- sults of studies of some of this ma- tropic surfaces which intersect the terial. ground at a normal angle and stress Before proceeding with this discus- due to ground friction (and assigning sion it is well to repeat that the isen- reasonable values of lapse rate and tropic analysis suggests itself as a wind velocity in temperate latitudes) practical tool in synoptic meteorology Rossby [8] obtained a lateral stress for the following two reasons of 167 dynes/cm' corresponding to an 1. It provides a method of identify- isentropic shear of 2.5 X lO-'^ sec-^ ing and following large-scale moist and an isentropic eddy viscosity of and dry currents and of anticipating 6.7 X 10'' grams/cm/sec. These val- their subsequent thermodynamic modi- ues agree fairly well in order of mag- fications. nitude with those obtained from a 2. It provides a method for taking study of the diffusion of water vapor into consideration lateral shearing actually observed in isentropic charts stresses and their hydrodynamical

(Grimminger [9]) ; moreover, they lie effects on the prevailing flow pattern. between those found by Richardson

§ 2. Plotting Routine The mechanical operation of pre- ution. Thus the isentropic surface paring upper-air data in a form suit- = 290° which has been found useful able for isentropic analysis is quite in the United States during the win- simple. We require for the analysis ter months is far too low during the two sets of upper-air charts: isen- summer months. In general, the isentropic charts, for which an ordinary tropic sheet finally chosen should be geographical base map suffices, and high enough to be above the layer in- atmospheric cross sections which repre- fluenced by surface friction, and a*" sent vertical planes cutting through the same time, low enough to show a the atmosphere along desired lines. The large range of specific-humidity val- choice of some convenient isentropic ues. It is obvious that over a large surface or surfaces for analysis must area of diverse topographical and then be made. The deciding factor in climatic features these two criteria this regard is the general elevation of the surface, which again depends ^A complete quantitative treatment of the underlying theory is at present in prepara- upon the general temperature distrib- tion by C.-G. Rossby and his colleagues. 140 AIP. MASS ANALYSIS cannot be completely satisfied. How- pheric pressure\ The appropriate ever, it is in general possible to find values for plotting on the isentropic an isentropic surface that satisfies chart are readily extracted from aero- these conditions well enough for a logical soundings with the help of reasonably sound analysis. some convenient thermodynamic dia- In North America suitable values gram (see Article III). The pilot-bal- of potential temperature for the in- loon wind observations are then en- dividual seasons are: tered along the isentropic surface for Season Potential Ternperature those stations where the height (or Winter 290°-295°A pressure) of the isentropic surface is Spring 295°-300°A already evaluated. In addition to the Summer 310°-315°A above data, it is helpful to indicate Fall 300°-305°A the form and motion of clouds as well The abrupt increase from spring to as hydrometeors observed at the aero- summer values is due to the normally logical sounding stations together rapid increase of free air tempera- with the levels in which these phe- tures as summer convection sets in. nomena are reported. During periods of unusual weather The atmospheric cross-section dia- it is sometimes necessary to change grams now in use in United States to a different surface for a few days, have pressure (on a logarithmic scale, and then to return to the normal for but p"''^^ scale is being introduced) the season. It should be pointed out, as ordinate and horizontal distance as liowever, that such changes carry abscissa. The values of mixing ratio ivith them a certain loss of contin- and potential temperature are plotted uity—and it cannot be emphasized too at the significant levels for each sta- strongly that continuity is the prim- tion. If time permits it is convenient ary requirement of isentropic anal- to plot also the relative humidity and ysis. For this reason it is most ad- the temperature. By constructing lines vantageous to follow from day to day of constant moisture and constant po- the flow patterns in a given isentropic tential temperature in the cross sec- surface, and when an abnormal period tions we obtain a picture of the mois- suggests change of surface, to con- ture and temperature distribution struct an additional set of charts for along the vertical plane represented a more representative surface for this by the cross section, as well as a view particular period. of the moisture pattern in the isen- The elements plotted along the isentropic surfaces. Pilot-balloon wind tropic surface are the mixing ratio, observations, clouds and hydrometeors saturation mixing ratio, and atmos- are also plotted in the cross sections.

§ 3. Technique OF Analysis In order to enter all available pi- Contour lines may be drawn more ac- lot-balloon winds on the isentropic curately by taking into consideration surface it is necessary to sketch a set the guiding factors mentioned below. of lines of constant pressure. We It is, indeed, necessary to make use of shall refer to these as contour lines. these aids when one wishes to extend Usually it suffices to draw such lines the analysis into regions in which the for each 50th millibar. The number data are sparse. of aerological soundings is in general *Byers [10] has developed the use of con- instead of mixing ratio, insufficient for drawing the contour densation pressure _ and that method has been adopted in the lines in a purely mechanical fashion. U. S. Weather Bureau. :

ISENTROPIC ANALYSIS 141

The particular isentropic surface or about the structure and pattern of surfaces to be analyzed may be the contour lines. Regions in the sketched immediately in the cross vicinity of well marked fronts are sections, and the positions of troughs characterized by a crowding of the or ridges may thus be determined and contour lines. Since cold fronts are indicated on the isentropic map.* In generally much sharper and steeper sketching the isentropes on the cross than warm fronts, this steep gradient sections, one should bear in mind that of contour lines on the isentropic in the case of adiabatic lapse rates, chart is usually at its maximum just (i.e., d0/dz = O) the isentropes run behind cold fronts. Moreover, as is vertically. In general, one can deter- to be expected, the contour lines usu- mine the lapse rate directly from the ally run parallel to the surface fronts. isentropes by making use of the fol- Experience shows that most well-de- lowing simple derivation. As an ap- fined fronts are characterized by con- proximation we may write: stant, or almost constant, potential temperature, so that the frontal sur- where T is the temperature and z the faces have a marked tendency to height above sea level expressed in coincide with the isentropic surfaces. hundreds of meters. Differentiating Moreover, since a frontal surface is with respect to elevation we obtain characterized by stable stratification, de 'dT dT de = + 1, or = 1. would have a maximum within d z d z 'd z d z dz If one chooses for dz a unit dis- the transition zone. Since lateral mix- dT ing occurs mainly along isentropic tance, say 1000 m, then , is the surfaces, it follows that frontal sur- 3 z faces which are parallel to isentropic lapse rate, determined by simply noting surfaces will not be destroyed by the difference of potential tempera- mixing. On the other hand, frontal ture in the vertical range; or the dis- surfaces which intersect the isentropic tance between two successive isen- dT surfaces will dissolve on account of tropes may be estimated, and lateral mixing, unless the front is 3 z situated in a field of motion which is quickly determined. This method is pronouncedly frontogenetical. When especially helpful when lapse-rate dia- the front is associated with large grams are not at hand. areas of precipitation, the process is The domes and ridges in the isen- no longer isentropic, and lateral mix- tropic surfaces are found in regions ing does not take place along isen- the occupied by cold air masses, and tropes, but along surfaces of con- troughs in the isentropic surfaces are stant equivalent-potential tempera- in the found the warm air masses. To ture or surfaces of constant saturated extent that the surface pressure potential wet bulb temperature. In changes are due to advection of cold such cases the isentropic surfaces will and warm masses, the slope of the cross the frontal surfaces. At cold isentropic surfaces will be greatest fronts, however, the area of precipita- above the isallobaric maxima. tion is normally relatively narrow so Fronts on the surface weather map that, in most cases, cold fronts lie also offer a great deal of information along isentropic surfaces above the

*Prof. Spilhaus has suggested a more re- frictional layer. The warmest air is fined technique for drawing the isentropes {Bulletin Amer. Met. Soc, June, 1940). normally found just ahead of the sur- 142 AIR MASS ANALYSIS face cold front. Thus the trough in formed fronts are a result rather than the contour lines is usually found a cause of the processes in the upper slightly in advance of the cold front, air. It thus appears that many fronts with a steep upward slope of the isen- on the surface weather map are in- tropic surface in the rear of the cold duced by action taking place first in front. the upper air and later showing up at The parallelism of contour lines the ground. This, obviously, means with well-marked cold fronts many that a frontogenetical wind-field de- times enables one to construct height velops aloft and gradually extends lines in regions where upper-air ob- downwards. servations are sparse. The applica- The above ideas are illustrated in tion of this principle to frontal-wave Fig. 3: —The light broken lines la- disturbances is apparent, for here belled z, z -j- 1, etc., are contour lines there must be a wavelike pattern in of an isentropic surface. H indicates the contour lines roughly parallel to regions where the isentropic surface the frontal waves in the synoptic sur- is high, and L regions where it is low. face chart. Fig. 3a represents the normal topo- Sharp warm fronts show up in the graphy, while Fig. 3b shows a type contour-line pattern in much the same of topography which is associated manner as do cold fronts, the gradient with frontogenesis within the warm increasing abruptly at the front while air mass subsequent to the appear- the lines remain fairly parallel to the ance of the. trough in the contour front. There are, however, many lines. This latter case is presumably warm fronts on the surface weather associated with frictionally driven maps which are not associated with anticyclonic eddies which we shall this simple contour-line pattern above. treat in more detail later on. Moreover, the surface maps fre- Finally, we may .use the upper-air quently indicate an homogeneous air wind observations as entered directly mass in the warm sector, while the for the observed heights of the isen- isentropic charts show conclusively tropic surface over aerological sound- that the warm air is far from homo- ing stations as a guide to the configu- geneous aloft, but rather character- ration of contour lines. In cases ized by troughs in the contour lines where the pressure distribution aloft suggestive of fronts. Some time after is largely determined by the distribu- their appearance in the contour-line tion of temperature, the winds blow pattern, these troughs may appear on nearly parallel to the contour lines surface charts as regions of fronto- so that domes or ridges are generally genesis. suggesting that such newly to the left of the current flow. ^ ^ H

7+3

Fig. 3. Relation op Contour Line Pattern to Surface Fronts. ISENTROPIC ANALYSIS 143

4. IsENTROPic Flow Patterns

An inspection of the distribution of The absolute circulation (Ca) is equal moisture along an isentropic surface to the sum of the circulation of the covering a sufficiently large area im- fluid chain relative to the earth (Cr) mediately brings to light the fact that and the absolute circulation obtained there are regions of high and of low by the chain if it momentarily were moisture concentration. If the net- fixed to the earth (Cw), or: work of aerological stations were suf- a = Cr + Coj ficiently dense, it would be possible Positive values of Ca and Cr indicate to draw mechanically a series of lines, circulation with cyclonic sense, nega- each denoting a given mixing ratio. In tive values anticyclonic sense. It can this manner one could locate sources be shown that Cw is given by

of moisture, or regions of injection of 0) — 2 C oj S , moist tongues, and likewise the re- where 2 is the area enclosed by the gions from which dry air is supplied. projection of the fluid chain on the Moreover, these currents could be fol- equatorial plane. Thus, if an origin- lowed in a continuous fashion from ally stationary isentropic fluid chain day to day as they travel along the moves northwards without change of isentropic surfaces. Unfortunately the horizontal area it encloses, its the distribution of aerological stations equatorial projection increases, and is in any part of the world much too since (Cr + 2 co S) shall remain sparse to permit such a mechanical constant, Cr must decrease; hence, delineation of moist and dry currents, the chain will gain an increasing and for this reason it becomes neces- amount of anticyclonic circulation sary to develop models and indirect which adds to the circulation orig- clues by means of which characteris- inally possessed by the chain. Simil- tic "flow patterns" may be drawn arly, a southward moving system which approach the real solution. tends to develop a cyclonic circulation. The topic of the source of our moist Cyclonic circulation normally ex- and dry currents is reserved for a presses itself as a cyclonic curvature later section of this chapter. For the of flow, anticyclonic circulation as an present we shall treat the funda- anticyclonic curvature of flow. Thus mental flow patterns which thus far the polar currents of cold dry air have established themselves in the coming out of the north are generally daily isentropic analysis. Once these cyclonically curved, while the warm, models are recognized on the daily moist flows from a southerly direction isentropic chart, the analysis of the have anticyclonic curvatures. These moisture lines becomes appreciably large-scale flows are the fast-moving simplified. streams and generally dominate the The patterns of the large-scale mo- flow patterns observed on the daily tions in the atmosphere appear to be isentropic charts. The axes of such controlled in large part by the rota- streams may be delineated on the tion of the earth. If we consider a isentropic charts as curved lines along fluid chain of particles located in and which the wind velocities are a max- moving with an isentropic surface, it imum. Once these current axes are follows from Bjerknes' circulation determined, they serve as a frame- theorem that the total absolute circu- work for isentropic flow patterns. lation of this chain remains constant Once an air mass is set in motion, as it moves from latitude to latitude. certain adjustments of the pressure 144 AEB MASS ANALYSIS field within and surrounding the cur- sphere) and a trough to the left of rent must take place more or less as the stream. they do in the case of the wake 2. The action of lateral shearing stream, investigated by Tollmien [11]. stresses operating on a current in Thus if momentum is injected into which the velocity varies (as in Fig. a region where no horizontal pressure 2) produces super-gradient winds gradients previously exist, Rossby [12] along the boundaries, and thereby has shown that there will be a bank- causes air to be flung across the iso- ing of the current so that pressure bars from lower to higher pressure, rises along the right edge of the and this tends to build up higher stream and falls along the left edge. pressure along the right edge of the This effect is due to the action of an stream. initially unbalanced Coriolis force 3. The shear zones on either side which attempts to create a new pres- of fast-moving currents are dynami- sure distribution in order to balance cally unstable (as shown by Pekeris the motion. There is thus a tendency [13] ) and tend to break the current for a mutual adjustment of pressure into eddies having the vorticity of the and velocity distributions. These ad- original current profile. Thus, anti- justments are affected whenever at- cyclonic eddies are formed to the right mospheric flow becomes out of balance of fast-moving streams, cyclonic ed- with its pressure gradient. dies to the left. The results of Rossby's theory which The development of an eddy affects are of immediate practical value in the moisture distribution and creates isentropic analysis are: a distinct pattern of moisture lines

1. Fast-moving streams tend to along an isentropic surface. In fig. suffer a "banking" process so that a 4a, for example, we have a zonal dis- ridge of pressure tends to build up to tribution of moisture in an isentropic the right (in the Northern Hemi- surface in middle latitudes. The isen-

FiG. 4.—Successive Stages, (a), (b), (c), (d), in the Development of AN Anticyclonic Eddy as Revealed ry the Moisture Lines. ISENTROPIC ANALYSIS 145 tropic surface itself is higher to the sions of moisture above the chosen north and tilts southward, so that it isentropic surface at either of the may be 5000 m above sea level in the stations in the cross section, and if a north and only 2000 m high in the moist tongue is assumed to lie be- south. Let us now superimpose upon tween stations, the tongue must be this zonal state a velocity field as in- drawn as a narrow vertical filament dicated by the lower half of fig. 2. of moist air—a highly improbable Then air to the south is accelerated condition, and certainly one that is through lateral shear, air is piled up rarely observed. This test is perhaps to the right of the accelerated stream, more clearly illustrated by imagining and the motion takes on a circulatory an isentropic chart (say for — 310°) pattern indicated by the broken ar- where a moist tongue has been en- row. Since the moisture is carried tered between two stations; in the along by the air and the motion is axis of this moist tongue a mixing adiabatic, successive patterns of mois- ratio of 7 g/kg has been indicated. ture lines indicated in figs. 4b to d Applying the cross section test we see are soon developed. that if the section is of the type Once the moist tongue of an eddy shown in the fig. 5a, the moist tongue is sketched in on an isentropic chart is real, while in fig. 5b it would be it is possible, with the help of the highly improbable, because here the cross sections, to apply tests for the moisture lines are quite arbitrarily existence of the tongue in the specific drawn. area chosen. The basis for this test If the eddies remained stationary lies in the empirical fact that signifi- and developed in a regular fashion,

Z10\ 320° 320°

310°

310°-., 310° I- 3- ^00° 4- 300° 7^gA9 30o: @ V

Fig. 5. Illustrating the Cross Section Test fo?. Moist Tongues, (a) Moist Tongue Probable; (b) Moist Tongue High Improbable and Solution to be Abandoned IN Favor of Another More Logical One. cant moist tongues spread out aloft it would be simple to follow the moist and if a moist tongue is present on and dry tongues around them. Their an isentropic surface between aero- life history, however, varies from logical stations which are not more eddy to eddy, and is closely allied than 400 to 600 kilometers apart, it with the energy of the current or cur- generally shows up in the cross sec- rents originally responsible for their tion as an inversion of mixing ratio development. Once the source of (or at least a minimum in the vertical energy of the mother current dimin- gradient of moisture) at one or both ishes, the convergence necessary to of the stations. If there are no inver- maintain the eddy fails and the circu- 146 AIR MASS ANALYSIS lation weakens, finally dissipating or a direction normal to the isobars. merging into some other circulation. In the southeastern quadrant of the Thus the stability of any particular eddy there is a region of sub-gradient eddy may, to some extent, be deduced winds which thus appears as a region from the distribution of velocity of wind divergence. The converging around its center, as shown by Namias air in the other quadrants (super- [14]. Stable eddies will have well gradient winds) piling up into the developed circulations with wind ve- center of the eddy will naturally fol- locities increasing radially outward low into the divergent region, and the from the center in a nearly symme- eddy will follow a path indicated in trical fashion. Such eddies will tend fig. 6. Applying this rule in the gen- to rotate as solids. Once the mother eral case, we may say that frictionally current weakens, the symmetry of driven anticyclonic eddies tend to move the velocity profile tends to vanish into the region in which the tangential and the eddy gradually dissipates. winds about them are lightest. This di- Also, for this reason the moisture rection is normally in the direction of lines may sometime indicate an eddy the mother current. It should be em- pattern which is the result of some phasized, however, that this rule ap- already decayed circulation. plies chiefly in the developing stages By assuming that the smaller anti- of the eddy and when it is character- cyclonic eddies are frictionally driven, ized by a symmetry in the velocity it is possible to deduce from the dis- distribution. The use of the above tribution of velocity around their cen- rules for determining the movement ters the general direction of migra- and stability of anticyclonic eddies tion. Suppose we have an eddy with on the isentropic chart will do much a velocity distribution as indicated in to assist in the analysis of the flow fig. 6. This eddy obviously derives its patterns and in making forecasts of

Fig. 6. Relation of Direction of Movement of Anticyclonic Eddies to Distribution of Wind Velocity. energy from the westerly and north- the movement of moist and dry westerly current, and it may be as- tongues. sumed that the air motion, being non- To the left of fast-moving streams gradient, has a small component in a zone of cyclonic wind shear exists, ISENTROPIC ANALYSIS 147 which tends to develop cyclonic eddies. cyclonic eddy observed in tropical cur- When cyclonic eddies are sharply de- rents moving northward. Where the fined they are generally associated polar air intrudes into the system with occluding or occluded cyclones. from the north it develops cyclonic The dominating current in such cases vorticity in order to counterbalance is not the warm moist air coming the decreasing cyclonic vorticity of from the south, but rather the cold the earth's rotation. Each current dry air streaming into the eddy cyclo- attempts to impart the vorticity to nically from the north. The struc- its surroundings, and this is accom- ture of the cyclonic flow pattern nor- plished through isentropic shearing mally observed in occluding cyclones stresses. Thus a branch of the moist is shown diagrammatically in fig. 7. flow is diverted from the mother cur-

FiG. 7. Fronts Indicated at the Surface and Schematic Flow Pattern Around an Occluded Cyclone as Shown by the Moisture Lines in an Isentropic Sur- face IN Mid-Air.

The flow pattern is indicated by the rent into the cyclonic flow. Thus at moisture lines, and the arrows repre- some point there is branching of the sent the instantaneous flow of dry moist flow, and this point appears (D) and moist (M) currents relative to be situated in the vicinity of the to the movement of the cyclone. In occlusion point on the surface weather the model it is observed that two map. systems are struggling for suprem- If this branching is due chiefly to acy: an anticyclonic moist current, lateral shearing stresses, we may M, to the right, and a cyclonic dry arrive at some valuable rules by as- current, D, to the left. The moist suming that in the region of branch- current, having come up from the ing real horizontal divergence as well south, tends to acquire anticyclonic as divergence of the stream lines is curvature indicated by the directional occurring (Namias [15]). Thus, if the flow arrow to the upper right. This flow pattern prevails through a fairly part of the pattern may thus be con- deep layer of the atmosphere, the sur- sidered as the normal type of anti- face pressure falls in the region be- 148 AIR MASS ANALYSIS low the branching. This effect is, of face may be roughly estimated by the course, superimposed upon the pres- strength of the interacting currents. sure changes due to density advection. Thus a weak anticyclonic eddy will If the region of divergence is situated generally yield to an invading strong some distance from the center of the cyclonic flow of polar air, and in this, surface cyclone, a secondary cyclone case no secondary will result, while may form near the peak of the warm two strong currents of different vor- sector at the ground. ticity will invariably cause large pres- The effects of the branching upon sure falls and lead to deepening and the pressure distribution at the sur- possibly cyclogenesis.

5. The Displacement of Flow Patterns with Height Thus far we have concerned our- eddy is present below a cyclonic eddy^ selves with flow patterns observed in This case is represented schematically one isentropic surface. Experience in fig. 8, where the solid lines repre- has shown (Simmers [16]) that there sent the flow pattern at some isen- is a relatively small difference in the tropic surface, while the broken lines, flow pattern from one isentropic sheet show the flow pattern along an isen- to another. This, however, does not tropic surface ten degrees higher in hold true if we choose an isentropic potential temperature. The domes of surface which is so low that it comes the isentropic surfaces are indicated under the influence of the surface by H and the troughs by L. With friction. The slight displacement of such a vertical distribution of flow- flow pattern with elevation, which oc- patterns it is clear that while the curs above the friction layer, con- lower layers over a region are becom- forms usually with the displacement ing progressively warmer and moister, with elevation of cyclonic and anti- the higher layers are becoming colder cyclonic centers. It should be noted, and drier. The advection thus leads- however, that there are exceptions to two processes in which the poten- and that these are frequently asso- tial energy of the air column is in- ciated with radical changes in creased: (a) where the lower layers weather situation (Namias [17]). are becoming warmer and the upper The most important exception, per- layers are becoming colder, the lapse haps, is the case when an anticyclonic rate is made steeper; (b) since the

1 g/kg 1 3

at 9=300° / --..-' at 9 =310

3 4 5 6 6 5 4 3g/kg

Fig. 8. Flow Patterns at Different Isentropic Surfaces Which Lead* TO Increasing Instability. ISENTROPIC ANALYSIS 149 lower layers are becoming richer in cross sections. Thus in fig. 9A we moisture while the upper layers are have the conservative case where it becoming drier, the energy due to con- makes little difference in the flow pat- vective instability is increasing. This tern whatever isentropic surface is combination of effects makes it easier chosen for analysis, while fig. 9B for frontal activity to produce pre- shows the case in which the flow pat- cipitation, and in general adds to the tern at a surface = 305° would supply of energy available for cyclo- differ appreciably from that on the genesis. It also facilitates the out- surface = 295°. In the latter case break of local showers due to diurnal it is necessary to construct isentropic heating if the moist layer is thick. charts for both these surfaces to ob- A quick test for the conservatism tain a more complete picture of the of any particular isentropic flow pat- atmospheric flow patterns. tern with height is afforded by the

300° 305°

290°

c-290° 3g/kg '5 6 7 7 6 5 4 7 6 5 4 '//////////////////////A

Fig. 9A. a conservative cross-section indi- Fig. 9B.—Cross section indicating that flow cating that choice of isentropic surface will patterns change appreciably from one isen- not materially affect location of major flow tropic surface to another. patterns.

§ 6. The Representation of Gradient Flow in Isentropic Surfaces

The principal reason for the use Montgomery [18]. His development of isentropic charts is that they afford leads to the expression for the stream a means of determining atmospheric function of the gradient wind in an motion independent of assumptions isentropic surface: regarding the existence of gradient ^ = Cp r + $ flow. Nevertheless it is frequently where Cp is the speciflc heat of air desirable to know the gradient flow, at constant pressure, T is the absolute and it appears that the mutual ad- air temperature at the isentropic sur- justment of velocity and pressure face, and $ the geopotential. Using distribution takes place in such a meter-ton-second units <^ is expressed fashion that most of the time cross- in dynamic decimeters, and the value isobar components of the wind are of the constant Cp is approximately small compared with the gradient 1000. flow. If lines for equal values of his

A highly satisfactory method of function ,^ are drawn on an isentropic Tepresenting gradient flow in isen- chart, they form streamlines and tropic surfaces has been suggested by serve a purpose similar to isobars on 150 AIR MASS ANALYSIS a constant level chart.* In regions trajectory of dry and moist tongues where pilot balloon wind data are of the isentropic chart.f There is also lacking these isentropic stream lines considerable advantage in construc- are quite helpful. Moreover, by com- ting the stream function chart before paring the patterns of stream lines completing the isentropic flow pattern. from day to day, and noting the changes of the values, it is possible *Values of y are now being transmitted ij/ daily over the airway and Weather Bureau to get a better idea as to the future teletype circuits in the United States.

§ 7. The Relation of Isentropic Flow to Precipitation Since one of the necessary condi- slope motion may have ceased by the tions for the formation of precipita- time when the synoptic picture was tion is the presence of sufficient mois- obtained. ture content, it is not surprising that Another indication of upslope motion along the isentropic surface is ob- there is generally found some rela- tained from the wind observations. tion between moist tongues and pre- If there are sizeable wind components cipitation areas. In winter, when the normal to the contour lines, and if the stratification is relatively stable over contour patterns are uniquely defined the continents, most of the precipita- by observations from a dense network tion over continental areas is caused of soundings, then it is probable that by frontal action. The isentropic the air is ascending or descending the indicates regions of chart frequently isentropic slope in the direction of ascent or descent of air through the the wind. However, when the con- relative configurations of the moisture tour lines themselves are displaced lines.f A frequent type of flow pat- with the same speed as the wind com- tern is shown in fig. 10, where a ponent normal to them, the wind com- moist tongue ascends the isentropic ponents normal to the contour lines surface. are not indicative of up- or downslope motion. If there is any doubt as to whether there is upslope or downslope motion the observed mixing ratios should be compared with the saturation mixing ratios (or the pressure should be compared with the condensation pressure) in order to find out how much lifting is necessary in order to make the air saturated. In addition, consecutive maps should be compared in order to determine is approaching satu- +g/kg whether the air or not. study of the closed Fig. iO.—Illustrating probable upslope mo- ration A tion of a moist current as deduced from the systems and areas of precipitation relation of moisture lines to contour lines. will give additional information to mentioned that the con- It should be this end. contour figuration of moisture and In regions where the heaviest fron- lines shown in fig. 10 does not always interesting sug- indicate upslope motion, because the tSee in this connection the gestions of Starr to show such changes by- shape of these lines is the result of means of a "relative-motion isentropic chart". (V. Starr, Bidletin Amer. Met. Soc, June„ a lengthy development, and the up- 1940). ISENTROPIC ANALYSIS 151 tal precipitation occurs the gradient dry layer overlying a relatively moist of contour lines is steep and a source stratum of about 2 km thickness. The of moist air is not far removed. The transition zone between the lower precipitation band is normally ori- moist and the overlying dry air is nor- entated to the left of moist tongues so mally a very stable layer, often a that there is probably considerable marked temperature inversion. The upslope motion of the moist air in second type has no discontinuities in this region. temperature and moisture content. In the warmer seasons much of the Furthermore, the air column is not precipitation in continental areas is far from saturation. Type 3 repre- non-frontal in character. This presents a transition between the types cipitation is chiefly of the convective 1 and 2, and here there is a 2-km type, and occurs as local showers and layer of moist air next to the surface, and thundershowers. In Articles VIII with dry air sandwiched in between and IX we discussed the detailed use this stratum and another layer of of energy diagrams for forecasting high moisture content aloft. As in these showers. However, the use of type 1 there is a stable layer between energy diagrams becomes even more the dry and moist air, although less effective when one takes into consi- stable, and as in type 2 the lapse rate deration not only the state rep- aloft is fairly uniform and normally resented by the energy diagram at slightly steeper than the saturated the time of the sounding but also the adiabat, while in type 1 it is almost probable changes with time caused by equal to the dry adiabat. the advection of moist and dry cient to overcome the negative area tongues at various levels. The isen- below and positive areas above for tropic analysis offers by far the most convective impulses from below. Nor- satisfactory method of doing this. mally such impulses (even at the time We shall first discuss a few of the of maximum temperature) are insuffi- characteristic vertical distributions cient to frustrate the negative area of temperature and moisture normally and cause overturning of the whole observed over continental United air column. Type 2 normally gives States in summer. The first type large amounts of available energy for (shown in fig. 11) has an extensive upward impulses that occur at the

2.0 5.0 10 15 10 15 10 15

Fig. 11. Characteristic Vertical Distributions of Temperature and Moisture Observed Over Continental United States in Summer. Numer- als Plotted Along the Ascent Curves Indicate Relative Humidity. (Plot- ted on pseudo-adiabatic charts, j?°-''' vs T, with the dry adiabats (isentropes) of ^ = 290°, 300° A, only.) 152 AIR MASS ANALYSIS time of maximum temperature. This observed over this portion, and we type represents conditional instability may look upon the zonal distribution of a sort which may easily become of velocity as being similar to that realized during the warmer part of pictured in the lower half of fig. 2. the day. Type 3 is very stable for South of such a westerly current an- convective impulses near the surface, ticyclonic eddies forin which create and normally only negative areas will distinct patterns of moisture. This be observed. phenomenon occurs so frequently From the above remarks it might over certain areas of the United be supposed that showers and con- States that mean isentropic charts vective thunderstorms rarely occur constructed for a month, season, with types 1 and 3, while they are or group of the same seasons of common with type 2. While this sim- different years, reveal the eddies ple rule would have considerable suc- through the moisture lines (c/. fig. cess in its application to forecasting, 14, e.g.). The normal flow pattern it would fail in certain cases. Before shows that dry air from the north we discuss these cases, it is possible curls anticyclonically southward while to comment further on such vertical moist air from the south converges distributions of temperature and in a spiral fashion with this dry moisture as are represented in fig. air into the anticyclonic eddy. The 11. In summer the normal tempera- axis of the dry tongue normally runs ture distribution over a large part of through the Mississippi Valley, while the United States is almost baro- the moist tongue generally makes its tropic, and the main concentration of appearance over northern Mexico and solenoids appears to be found along then curves eastward. the northern border of the continent*. See para. 9 infra for a more detailed pic- Consequently, strong westerlies are ture of the normal state.

Fig. 12. Destruction of Dry-Type Stable Zones (shown by arrows) After the Advection of a Moist Tongue Aloft. These soundings were made from June 23rd to 28th, 1937. Numbers to the right of the soundings are the relative and (in parentheses) specific humidities. Clouds are indicated by international symbols. ISENTROPIC ANALYSIS 153

Comparing this pattern with the type 1. Part of the reason for this normal pressure field observed at the is that the stable layer of type 1 surface it will be seen that while the effectively damps out any impulses flow of air in the surface layers over from below, while the same impulses eastern United States is uniformly have a better chance of penetrating from the south and southwest, there the less stable transition zone of type are regions where the current system 3. But if we consider isentropic mix- is reversed aloft. Thus, although the ing and Parr's principle (that this lowest layers of air are generally kind of mixing is more pronounced characterized by considerable homo- the greater the stability), it becomes geneity, there are sections where this clear that in type 1 ascending currents moist and warm air, normally of of moist air from below are quickly Tropical Maritime origin, is overrun robbed of their moisture as they enter by dryer air coming from the north. the stable zone, while in type 3 this ef- Moving southward, the dry air sub- fect is not so pronounced. In the case of sides, so that by the time it reaches type 2 the lateral mixing is less pro- the core of the anticyclonic eddy it nounced than in 1 or 3 and, moreover, has become warmer and drier than the mixing in this case does not de- air anywhere in its vicinity. This plete the moisture of the rising cur- type of air mass (Ts, or S) is discussed rent appreciably. Therefore, the con- in Prof. Willett's chapter on air mass densation levels of type 1 are raised properties and in the appendix thereto to high levels, and latent heat of con- by Mr. Showalter. densation is not made available for Soundings of type 1 may generally the grov^rth of Cu clouds and showers. be explained on the above basis. The Moreover, the increased lateral mix- stable transition zones between the ing with type 1 reduces the total up- moist and overlying dry air are main- ward momentum of impulses. Cumu- tained in part by continued subsi- lus grov^rth is, however, more likely in dence. These stable zones exist for type 3 and most likely in type 2. The long stretches of time during the sum- few thunderstorms observed in con- mer season, and, when they are es- nection with soundings of type 1 are pecially tenacious, periods of drought likely to be high-level thundershowers, result. They are frequently destroyed, and the precipitation from them however, after the advection of a rarely reaches the ground in appre- moist air current aloft. Fig. 12 shows ciable amounts, since it is evaporated some typical examples when dry sta- into dry air below the cloud base. ble layers (marked by arrows) were In connection with type 3 it has destroyed through advection of moist been pointed out that frequently the air aloft. Experience shows that lapse rate is so stable in the lower soundings of type 1 will be trans- layers, even at the time of maximum formed into type 3 through advection temperature, that upward impulses of moist tongues aloft. Through are soon damped out. Convective turbulent redistribution of heat and thundershowers which occur with moisture, and through radiative ex- such stratifications normally occur at change of heat, soundings of type 3 night-time, especially in the early may be transformed into type 2. morning hours. The thunderstorms Summer showers and thunder- observed over midwestern United showers occur frequently with type 3, States in summer appear to be mostly while they are rarely observed with of this type, for the diurnal fre- 154 AIR MASS ANALYSIS quency distribution of thunderstorms The problem of forecasting summer here shows a night-time maximum at showers therefore depends not only this season. The more probable con- upon the stratification existing aloft clusion is that the impulses generating in the early morning when soundings these storms originate not in the are made, nor entirely upon the lower layers where the stability is so changes brought about by diurnal marked, but in the upper layers. One heating (see Arts. II, VIII), but also factor which readily suggests itself upon the advection of moist and dry as an important one is radiational tongues aloft. The best method of cooling of the moist air aloft. At estimating these advective changes the top of these moist currents is nor- lies in the isentropic analysis. In this mally found another stable zone, fre- manner we are able to detect in ad- quently an inversion. Cooling of vance the likelihood of soundings of moist air aloft becomes intensified any of the above types being trans- when clouds form at the boundary formed into other types through surface, for clouds act as black bodies. advection. The process thus envisioned demands When reliable isentropic charts are that convective stirring occurs in the at hand, together with the corres- layer cooled from above, just as it ponding cross sections, it is possible must occur in a layer heated from be- to obtain information of forecasting low. However, the processes of re- value which is not easily obtained moving heat aloft and supplying it from other charts. The problem of from below probably lead to convec- shower and thunderstorm forecasting, tion of a somewhat different nature. therefore, revolves chiefly about the Heating from below, when associated determination of the lapse rate and with steep lapse rates, may result in the source and availability of mois- rapid upward motions of small ele- ture. Tongues of dry and moist air, ments, while cooling from above is as shown by the isentropic charts, probably slower acting and is trans- may be identified from day to day by ferred slowly downward. means of these charts. In summer it For a thunderstorm to become en- is found almost invariably that thun- ergetic and produce sizable amounts derstorm activity and showers are of precipitation it must have available associated with the moist tongues, an ample supply of moisture. Since while the dry tongues are free of in summer the maximum concentra- convective precipitation. Furthermore, tion of moisture is generally in the by making use of cross sections one surface layers, it follows that what- is able to form an idea of the repre- ever the origin of the convection, over- sentativeness of the chosen isentropic turning must eventually take place chart. Sources of moisture indicated throughout these lowest layers if the within the frictional layer may be storm is to become of appreciable found to be shallow and not represen- intensity. Thus if convection aloft is tative of conditions in higher isen- caused, let us say, by radiational cool- tropic surfaces. The presence or in- ing of a cloud layer, we must draw vasion of dry air aloft would then upon some supply of energy to carry counteract the possibility of showers this convection into the moisture-rich and thunderstorms. Thus, though an surface layers. This energy some- energy diagram may offer indications times appears in layers which are of possibilities for shower activity, conditionally unstable and moist. one should use the isentropic chart to —

ISENTROPIC ANALYSIS 155 take into account any likely changes. tions and velocities on the isentropic Suppose, for example, that an energy chart provide the chief indices of the diagram indicates large positive areas magnitude of both these factors. For and that moist air extends to high example, lateral mixing is most fa- levels—both indications of thunder- vored in regions where the horizontal storm activity during the day. If a wind shear is greatest. After con- tongue of dry air is displacing the sidering modifying factors, it is neces- moist air at upper levels, the prob- sary to determine the layer from ability of thunderstorms is greatly which the principal radiational loss lessened. Then again, the horizontal of energy will take place. This layer extent of the source of moisture must is not difficult to place; it is usually be considered. A narrow jet of moist the most pronounced dry inversion of air will suffer lateral mixing with the sounding. If it appears at low the dry air flanking it on both sides, levels, in general below about 2 km, and this dessicating process will act it will be of little significance in help- against thunderstorm formation. The ing large-scale convective activity, as showers, if they occur at all, will then was explained in the discussion of be restricted to the very central por- the lateral mixing in the dry-inver- tion of the moist tongue (along its sion. But the radiational emission horizontal axis), where the moisture layer, when at higher levels, becomes is least affected by the admixture of increasingly important, for the heat dry air. On the other hand, extensive lost to space at the boundary helps set regions or broad tongues of moisture off convection through a thick layer may remain comparatively unaltered of atmosphere. The rate of cooling by lateral mixing, and thereby pro- at cloud tops is appreciably greater vide ideal conditions for continued than from unsaturated air under the thunderstorm activity. same conditions, and therefore the Thunderstorms caused, at least in nearness to saturation of the moist part, by radiation from upper levels layer must be considered. are best forecast by the use of energy If the lower layers of the atmos- diagrams in conjunction with the phere are too cold, the tephigram will isentropic chart. The first step is to indicate that convective energy aloft decide what changes in the tempera- will be dissipated before it can re- ture and moisture distribution are ceive supplies of moisture from the likely to take place. The changes in lower layers. In this case, even though the flow pattern of moisture are the chief emission layer is at high brought about mainly through advec- levels, thunderstorms are not likely tion and lateral mixing. Wind direc- to occur.

§ 8. The Processes which Tend TO Disrupt the Continuity of Isentropic Analysis From the standpoint of following particles from day to day. By fol- the same sheet of air from day to day lowing these identical sheets and the ideal method of representation describing the motion of elements would be one in which non-adiabatic with respect to such sheets, one would as well as adiabatic influences were be using the Lagrangian method of taken into consideration. With such * Other writers have used the expression a method one could construct charts "equi-substantial sheet" instead of "substantial", when referring to a fluid sheet rather along substantial sheets* that is, — than to a surface of a solid ; but it does not to this fine and cumber- sheets which contain the same air seem necessary make some distinction. Ed. 156 AIR MASS ANALYSIS describing the changes in the at- substantial surfaces and also tend mosphere. While at present it is not to transport moisture across the possible to chart exactly substantial isentropic surfaces. These non-adi- surfaces, there is much evidence to abatic processes are mainly due to: indicate that isentropic surfaces do (a) radiation, (b) evaporation and not depart appreciably from substan- condensation, and (c) convection. tial surfaces. Thus, the isentropic While the influences of these pro- method of analysis is essentially a cesses may be appreciable over Lagrangian method. In a study of lengthy intervals of time, they are subsidence Namias [20] has shown usually insufficient for disrupting the that the potential temperatures at the fundamental isentropic flow patterns bases and at the tops of subsidence in- from one day to the next. versions remain fairly constant from The influence of radiative cooling is day to day. Thus, if, in such cases, illustrated in fig. 13. As cooling isentropic surfaces are used, it is proceeds, the temperature distribution reasonably certain that we are deal- changes from A to B to C. The sub- ing with the same sheet of air parti- stantial surfaces do not change eleva- cles from day to day. Moreover, it tion but since the temperature de- is frequently observed that sand- creases, the height of any given isen- wiched layers of dry and moist air tropic surface increases from day to remain within the same isentropic day. Since the normal moisture dis- sheets for several days. From these tribution is one in which mixing ratio observations it appears that, as a decreases with elevation, the mixing first approximation, we may consider ratio observed in a given isentropic isentropic surfaces as substantial sur- surface decreases with time. Since faces. the rate of radiational cooling in the Nevertheless, there are always at free atmosphere is usually small com- work non-adiabatic processes which pared with the adiabatic cooling, it tend to destroy the conservatism of does not destroy the essential char- isentropic surfaces and to raise or acter of the flow pattern. This slow lower the isentropes relative to the rate of free-air cooling is indicated

5.0 10 15 by the cooling curves computed by Moller [21], which suggest that the mean temperature change resulting from the radiative unbalance in the atmosphere hardly exceeds 1.5C° per day,* which with normal lapse rate corresponds to a vertical displacement

*Elsasser (Unpublished MS) has recomputed such cooling curves on the basis of newer data on the water vapor absorption spectrum. In general his values do not differ excessively from Moller's. However, both Holler's and Elsasser's curves are based on monthly means of upper-air conditions. On individual days the cooling must be much greater sometimes, perhaps as much as 10° or 15° C per day from a saturated warm stratum with a deep dry inversion above it. The figure 1.5° C quoted

is for mid-latitudes ; Elsasser's (Bvll. Amer. Met. Soc, May 1940) mean values for Florida soundings even in winter show over 2.0° C per day cooling at moderate elevations. Elsasser Fig. 13.—Illustrating the influence of non- has published a radiation chai-t with which adiabatic cooling on the elevation of an isen- radiation in individual soundings can be com- tropic surface. puted (Calif. Inst. Techn. 1939).—iJ. G. Stone. ISENTROPIC ANALYSIS 157

of the isentropic surface of about in tropical air. In this case isen- 300 m in one day. Nevertheless, it is tropic surfaces remain practically sub- at times necessary to introduce this stantial surfaces. factor to explain changes in moisture If condensation and precipitation content or height of the isentropic set in within the chosen isentropic surface which cannot satisfactorily be sheet, latent heat is liberated and the explained by advection or other causes. potential temperature of the substan- Where the isentropic surface is not tial surface is raised. The isentropic far from snow-covered mountains, surface is then found at lower levels, cooling by radiation and eddy trans- and, since the specific humidity nor- fer of heat must frequently be con- mally increases downward, the specific sidered. humidity in the isentropic surface in- Opposite effects are observed when creases. This increase might errone- there is non-adiabatic heating. Then ously be interpreted as being due to a substantial surface has its poten- advection from a neighboring source tial temperature raised so that the of moisture. isentropic surface is lowered, and When precipitation falls through since the specific humidity normally an isentropic sheet which is not sat- decreases with elevation, there ap- urated with moisture, evaporation pears to be an increase in moisture will cool the air while the specific within the affected area of the isen- humidity increases. This lowers the tropic chart. This type of non-adi- potential temperature of the substan- abatic modification is significant tial surface, and raises the isentropic when the isentropic surface is near surface. If the moisture content de- the ground. The influence is greatest creases with elevation the mixing in continental areas during the sum- ratio at the chosen isentropic surface mer season. It is also important in decreases in proportion to the humid- mountainous country during all sea- ity gradient. On the other hand, if sons. the moisture content increases with

Let us consider next the non-adiab- elevation (as it often does along well atic effects produced by evaporation defined frontal surfaces) the mixing and condensation. Since condensation ratio will increase. The increase in liberates and evaporation consumes moisture with elevation is usually so heat, it becomes important to know slight that, though the isentropic sur- whether these processes occur above, face rises, little change in the pattern within or below the isentropic sheet of moisture results. under discussion. Probably the most significant proc- If the chosen isentropic surface lies ess at work in causing isentropic sur- above the region where condensation faces to depart from substantial sur- occurs, its characteristics will not be faces is convection, because vertical materially affected. An example is currents are highly effective in trans- afforded by the instability snow show- porting moisture to higher levels. If ers of polar continental air masses of it were not for the replenishment of winter. These flurries are generally moisture by convective currents, the formed in a shallow layer of air next moist tongues which are not associated to the earth's surface—a layer which with upslide motion along frontal sur- is far below the representative isen- faces would soon be dissipated through tropic surfaces which are chosen so lateral mixing with the dry air flank- as not to intersect the ground even ing them. 158 AIR MASS ANALYSIS

In the discussion of the influence of spread convection. The convective convection on the moisture patterns on transfer of moisture may then at the the isentropic chart it is convenient to beginning of this process radically distinguish between widespread con- change the moisture pattern aloft. vection within unstable air masses This is particularly the case in Polar and convection associated with fronts. continental air when it moves over an Convection that occurs along fronts ocean, because the convective currents (notably cold fronts) is usually re- will then transport much moisture to stricted to a narrow zone which co- high levels. The convection that oc- incides with a moist tongue on the curs in unstable Polar continental air isentropic chart. While the vertical moving over land in winter does not currents transport moisture to higher usually reach up to the representative levels, water is also precipitated from isentropic surface; it therefore does the frontal cloud system. The convec- not appreciably influence the moisture tion which occurs along such fronts pattern aloft. merely replenishes the moisture con- From the above it follows that the tent of the moist tongue, and it does occurrence of convective as well as not disrupt the continuity of the isen- frontal precipitation is closely related tropic analysis. The same also applies to the moist tongues, and that the to purely local convection ("pinpoint isentropic charts afford the best convection"). The matter may, how- means for analyzing the processes in ever, be different in cases of wide- the free atmosphere.

NORMAL SUMMER IS&HTROPIC C-HART-^ " 315° A \_

Fig. 14. The Normal Flow Pattern Over United States in Summer. This chart is based upon aerological data for summer months from July, 1934, through August, 1939. It was constructed by averaging values interpolated at 5 degree intersections of longitude and latitude from analyzed monthly mean isentropic charts. The winds are normal resultant upper-air winds. ISENTROPIC ANALYSIS 159

9. The Mean State of the Atmosphere as Revealed by Isentropic Charts

If the daily aerological soundings the United States is south of this during a given month are averaged front and is within what appears as for various stations, we may construct a thermally homogeneous air mass. isentropic charts and cross sections In spite of the zonal homogeneity of representing the mean state of the temperature, and the consequent lack atmosphere for that month. The mean of solenoids to generate kinetic en- air flow may be obtained by com- ergy, there is observed a prevailing puting the resultant winds from pilot- eastward flow of the tropical air. Ac- balloon observations. (See the mean cording to Rossby [22] the eastward charts published monthly in the Mo. current in the homogeneous air is Wea Rev.). Similarly, it is possible maintained by frictional stresses from to construct mean seasonal isen- the much stronger westerly current tropic charts, and, if data were avail- to the north, and this energy is con- able, normal charts. An example is tinually being dissipated in the form shown in fig. 14. of eddies further to the south. If The outstanding feature of the such eddies are maintained in more normal summer pattern is the ex- or less fixed locations over a suffi- istence of two well-defined anticyclonic ciently long period of time, the mean cells — one centered over western chart will display an eddy pattern in Texas, the other somewhere off the the moisture lines and in upper-air southeastern coastal states. Some winds. The mean isentropic charts light on the question of the formation for individual summer months invar- of these eddies is furnished by north- iably reveal such eddies, and most of south atmospheric cross sections, a the time there are observed two anti- typical one for the summer season be- cyclonic cells placed about as they are ing reproduced in fig. 15. This see- in fig. 14.

SAULT STE MARIE DETROIT DAVTON NASHVILLE MONTGOMERY PENSACOLA

Fig. 15.—North-south vertical cross section for August, 1936, showing the distribution of potential temperature (broken lines) and specific humidity (full lines). tion brings out the well-known fact In all the mean summer isentropic that over North America the prin- charts studied there has been a moist cipal summertime Polar front is gen- tongue projecting from northern Mex- erally found in the vicinity of the ico recurving towards the northeast Canadian border. Most of the time and east. The region covered by this 160 AIR MASS ANALYSIS tongue has a maximum of precipita- Namias [24]). Thus during the tion in summer. It has been sug- month of August, 1936, when one of gested by Wexler [23] that this pre- the most severe droughts and heat ferred site for the anticyclonic eddy waves occurred in the mid-west, the is largely due to topography and re- mean monthly pattern showed only sults from the field of solenoids to the one very extensive anticyclonic eddy north as well as from the field of sole- covering the entire country rather noids established between the warm than the normal double cellular pat- Rocky Mountain region and the colder tern. Pacific region. In winter, when the mid-latitude The point of injection of the moist solenoid field is situated farther to tongue of the eastern eddy is nor- the south, the mean isentropic charts mally over Florida, in which region do not generally display any outstand- there is a summer maximum of rain- ing eddies. Simultaneously, the daily fall and a high frequency of thunder- charts sho"w pronounced eddies with storms. moist and dry tongues. The in- While there is a similarity of mean dividual eddies then move rapidly, monthly isentropic charts for different without preferring any particular summer months and from year to site. While the above refers to the year, it should not be inferred that conditions over the North American the moisture patterns are always the continent, there can be little doubt same. Considerable deviations from that the principles outlined here ap- the mean state are always associated ply in a general way throughout the with considerable anomalies in rain- world. fall and temperature (Wexler and

§ 10. References

II] Rossby, C.-G., Thermodynamics Applied [ 9 ] Grimminger,, G., The Intensity of Lat- to Air Mass Analysis. Massachusetts eral Mixing in the Atmosphere as Deter- Institute of Technology Meteorological mined from Isentropic Charts. Transac- Pavers, Vol. I, No. 3, 1932. tions of the American Geophysical Union, Nineteenth Annual Meeting, 1938, Pt. I, [ 2 ] Rossby, C.-G., and Collaborators, Aero- 163. logical Evidence of Large-Scale Mixing p. in the Atmospheie. Transactions of the American Geophysical Union. 18th An- [10] Byers, H. R., On the Thermodynamic Interpretation of Isentropdq (Charts. nual Meeting, Pt. I, pp. 130-136, 1937. Monthly Weather Review, Vol. 66, No. 3, 13] Rossby, C.-G.. and Collaborators, Isen- 1938. tropic Analysis. Bulletin of the Ameri- can Metecrolociical Society, June-July, [11] Tollmien, W., Berechnung turbulenter Vol. 18, pp. 201-209, 1937. Ausbreitungsvorgange, Zeitschrift fiir Angewandte Mathematik and Mechanik, t 4 ] Shaw, Sir Napier : Manual of Meteor- Vol. 6, p. 468, 1926. ology. Vol. 3, The Physical Processes of Weather. Cambridge University Press, [12] Rossby, C.-G., On the Mutual Adjust- 1933, pp. 259-266. ment of Pressure and Velocity Distribu-

[ 5 ] Rossby, C.-G., Dynamics of Steady Ocean tions in Certain Simple Current Systems, Currents in the Light of Experimental I and II. Sears Frundation : Journal of Fluid Mechanics. Papers in Physical Marine Res^a^-ch, Vol. I, Nos. 1 and 3, Oceanography and Meteorology, Massa- 1937 and 1938. chusetts Institute of Tte^f-hnology and Woods Hole Oceanographic Institution, [13] Pekeris, C. L., Wave-Distribution in a Homogeneous Curi-ent. Transactions of Vol. V, No. 1, 1936. the American Geophysical Union, Nine- 6 I ] Parr, A. E., On the Probable Relation- teenth Annual Meeting, 1938, Pt. I, pp. ship Between the Vertical Stability and 163-164. Lateral Mixing Processes. Journal du Conseil, Vol. XI, No. 3, 1936. [14] Namias. J., Forecasting Significance of Anticyclonic Eddies on Isentropic Sur- t 7 ] Ekman, V. W., Studien zur Dynamik der Meeresstromungen, Gerlands Beitr. Geo- faces. Transactions of the American Geophysical Union, Nineteenth Annual physik. Vol. 36. p. 385, 1932. Meeting, 1938, Pt. I, pp. 174-176. 18] Rossby, C.-G., Note on Shearing Stresses Caused by Large-Scale Lateral Mixing, [15] Namias, J., The Use of Isentropic Analy- Proceedings of the Fifth International sis in Short Term Forecasting. Journal Congress of Applied Mechanics, 193S. N. of the Aeronautical Sciences, Vol. 6, No. Y., 1939, pp. 379-381. 7, 1939. ISENTROPIC ANALYSIS 161

[16] Simmers, R. G., Isentropic Analysis of a of Dry-type Moisture Discontinuities not Case of Anticyclogenesis. Part I C of Developed by Subsidence, Monthly Weather Fluid Mechanics Applied to the Study of Review, Vol. 64, No. 11, 1936. Atmospheric Circulations, Papers in [21] Mciller, F., Die Warmequellen in der Physical Oceanography and Meteorology, freien Atmosphare, Meteorologische Zeit- Massachusetts Institute of Technology schrift. Vol. 52, p. 408, 1935. and Woods Hole Oceanographic Institu- [22] Rossby, C.-G., the Maintenance of tion, Vol. VII, No. 1, 1938. On the Westerlies South of the Polar Front, [17] Namias, J., Two Important Factors Con- Part lA of Fluid Mechanics Applied to trolling Winter-time Precipitation in the the Study of Atmospheric Circulations, Southeastern United States. Transactions Papers in Physical Oceanography and of the American Geophysical Union, Meteorology, Massachusetts Institute of 1939, Pt. Ill, pp. 341-347. Technology and Woods Hole Oceano- [18] Montgomery, R. B., A Suggested Method graphic Institution, Vol. VII, No. 1, for Representing Gradient Flow in Isen- 1938. tropic Surfaces, Bulletin of the American [23] Wexler, H., Observed Transverse Circula- Meteorological Society, Vol. 18, No. 6-7, tions in the Atmosphere and their Climat- June-July, 1937. ological Implications. Thesis for Doctor's [19] Namias, J., Thunderstorm Forecasting degree at Massachusetts Institute of with the Aid of Isentropic Charts. Bulle- Technology, (as yet unpublished), 1939. tin of the American Meteorological Soci- [24] Wexler, H. and Namias, J., Mean ety, Vol. 19, No. 1, Jan. 1938. Monthly Isentropic Charts and their Re- [20] Namias, J., Subsidence within the At- lation to Departures of Summer Rainfall. mosphere, Harvard Meteorological Stud- Transactions of the American Geophysical ies, No. 2, 1934. Union, Nineteenth Annual Meeting, 1938, Namias, J., Structure and Maintenance Pt. I, pp. 164-170.

Isentropic Analysis of a Thunderstorm Situation, June 22-27, 1937 The following' series of charts was Namias' chapter on Isentropic Analy- used by Mr. Namias to illustrate his sis) so that showers could occur. epoch-making paper on thunderstorm The advection of this moist air at forecasting with the aid of isentropic intermediate levels destroys the pre- analysis {Bull. Amer. Met. Soc, Jan. existing dry-type inversions (see Fig.

1938). 9, below) and results in less stable The tephigram in Figure 1 failed to lapse rates in these layers. Conse- give evidence of liability to showers quently parcels of air rising from the since there was a large negative area, surface into this region will (by but this was in the warm sector (Fig. Parr's principle) undergo less lateral 3) and thunderstorms actually oc- (isentropic) mixing with the environ- curred in the vicinity that afternoon. ment. Moreover, since the convection Figure 2 gave every indication for now takes place in a generally moist showers but none occurred anywhere stratum, the condensation levels of near the station that day. Therefore rising surface particles are low enough the assumption that any one particle for upward pulses to reach, thus mak- or mass of air rises adiabatically ing available for convection the heat through a resting medium and that of condensation. In this way the ad- airplane soundings taken in the early vance of a moist tongue aloft may be morning are representative of upper accompanied by a train of showers; air conditions for the rest of the day this interpretation is given in Fig. 8 are clearly invalid in some cases such for the period under discussion. The as these. A study of these cases with forecasted showers at San Antonio on the isentropic charts and cross-sections the 27th failed to occur (Cf. Fig. 12, shown in Figures 4-7 permits these ex- Article X) because the center ceptions to be foreseen. The isentropic Namias' charts (Figs. 4 and 6) show a large of the moist tongue passed somewhat moist tongue advancing over Detroit to the north and the Gulf influence kept on the 23rd-24th which rapidly in- the lower levels too cool and stable creases the specific humidity by many (showers did occur farther west, how- grams (see Fig. 9, also Fig. 12 of Mr. ever).—i2. G. S. 162 AIR MASS ANALYSIS

Fig. 1. Tephigram of the Airplane Sounding at Detroit, Michigan, June 24, 1937, Begun at 4:00 a.m., E. S. T. (Specific humidities entered beside the solid line of the sounding. The dotted line is the path of a particle rising from the surface after it attained the maximum temperature of that day. The broken line AB is a pseudo-adiabat, the significance of which is explained in the text. Areas horizontally shaded represent positive energy while those shaded vertically indicate negative energy, which opposes convection.)

35 ^30 nlP TEMPERATURE "C

Fig. 2. Tephigram of the Airplane Sounding at San Antonio, Texas, June 27, 1937, 2.00 a.m. E. S. T. (For explanation see legend to Fig. 1.) ISENTROPIC ANALYSIS 163

9A 95 9.6*«i^^ a7 98 9^ Oo"

HIGH ''PC

^1 N,

Fig. 3. Synoptic Chart of Sukpack Weather Over United States at 7:30 a.m., E. S. T., June 24, 1937. (Cold fronts are indicated by heavy solid lines, warm fronts by dotted lines, and occluded fronts by alternately dashed and dotted lines. The hatching indicates areas where precipitation is falling at the time of observation. Air-mass symbols are those customarily in use in the United States and introduced at the Massachu- setts Institute of Technology. Surface observations at or near aerological stations [circles] are entered in the custom^ary manner. To the right of the circles from top to bottom: temperature and dew point (°F), pressure, and precipitation. Winds are indicated by arrows, the numbers of half- barbs corresponding to Beaufort numbers of force. To the left of the station are the clouds in international symbols, and the pressure characteristic and change in the preceding three hours.) 164 AIR MASS ANALYSIS

e = 310° JUNE 23, 1937 AM

Fig. 4. Isentropic Chart Constructed from Aerological Observations Made in the Early Morning op June 23, 1937. (The explanation of the construction and the legends is given after Fig. 7.)

SAULT STE MARIE DETROIT DAYTON NASHVILLE MONTGOMERY PENSACOLA -

Fig. 5. Vertical Cross-Section Through the Atmosphere from St. Ste Marie, Michigan, to Pensacola, Florida, on June 23, 1937, Early a.m. (The explanation of the symbols is given after Fig. 7.) ISENTROPIC ANALYSIS 165

= 310° JUNE 24, 1937 A.M

Fig. 6. ISENTROPic Chart Constructed from Aerological Observations of THE Early Morning of June 24, 1937. (For explanation of construction and symbols after Fig. 7.)

SAULT STE MARIE DETROT DAYTON NASHVILLE MONTGOMERY PENSACOLA

Fig. 7. Vertical Cross-Section Through the Atmosphere from St. Ste. Marie, Michigan, to Pensacola, Florida, on June 24, 1937. (The explanation of symbols is given below.) 166 AIR MASS ANALYSIS

Explanatory Legends For Figures 4, 5, 6 and 7

Figures 4 and 6 are charts constructed upon a surface of constant entropy

(constant potential-temperature) . For these cases the particular value of potential temperature chosen was 310°. Solid lines are lines of specific humidity while dotted lines are lines of elevation (in meters) of the chosen surface above sea level. "M" signifies the center of a moist tongue, "D" the center of a dry tongue. "H" and "L" are entered at the crests and troughs of the isentropic sheet. The numbers to the right of the aerological stations are, in the order listed, the specific humidity, the elevation, and the relative humidity at the given isentropic sheet. To the left of the station is entered the pressure, in millibars, of the layer bounded by the 305° and 310° surfaces of potential temperature. The change from day to day in these values offers indications of convergence and divergence. Winds at the isentropic surface are shown by arrows, the number of half-barbs being roughly equivalent to Beaufort numbers of the scale of wind force. Clouds are indicated by the international cloud symbols. Subscripts give the amount of cloud and arrows the direction of movement. If the letter "b" appears following the symbol the clouds are below the isentropic sheet, if elevations are given the clouds penetrate the sheet, and if nothing is appended they are above it. An asterisk (*) indicates that the clouds are within the range of the sounding, yet no height was recorded. Heavy arrows represent the probable path of the tongues with respect to the isentropic surface (that is, choosing a coordinate system fixed to the isentropic surface).

Figures 5 and 7 are vertical cross-sections extending north-south from Sault Ste. Marie, Michigan, to Pensacola, Florida. The evenly spaced horizontal lines represent full kilometers of height. Solid lines are drawn for specific humidity, dashed lines for potential temperature. The humidities in the individual soundings are entered to the left and the potential temperatures to the right of the vertical. Winds are drawn so that north is to the left of the cross-section. For example, at 3 km over Dayton on the 23rd (fig. 5) there is a N wind of force six. Clouds are indicated, as in figures 4 and 6, by the international system; those above the soundings are either above the top of the ascent, or, if accompanied by an asterisk, within the levels penetrated by the sounding but not placed specifically. Here again "M" stands for moist, "D" for dry. ISENTROPIC ANALYSIS 167

Fig. 8. Trajectory of the Center of Maximum Thunderstorm Activity Following the Invasion of a Tongue op Moist Air Aloft; and Posi- tions OF Airplane Sounding Stations Used in This Analysis (circles). (The black squares mark the successive positions of the center of thunderstorm activity for the twelve-hour periods preceding the dates entered beside them; these w^ere fixed vsrith the aid of thunderstorm reports and 12-hourly amounts of precipitation.)

TEMPERATURE -t Fig. 9. Lapse-Rate Diagrams of Soundings Discussed in this Report. (The scales are such that a 45° line sloping upwards from right to left would represent the dry adiabat. Numbers to the right of these soundings are the relative and (in parentheses) specific humidities. Clouds are indicated by the International symbols of 1932. Arrows mark off dry-type moisture discontinuities.) 168 AIR MASS ANALYSIS

Analysis of the Rainfall Situation over the Western States May 6-7, 1938, by Means of Air Mass and Isentropic Charts

The surface maps and isentropic to convergence ahead of the cold front chart below are from the article by- over Texas; the rain over the Missouri Mr. R. H. Weightman in the Bull. and Mississippi valleys is definitely Amer. Met. Soc, April 1939, and were frontal; the northern Rocky Mountain analyzed at the U. S. Weather Bureau, rain area is due to instability in a Washington. The isentropic chart il- moist tongue ascending from the south lustrates the use of condensation pres- (in the northwest the 303 "-surface sures practiced by the Bureau. The was above the tops of the soundings relation of the surface fronts and of on May 7) ; the Colorado-New Mexico the isentropic flow and moisture dis- rain belt is related both to the surface tribution to the rainfall patterns can fronts and to the ascent of the moist be readily interpreted in light of the tongue. The eastward advance of the principles outlined by Mr. Namias. moist tongue brings rain over Iowa on The rain along the Gulf coast is ac- the a.m. of the 7th.—i2. G. S. credited to prefrontal instability due

gQ g9ov~-^^oi^ 9^:9M£'\^[JW

Isobars, o - ^.Surface Occluded Fronr, Surface Cofd Fronf: '^ Upper Occluded Front Upper Cold Front { Warm Frpntogenesis. Surface l^arm Fronl * Cold Frontg^*nesls.

Upper: Warm Fronl^ 1 Stationary Fronh^:^^ .

Fig. 1. Surface Map for 7.30 A.M. (E. S. T.) May 6, 1938 (shaded area rain falling at time of observation). ISENTROPIC ANALYSIS 169

MAY 7, 1938 Potential Tf'mperafurf ^jsoo/ono ^-J^ '-y\ao

=.., o, .;„ Shaded Greet ^hows Where "^^^'^^ Pressure Equals Condensafton Pressure.

Fig. 2. Isentropic Chart for 5.30 A.M., May 7, 1938

12 ft HOURS ENDING 7 30 M , MAY 6, 1938 12 HOURS ENDING 7 30AM .MAY 7. 1938

RAINFALL PATTERNS

(2 HOURS ENDING 7 30 P M , MAY G . 1938 170 AIR MASS ANALYSIS

Fig. 4. Surface Map for 7.30 P.M. (E. S. T.) May 6, 1938. ISENTROPIC ANALYSIS 171

Fig. 5. Surface IVTap for 7.30 A.M. (E. S. T.) May 7, 1938 172 AIR MASS ANALYSIS

Examples of Upper-Air Cross-Sections Showing Interpretations of the Tropopause, etc.

Fig. 1. Vertical cross-section from Madrid to Moscow, A.M. of Feb. 17, 1935. Isotherms in °C, fronts and tropopauses heavy black lines; dashed lines for subsidence inversions (troposphere) and for indefinite tropopauses (being- formed or dissolved). The overlapping of the multiple tropopauses is called for by the theory of Palmen, that the adiabatic cooling or heating from the pumping effect of passing disturbances and highs in the troposphere causes the tropopause to be destroyed at one level and reform at higher or lower levels as the case may be. Only a few soundings (vertical ordinates) were available for this analysis by Bjerknes and Palmen (Geofys. Piibl., v. 12, no. 2, 1937, p. 52) but experience from other cases analyzed permits the interpo- lations. The fronts are drawn double-lined, indica,ting top and bottom of the frontal zone of inversion or relative stability which is typical of soundings through fronts. The sti-atosphere is low and warm over the surface cold-air dome ("high") but high and cold over the surface low pressure. Note that the warm front connects vrith the tropopause in this case, but the cold air is shallo'w. The surface weather chart and streamlines of the tropical air flow in the warm sector above the friction layer and at the slopes of the fronts is shown in Fig. 2. Fig. 3 shows the tropopause and frontal at the same synoptic hour.

Fig. 2. Fronts and warm-air streamlines, Feb. 17, 1935, 07h. The tropical air has been far to the north over the Atlantic and is returning into the cyclone as a NW wind descending over the cold front. CHARACTERISTIC AIR MASS PROPERTIES 173

' IRQPOPAUSE fUlULllL '

17'4 AIR MASS ANALYSIS

CD C3 O 0) S^ g CD CS ^-P o^.a.^2^.

X 3

bjoJii+^ w

s^M^ j^^ g ^.^.^ ^ u^ S

uj ;-; CS — CS' 1-1 _, C3 ?-i

:^^,o cu 1>-+^ M bjo o -^ —' 9 -^f as o •::3 c as cS (D

'"-" _T3 &JO-S^. 3'^-:::;

O m 0) • p< ''•sxlsl^---^-^s.s- ^-^1 ',i«i CS OS

TO Pi,—I -l-i Cl.'^

CT3 o =* S S a; S > I o3t5 S-S^ * aJ+itfH^coPHaSP* UJ w uj _ . ,0 ^ w qj^co f-i7^ 01 ft" o ,^-^^ i^ T3 (-I'M f= R £; iH i^ M 2

'^' (-^ F-iF-i -4-* ^y 2-1 *—

• -^ P-S o

5n c a) i pi 4^ > Co) .a) r5 iW ni >^ oS ^ M i::

c3 ^ ^ w O cc tS

Bergeron's model (see p. 122) incorporates most of the features shown in these examples. There are, however, many occasions when both cold and warm fronts of a system apparently reach to the tropopause, though presumably this occurs less commonly in the lower middle latitudes (southern United States) than farther north (Europe) where the tropopause is normally lower. The Tarity of fronts above 5 km or so is widely remarked, moreover. In Fig. 6, shown above is a cross-section by Van Mieghem based on a series of consecutive soundings at Uccle, Belgium, and a few nearby stations, shows a very shallow cold air tongue and an open warm sector, vdth the accompanying clouds, surface and stratosphere weather changes. The typical multiple tropopauses and stratosphere changes are present but not nearly so pronounced as over a deep cyclone. The surface weather follows a very ideal course according to the original Bjerknes scheme of 1919. [Dotted lines are inversions of subsidence (in the troposphere) and diffuse tropopauses (at high Mem. Inst. Roy. Met. levels) ; temp, in degrees Abs.; clouds stippled.] (From: Belg., V. 12, 1939.) . ;

176 AIR MASS ANALYSIS

A BIBLIOGRAPHY FOR SYNOPTIC METEOROLOGISTS

By Robert G. Stone

This is by no means exhaustive but it includes most of the more important and recent papers. We give some leads to literature of the many phases of meteorology which impinge on the theory or practice of analysis and forecasting in all parts of the world. "Synoptic papers" become out of date so rapidly that only the recent literature is useful to any great extent; the earlier ones listed are either classics still of great intrinsic worth or else notable historical milestones. For English speaking countries, however, and particularly the United States, many papers of local interest are added. American synoptic meteorology emphasizes the use of upper air soundings, i.e., direct aerology, for which it is supplied with the greatest radiosonde network in the world; whereas over most of the remainder of the globe only an "indirect aerology" can be practiced. We have included representative literature in that art. It will be understood that the authors of the various articles in this booklet do not agree with all the views one can find in these references. Furthermore, most synoptic meteorologists modify their views and practices considerably from to time in the light of new data and experience, a fact which the student should keep in mind when reading all but the latest papers. The unorthodox classification of the literature used here is based solely on cognate fields of special interest to practical and research workers in synoptic meteorology in English speak- title only once, that being under ing countries ; there is no cross referencing and each appears the subject for which it now appears to have the most intrinsic value, regardless of the claims of the title or intention of its author. Many theoretical papers bearing on analysis are included popular work is omitted. Selection has been exercised to exclude most ephemeral matters in rapidly changing subjects, but some old or superficial analyses contain valuable illustrative data for the student. Before using the bibliography study the annotated headings below.

A. GENERAL WORKS: TEXTBOOKS; HANDBOOKS; TREATISES

1. General Meteorology (Physical and Synoptic)

2. Synoptic Meteorology

3. Dynamic Meteorology; Hydrodynamics

4. Special Fields of Meteorological Physics

5. Revolving Storms of Special Types

Some of the more important books and papers on small vortices, waterspouts, tornadoes, whirlwind, dust devils, tropical hurricanes, typhoons, etc., from the dynamic and synoptic point of view; some papers on "dust storms" included though they are not usually vortical (see also under Section G. )

B. METEOROLOGICAL PHYSICS (RADIATION; OZONE; ICING)

Only a few of the summary and more valuable references, in which further bibliography icing, glaze, etc., appear under Sect. G. will be found ; some purely synoptic papers on aircraft

C. STATICS, DYNAMICS, AND FLUID MECHANICS APPLIED TO THE ATMOSPHERE; THEORIES OF CYCLONES AND ANTICYCLONES

Theoretical papers which have either been of great influence in synoptic meteorology, or contain useful analysis of meteorological data, or which give the background for certain practical methods now current. The literature of this sort is rather thoroughly covered between the standard works by Shaw, Ertel, Bjerknes, Koschmieder, Exner, Brunt and Hann-Suring, changes, but a selection is given here of the more important and later papers on pressure perturbations, the general circulation, turbulence and energy exchange, flow patterns, particularly from the leading schools of thought now influential. More on turbulence and radiation H, will be found under Sections B and H. Some model experiments are cited (see also D 2, and J). BIBLIOGRAPHY 177

D. THE STATISTICAL AND SCHEMATIC BACKGROUND FOR SYNOPTIC PRACTICE:

1. Mean (General) Circulation a. Surface Data b. Aerological Data In this group are chiefly statistical materials to which some interpretation is given ; mere tabular results are not listed except for some remote regions where they are scarce and of special value to synoptic workers. The work by Wagner (1930) and Shaw's "Manual", vol. 2, give adequate bibliographies and summaries of the published aerological data for the world. The distinction between surface and aerological data is often arbitrary, but under (b) are found only discussions of direct upper-air observations, while under (2) appear both climatological (surface) data and indirect deductions on the upper air. Discussions of the statistics according to moving pressure systems are under D 2, but such often contain material for

the general circulation, hence is is well to refer to that Section also ; likewise see D 3. Also some papers under C contain incidental material for this category Ceilings, mean lapse rates, wind roses and resultants, upper mean-pressure maps, mean humidity aloft, and mean circulation patterns aloft.

2. Average Structure and Movement of Cyclones and Anticyclones; Models

The distinction between this and Sections C, G and D 1 is sometimes arbitrary ; however, papers devoted primarily to statistical average conditions at the surface or aloft in cyclones and anticyclones, to the average or most frequent tracks of same (whether direct or indirect observations) are included here, while incidental information of this kind appears in many papers under the other sections mentioned. A few discussions of one or more situations

selected or advocated as typical of pressure systems in general or for a given region ; all schematic or model structures (some papers on typical isobaric maps appear under E), and

correlations of pressure, temperature and w^inds aloft, find their place here. Also : structure of fronts and inversions, vorticity and solenoid distribution, symmetry points, microbaric waves, isallobaric fields, gradient vrinds, etc.

3. Air Mass Properties and Correlations Statistics of air-mass properties by air-mass types, or by wind directions (see also D 1

and D 2 ) , their frequencies, geographical ranges, sequences, effects on climate, and correlations with other geophysical phenomena and the weather type ; air mass and frontal climatology. E. SPECIAL AIDS TO ANALYSIS AND FORECASTING

1. Charts, Rules, Tschniques, Thermodynamics, Formulae, Nomograms, Tables. 2. Kinematic Methods

This is a potpourri to call the attention of the student and practicing synoptic meteorologists to various aids and methods of analysis of proven or probable practical value, including diagrams, nomograms, rules for forecasting, etc. However, rnuch ephemeral material of this sort is omitted, such as codes, obsolete principles, futile "tricks", etc. Some of the better examples of empirical statistical forecasting, indirect aerology over the oceans, and aviation their reduction and problems are included ; For the technique of aerological measurements and evaluation, see the instruction handbooks of the national weather services or Linke's "Mete- orologisches Taschenbuch".

F. HISTORICAL FORERUNNERS OF FRONTAL ANALYSIS

G. DETAILED ANALYSIS OF SYNOPTIC SITUATIONS

1. North and Central America 2. North Atlantic and Caribbean 3. North Pacific 4. Southern Hemisphere 5. Europe 6. Asia and Asia Minor 7. Africa (North of the Equator)

The regional and chronological divisions are for convenience primarily : —1928 marks the appearance of Bergeron's "Dreidimensional Wetteranalyse", 1937 the transition to isentropic analysis (U. S.), and 1935 to the use of divergence principles (Germany), as well as to the introduction of radiosondes, with a resulting general modification of purely Bergeronian synoptics (indirect aerology) towards direct methods. For tropical regions the papers on the general circulation (Sect. D 1) and on revolving storms (Sect. A 5) should be considered as part of the present category as well. (For mere descriptions of weather phenomena see works on general meteorologv). For U. S.. Germany, and Russia, where aerological data are regularly available, mostly only the studies based on more or less upper-air analysis are included. (Outline continued, next page) 178 AIR MASS ANALYSIS

H.—METEOROLOGY OF THE FRICTION LAYER

1. Turbulence

2. Surface Temperature Influences

3. Mountain Meteorology

4. Micro-Aerological Analysis and Microclimatology ^

Except for some purely theoretical items in Sect. C and A3, all the papers selected dealing with the thermal and frictional influences of the earth's surface are grouped here for convenience of the many meteorologists who are specially interested in them. Otherwise these would belong to sections B, C, D, G, or I. The distinctions between "turbulence", "mountain meteorology", and "micro-aerology" cannot be made generally except from some particular point of view, which here is essentially a practical rather than a physical one. "Turbulence" covers wind structure, eddy viscosity, Austausch, evaporation, etc., over level surface or small obstruc- tions, both in theory and in measurements to check theory or for aviation, etc. Many more references will be found in Lettau's "Atmospharische Turbulenz" and in works on Aerody- namics and Hydrodynamics (Sect. A3). "Mountain Meteorology" covers large-scale turbulence and special winds due to hills and mountains, as well as the departures of mountain observations from free-air conditions and the adaptation of mountain observations in synoptic or dynamic meteorology. "Micro-aerology" includes the actual observations of air structure (synoptic and average) in layers close to the ground to show surface influences, radiation, etc. Turbulence measurements are chiefly listed under that heading, however. "Micro-climatology" provides data on representativeness of surface weather reports and the mean circulation in the lowest layers ; it is a valuable link in the application of synoptic meteoroogy to many practical ploblems.

I. PRECIPITATION AND CONDENSATION; CONVECTION; CLOUDS; STRATUS AND FOG

No attempt has been made to separate these topics as they intergrade and the number of citations is not inconveniently great. Only recent and summary papers on condensation and precipitation theory are cited (see also Sect. B., and A 4). "Convection" is here restricted to vertical convection from surface heating, and convergence, lifting, etc., resulting in instability and clouds, with applications to gliding, aviation, weather analysis and forecasting. The theory of lapse rates and of the kinetic energy of thermal stratifications is partly covered in Sections A, C, and E. Of the large literature on clouds some of the best aerological studies sort will and synoptic applications have been- selected ; much further valuable material of this be found incidentally in Sections B, D, E, G, and notably Siiring's book gives further bibliography, especially on other aspects of clouds.

J. INSTRUMENTAL PROBLEMS AND DEVICES

Improvements in aerological instruments come so rapidly that only late work is of much practical value except to specialists in instruments. The instruction handbooks issued by the weather services of each country should be consulted for the national and official practices, which vary greatly. See also Sect. E 1, B, and C.

Abbreviations

The following condensed abbreviations are used. Other abbreviations are more complete and will probably be recognized at sight.

Ann. d. Hydr. Annalen der Hydrographie und maritimen Meteorologie, Berlin. BAMS Bulletin of the American Meteorological Society, Milton, Mass. Beitr. Phys. fr. At. Beitrage zur Physik der freien Atmosphare, Leipzig. Geog. Ann. Geografiska Annaler, Stockholm. Geofys. Publ. Geofysiske Publikasjoner, Norske Videnskaps Akademie, Oslo. Gerl. Beitr. Geophys. Gerlands Beitrage zur Geophysik, Leipzig. Met. Mag. Meteorological Magazine, London. MWR, or M. W. R. Monthly Weather Review, Washington. MZ, or M. Z. Meteorologische Zeitschrift, Braunschweig. QJRMS, or Q. J. R. M. S. Quarterly Journal of the Royal Meteorological Society, London. UGGI Union Geodesique et Geophysique Internationale. )) ,

BIBLIOGRAPHY 179

A. GENERAL WORKS; TEXTBOOKS, HANDBOOKS, TREATISES

1. General Meteorology (Physical and Synoptic) ANGOT, A., Traits de meteorologie, (4th ed. HABERMEHL, R., (editor), Handbuch der rev. by Brazier), Paris, 1928. Fliegerwetterkunde. Berlin, 1938-40. 4 vols. [Various authors ; deals with instruments, BEZOLD, A. von, Gesammelte Abhandlungen principles and methods used in the German aus den Gebieten der Meteorologie und Erd- weather service.] magnetismus, Braunschweig, 1906, 448 pp. HANN-SiJRING, Lehrbuch der Meteorologie, BRUNT, D., Physical and dynamical meteor- 5th edition, v. 1, Leipzig, 1937-39 ; v. 2 in orology, London, MacMillan Co. 1939, 2nd progress. [The leading reference handbook, ed. very comprehensive and authoritative.] BYERS, H. R., Synoptic and aeronautical me- Taschenbuch, teorology, McGraw-Hill, N. Y., 1937, 279 pp. LINKE, F., Meteorologisches Ausgabe 1-4, Leipzig, Akademische Verlags- Review in B. A. M. S., June, 1938. (Good 1 (316 general text. gesellschaft M. B. H. Ausgabe p.) 1931; Auss- 2 (336 p.) 1933; Ausg. 3 (268 Weather, York, CLAYTON, H. H., World New p.) 1939; Ausg. 4 (286 p.) 1939; Ausg. 5, 1923, 393 p. 1939. [Ausg. 3-5, are a new edition of Ausg. CONRAD, v.. Die klimatologischen Elemente 1-2] und ihre Abhdngigkeit von terrestrischen ROYAL Meteorological Society, Some prob- der Klimatologie, Band Einflilssen, Handbuch lems of modern meteorology, London, Royal 556 Berlin, Gebriider Borntra- 1, Teil B, pp. Met. Soc, 1934, 170 p. eger, 1936. [Standard handbook on variation of climatic and weather elements with SHAW, S., The Air and its ways. University time, elevation, latitude, etc.—an indispens- Press, Cambridge, 237 pp., 1923. able reference and valuable bibliographic SHAW, W. N., Manual of Meteorology, Lon- aid.] don, MacMillan Co. 4 Vols, (see esp. Vol. COYECQUE, M., Notions de meteorologie ge- 11, 1936, Vol. Ill, 1930, Vol. IV, 1931.) nerale et nautique, 2nd ed., Paris, 1931. SPRUNG, A., Lehrbuch der Meteorologie, 1885, 407 DINES, W. H., Collected scientific papers, Hamburg, p. London, Roy. Met. Soc, 1931. SuRING, R., Leitfaden der Meteorologie, Leip- zig, 1927. FERRAZ, J. de Samp., Meteorologia Brasileira, Bibliotheca Pedagogica Brasileira, Brasiliana, U. S. Dept. of Agric, 1941 Yearbook of Agri- Serie 5, vol. 33, 588 pp., 1934. (General culture : Climate and man. Part 1, Section Meteorology. 7, The scientific approach to climate and

weather, 80 pp. ; Part 1, Section 9, Weather FICKER, H. von, Meteorologie, in Miiller-Pouil- forecasting, 40 pp. lets' Lehrbuch der Physik. 11th Ed., Bd. 5, 1st Hf., Physik der Erde, Braunschweig, ZOCH, R. T., A brief list of works on meteor- 1928, pp. 1-170. ology, MWR., 68, pp. 1-3, 1940.

2. Synoptic Meteorology

BAKALOW, D., GrundzUge der Synoptischen CHROMOV, S. P., iJvod do Synoptickeho Roz- Wettervorhersage (in Bulgarian), Sofia, boru Pocosi, Praha, 1937. 492 p. [Chechslo- 1938. vakian transl. of Chromov's Introd. to Syn- optic Analysis, 2nd ed.] BERGERON, T., Hur vddret blir till och hur det forutsdges, Ymer, H. 2-3, 1937, pp. DeDeBANT, G., and A. VIAUT, Manuel de 191-231. meteorologie du pilote, Paris, 1936, 194 P. [French practice, with emphasis on indirect BERGERON, T., Lektsii ob Oblakakh i Prak- ticheskom Analize Karty (Lectures on clouds aerology.] Wettervorhersage, and on the practical analysis of the map ) DEFANT, A., Wetter und Moscow, 1934. 154 pp., (read in 1932 at Leipzig und Wien, Franz Deuticke, 1918. the Central Weather Bureau, USSR, trans- 290 p. lated from the German manuscrift under the EREDIA, F., Aerologia e Meteorologia. editorship of S. P. Chromov). Caserta, Italy, 322 pp., 1935. BERGERON, T., The Physics of Fronts GEORGII, W., Flugmeteorologie, Leipzig, 1927, (English abstract of Pt. II of "uber die 237 pp. dreidimensional Verkn. Wetteranalyse," GEORGII, W., Wettervorhersage, Dresden, planographed, the author, 1936 full 1928), 1924, 114 pp. paper to appear later in Geophys, Publ.] Re- Occlusions, QJRMS., printed in BAMS, v. 18, pp. 265-75, 1937, GOLD, E., Fronts and 107-158. [A history and and in Das Wetter, Dec. 1936. V. 61, 1935, pp. summary of the subject.] T., Trechermo svjasnij sinopti- BERGERON, GREAT BRITAIN, Hydrographic Dept., Ad- // [Part 2 of the "Dreidi- cheskij analis— miralty weather manual, London, 1938. mensional verknupfende Wetteranalyse", not published in full yet in any other language, GREGG, W. R., et al. Aeronautical Meteor- but in abstract as "The Physics of Fronts".], ology, 2nd ed. N. Y., 1930, 405 pp.

192 pp ; Central Off., Hydro.-Met. Serv., JORDANOFF, A., Through the overcast: the USSR, Moscow, 1934. weather and the art of instrument flying. 356 1938. BERGERON, T., Uber die dreidimensional Funk and Wagnalls, N. Y., pp., but vivid illustr.] verknupfende Wetteranalyse. Teil I. Geofys. [Popular, Publ., V. 5, No. 6, Oslo, 1928, [The chief MeZIN, M., Cours de frontologie, Paris, Off. original work on Norwegian methods.] Nat. Met., 2 vols., 1936. CHROMOW, S. P., EinfUhrung in die Wetter- MIEGHEM, J. VAN, Prevision du temps par analyse, Moscow, Central Office of the Hy- I'analyse des cartes meteorologigues. Inst. dro-meteorological Service, 2nd, ed., rev. and Beige de Recherches Radioscientifiques, v. 6, eni., 510 pp., 1937. Paris, 1936, 138 pp. ) .

180 AIR MASS ANALYSIS

NOTH, H., Wetterkunde fur Flieger und pp. (with suppl. note by R. G. K. Lempbert: Freude der Luftfahrt, 2nd ed., Berlin, 1934. Sixteen years progress in forecasting PETTERSSEN, S., Weather Analysis and weather ) Forecasting. McGraw-Hill Co., N. Y., 1940, SUTCLIFFE, R. C, Meteorology for aviators, 502 pp. London, Met. Off., 1939. REICHELDERFER, F. W., Revort on Nor- SWOBODA, G., Flugmeteorologie und Flugwet- wegian Methods of Weather Analysis, U. S. terdienst, Prag, 1938 [In Checkoslovakian]. Navy Dep't., Bur. of Aeronautics, 1932, (Corrections, 1935) mimeog., 45 pp. TAYLOR, G. F., Aeronautical Meteorology, N. Y. Pitman Publ. Co., 1938, 429 pp. SCHINZE, G., Die praktische Wetteranalyse, Aus dem Archiv der Deutschen Seewarte, U. S. ARMY, AIR CORPS, Primary Flying Bd. 52, Nr. I, 72 pp. 1932. School, Randolph Field, Texas, Department SCHINZE, G., Untersuchungen zur aerologis- of ground instruction. Weather Manual for chen Syiwptik, Breslau- Krietern, 1981, and Pilots, 2nd ed., March 1940, 69 p. Hamburg, 1932. U. S. ARMY, Office of the Chief of the Air SCHMAUSS, A., Das Probleme der Wettervor- Corps, Training Guides Meteorology. 2 Vols. hersage, 2nd ed., Leipzig, 1937. 102 p. Rev. ed. 1938, 267 pp. [Philosophical rather than practical.] WEIGHTMAN, R. H., Forecasting from syn- SHAW, N., Forecasting weather. London, optic weather charts, U. S. Dept, Agric. Constable and Co., 1911, 3rd ed., 1940, 644 Misc. Publ. 236, 2nd edition, 1940.

3. Dynamic Meteorology; Hydrodynamics

ABBE, C, The mechanics of the earth's at- EXNER, F., Dynamische Meteorologie, 2nd mosphere. A collection of translations. 2nd ed., Vienna, 1925 [Standard work.] coll., Inst., Washington, Smithson. 1891 ; NATIONAL METEORO- 3rd coll., Washington, Smithson. Inst., 1910, FRANCE. OFFICE meteorologie dynami- 617 P. [Contains the classic papers of Helm- LOGIQUE, Cours de — noyaux de variation de pression, holtz and Margules, etc., translated into que Les English.] Paris, 1936. ANSEL, A., Beitrdge zur Dynamik und Ther- GOLDSTEIN, S., (ed.). Modern developments m.odynamik der Atmosphdre. Dissertation in fluid dynamics, Oxford, 1938. 2 vols. Gottingen, 1913, 67 p. 686 pp. ARAKAWA, H., [Dynamical Meteorology'^, in KOSCHMIEDER, H., Dynamische Meteorolo- Japanese, Tokyo, 1940, 132 p. gie. Leipzig, 1933, 376 pp. BJERKNES, v., and others. Dynamic meteorology and hydrography. Washington, Car- LAMB, Horace, Htjdrodynamics. 6th. ed., Cam- bridge, Univ. Press, 1932. 738 p. negie Inst., 1910. Vol. I, Statics ; Vol. II, is to Kinematics ; Vol. Ill, Dynamics, yet LETTAU, H., Atmosphdrisches Turhulenz, appear. Vols I and II pub'd. in German, Leipzig. 1939. [Very comprehensive treatise, Braunschweig, 1912-13. with bibliography.] BJERKNES, V, and others, Physikalische Hy- drodynamik mit anwendung auf die dyna- PRANDTL, L., and Tietiens, Hydro- und Aero- mische Meteorologie, Berlin, J. Springer, mechanik, Berlin. Bd. I, 1929, 238 p. Bd. 1933. 797 pp. (Great work; includes, pp. n, 1931, 299 p. 672-779, a treatment of dynamic meteorology mechanics viscous general circulation, PRANDTL, L., The of w^ith applications to the Durand. Aerodynamic The- as developed by the Bergen School) (French fluids In W. F. Berlin, 1935, v. 3, Dw. G., pp. 34-207. transl., see next. ory, BJERKNES, v., J. Bjerknes, H. Solberg, and STiJVE, G., Thermodynamik der Atmosphdre; T. Bergeron, Hydrodynamique Physique, 3 Dynamik der Atmosphdre; Die atmospha- vols., Paris, 1934, (French transl. of Phys- rische Zirkulationen. 420 pp. Berlin, 1937. Lief. ikalische Hydrodynamik). (Handbuch der Geophys ; Bd. IX, 2)

DEFANT, A., Statik und Dynamik der At- A., Thermodynamik der Atmos- heraus- WEGENER, mosphdre, in Handb. d. Exp.-Physik phdre, Leipzig, 1911. [Classic work, still geg. von und F. Harms, Leipzig, W. Wien valuable; 1911 ed. is better than 2nd ed., 1928, Bd. 1. Teil, 71 25, pp. 1936.] ERTEL, H., Methoden und Probleme der dynamischen Meteorologie, Berlin, 1938, 122 WILLETT, H. C, Dynamic Meteorology, Na- pp. [Mathematical emphasis.] tional Res. Council, B. 79, pp. 133-233, 1931.

4. Special Fields of Meteorological Physics

FARADAY Society, Disperse systems in gases; meteorological problems.] dust, smoke and a general discussion, fogs LANDSBERG, H., Atmospheric condensation 1300 pp., 1936. nuclei, (Band 3, Ergebnisse der kosmischen FLEMING, J. A., and others, Terrestrial Physik, Leipzig, 1938, pp. 155-252.) magnetism and electricity. (V. 8 of "Physics W. E. K., Visibility in mete- of the Earth", Nat. Res. Council.) N. Y., MIDDLETON, orology, Toronto, 1935, 104 pp. 1939. [Comprehensive and authoritative.] HAURWITZ, B.,The physical state of the PLANCK, M., Treatise on thermodynamics, upper atmosphere. (Reprint of arts, from 3rd ed., London, 1927. Jn. Roy. Astron. Soc. Canada) Toronto, A., und A. Wigand, Das At- 1937. [bibliog.] 96 pp. SCHMAUSS, mosphdre als Colloid, Braunschweig, 1929. HUMPHREYS, W. J., Physics of the air, 2nd electricity, ed., N. Y., McGraw-Hill, 1929, 645 pp., 3rd. SCHONLAND, B., Atmospheric ed. 1940. [On physics applied to certain London, 1932, 100 pp. BIBLIOGRAPHY 181

5. Revolving Storms of Special Types ALGUe, J., Cyclones of the Far East, Manila, JEFFRIES, C. W. and G. S. P. Heywood, The 1904 [Still a great and valuable work.] law of storms in the China Sea, Append. 3, to 1937. 26 CLINE, I. M., Tropical cyclones, N. Y., Mac- Hong Kong Met. Results, pp. millan, 1926, 301 pp. KOSCHMIEDER, Staubsturme und Staubwan- COMBIER. R. P. CH., P. Gaubert, L. Petit- dem. Die Naturwiss., v. 27, pp. 113-22, 1939. jean, Vents de sable et pluies de boue, (bibliog). France, Office Nat. Met., Memorial, no. 27, 135 pp., 1937. KOSCHMIEDER, H., iJber Tornadoes und Tromben, Zusamm. Bericht., Die Naturwis- C. E., characteristics DEPPERMANN, Some senschaften, v. 25, pp. 657-664, 1937, [Bib- of Philippine typhoons, Philippine Wea. liog.] Bur., Manila, 1939. (abstr., BAMS v. 20, pp. 303-307, 1939.) LETZMANN, J., Experimentelle Untersuchun- gen an Luftwirbeln, Gerl. Beitr. Geophys., DEPPERMANN, C. E., Some comments on Bd. 34, pp. 130-172, 1931. Father Gherzi's "Constitution of typhoons", BAMS, V. 19, pp. 369-375, 1938. LETZMANN, J., Richtlinien zur Erforschung von Tromben, Tornados, Wasserhosen und DURST, C. S.. and R. C. Sutcliffe, The im- in : Publ. Secret, de portance of vertical motion in the develop- Kleintromben, No. 38 rOrgan. Met. Intern., Leyden, 91- ment of tropical revolving storms. QJRMS, 1939, pp. 110 (crit. by Kincer, 89-90.) V. 64, no. 273, pp. 75-84, 1938. (Add. note, pp.

id., p. 240 ; comment by Jeffreys, id., p. NEWNHAM, E. V., Mrs., Hurricanes and 336-S.) tropical revolving storms, London, Met. Office, Geophys. Memoirs, vol. 2, no. 19, EREDIA, F., La sabbia dell' atmosf era, Rivista pp. 229-333, 1922. di meteorologia aeronautica. An. 2, pp. 83- 99, 1938. NORMAND, C. W. B., On dust-raising winds, Dept. v. no. EXNER, F. M., ijber die Bildung von Wind- India Met. Memoirs, 22, 7, pp. hosen und Zyklonen S.-B., Akad. Wiss., 575-581, 1913. Wien, Ila, v. 139, 1923. NORMAND, C. "W. B., Recent investigations EXTERNBRINK, H., Zur Entstehung westin- on structure and movement of tropical storms in Indian seas. Gerl. Beitr. Geophys., discher Orkane. MZ, v. 55, Sept. 1938, 317- 233-243, 1931. 320, 1938. Bd. 34, pp. K. R., Soundings tem- FLOWER, W. D., Sand devils, London, Met. RAMANATHAN, of perature and humidity in the field of a office. Prof. Notes, no. 71 (v. 5), pp. 3-16, 1936. tropical cyclone and a discussion of its structure, India Met. Dept., Memoirs, v. 26, S., the growth FUJIWHARA, On and decay pt. 5, pp. 79-92, 1936. of vortical systems, QJRMS, v. 49, pp. 75- M., tropical vs. extratrop- 118, Apr. 1923. RODEWALD, On ical cyclonic structure, BAMS, v. 19, pp. GAIGEROV, S- S., Synoptic conditions accom- 339-341, 1938. panying tornadoes in the United States dur- SCHUBART, L., Praktische Orkankunde, Ber- ing 1884, BAMS, V. 21, pp. 229-236, 1940. lin, 1934. GHERZI, E., On the Constitution of Typhoons. SUTTON, L. J.. Haboobs, QJRMS, v. 57, no. BAMS V. 19, pp. 59-66, 1938. 239, pp. 143-162, 1931. HANKIN, E. H., On dust-raising winds and N., Travel of circular depressions and descending currents, India Met. Dept., SHAW. tornadoes, and relations of pressure to Memoirs v. 22, no. 6, pp. 565-573, 1913. winds for circular isobars. Geophysical Mem- HARMANTAS, L., Extracts notes de- from oirs, no. 12, M. O., no. 220b ; abstr. QJRMS, rived from synoptic mavs and flights in, the Oct., 1918, pp. 290-294 ; rev'd. Met. Mag., Manila-Guam Sector, BAMS, v. 20, pp. 301- 1918, pp. 61-64. 303, 1939. TAKAHASI, K., Distribution of various ele- HORIGUTI, Y., Note on the distribution and ments in a typhoon, Jn. Met. Soc. Jap., v. the motion of the clouds in the area of 18, no. 4, 1940, p. (13). typhoon, Kobe, Imp. Marine Obsy., Memoirs, TANNEHILL, I. R., Hurricanes, their nature V. 5, 1932-1935, pp. 25 40. and history, Princeton, Univ. Press, 1938, HORIGUTI, Y., On the Typhoon of the Far 257 pp. East. Part 4. The Distribution of the Orientacion en los Es- atmospheric pressure in the tynhoon area. VASQUEZ, E., Nueva tudios Ciclonicos. Naturaleza de las Rachas The movem.ent of the typhoon. Kobe, Japan, Ciclonicas, Havana, Obs. de Golegio de Imp. Marine Obs. Memoirs, v. 3, no. 3, pp. 1940, 65 127-148, 1928. Montserrat, pp. VERYARD. R.. Dust devils. Met. Mag., vol. HUBERT, H., Sur la distribution des filets 268, 1934. d'air dans les cyclones tropicaux, Annal. de 69, p. Phys. 6n Globe, No. 4, pp. 97-104, 1934, WALKER. G. T., On the mechanism of torna- (Indo China). does, QJRMS, V. 56, pp. 59-66, 1930. HURD, W. E., Waterspouts, M. W. R., v. 56, WEGENER. A., Wind und Wasserhosen in pp. 207-11, 1928. Europa, Braunschweig, 1917. B. METEOROLOGICAL PHYSICS (RADIATION; OZONE; ICING) ASHBURN, E. V., Radiation transfer in at- to Algeria and to California. Smithsonian 1 mospheric temperature inversions, BAMS, Inst.. Washington, pp. 77-86 ; Appendix V. 21. no. 5, pp. 205-206, 1940. by W. R. Blair; and W. R. Gregg, Free-air and Au- aNGSTRoM, Anders, Messungen der ndcht- data in southern California. July 191S, 107-147, 1915. lichen Ausstrahlung irn Ballon, Beitr. z. gust, pp. Phys. d. fr. Atm., Bd. 14, pp. 8-20, 1928. BALLARD. J. C, Some outgoing-radiation ANGSTRoM, A., A study of the radiation of and surface-temperature measurements at the atraosphere based upon observations of Fargo. No. Dak., Trans. Amer. Geophys. the nocturnal radiation during expeditions Un., 1937, Pt. I, pp. 127-30. 182 AIR MASS ANALYSIS

BROOKS, F. A., C. Lorenzen, Jr., and L. M. HRUDLICKA, B., Zur Nebelfrostfrage, Gerl. K. Boelter, Observations of nocturnal win- Beitr. Geophys., v. 51, pp. 335-342, 1937. ter atmospheric radiation in California, [Bibliog.] BAMS, V. 20, pp. 433-439, Dec. 1939. LANGE, Karl O., Vereisungsmessungen mit BRUNT, D., Some phenomena connected with der Harvard-Radiosonde. Beitr. z. Phys. d. the transfer of heat by radiation and turbu- fr. Atm., Bd. 25, pp. 241-250. 1939. In lence in the lower atmosphere, Roy. Soc, English in J. Aero. Sci., v. 6, Dec. 1938, Proc, A, V. 130, pp. 98-104, 1930. pp. 59-63. BRUNT, D., Notes on Radiation in the at- LEJAY, P., Ozone measurements and cur- mosphere, QJRMS, V. 58, 1932, p. 389-417 rents in the stratosphere BAMS, v. 20, pp. (See also his "Physical and Dynamical Me- 298-301, 1939. teorology.") McNEAL, D., [Aircraft] Ice formation in the BRUNT, D., Radiation in the atmosphere, atmosphere, J. Aero. Sci., Jan. 1937, pp. QJRMS, V. 66, Supplement, pp. 34-40, 1940. 117-123. BuTTNER, K., Strahlungsversuche im Flug- MINSER, E. J., Meteorological conditions zeug, Beit. Phys. fr. At., Bd. 16, H. 2, pp. associated with aircraft lightning discharges 156-162, 1929. and atmospherics, J. Aero. Sci., Dec. 1939,

51-55 ; v. 1940, 200-202. BYERS, H. R, Meteorological Aspects of pp. BAMS 21, pp. thunderstorm electricity, BAMS, v. 20, 1939, MoLLER, F., and R. MiJGGE, Gesante und p. 181-6. zonale ndchtliche Gegenstrahlung als Mittel zur Gewinnung aerologischer Aufschliisse, CHIPLONKAR, M. W., Measurements of at- z. Phys. d. f. Atm., Bd. 220- mospheric ozone at Bombay, Indian Acad. Beitr. 20, pp. 233, 1933. Sci., Proc, V. 10, no. 3, pp. 105-120, 1939. F., Die Wdrmequellen in der freien COBLENTZ, W. W., Circulation of ozone in MoLLER, Atmosphare, MZ, Bd. pp. 408-412, 1935. the upper atmosphere, BAMS, v. 20, pp. 52, 92-95, March, 1939. NOTH, H., Die Vereisungsgefahr bei Flug- Aeron. Obs., CONFERENCE on atmospheric ozone held at zeugen, Lindenberg, Preuss. wiss. Bd. 16, 1930, Oxford, Sept. 9-11, 1936. Papers read at the Arbeiten. Abhand., pp. Conference, QJRMS, Suppl. to v. 62, 76 pp., G1-G12. 1936. PEKERIS, C. L., Atmospheric ozone as a pos- no. ELSASSER, W. M., An atmospheric radiation sible meteorological factor, BAMS, v. 20, 1-10, Jan., 1939. chart and its use, QJRMS, v. 66, Supple^ 1, pp. ment, pp. 41-56, 1940. PEKERIS, C. L., The development and pres- the theory the heat balance ELSASSER, W. M., Is radiative cloud cooling ent status of of Mass. Inst. Tech., Met. a significant phenomenon in the atmos- in the atmosphere, Course, Prof. Notes, no. 5, 1932, 80 p. phere? BAMS, V. 21, pp. 202-205, 1940. [Excellent review ; bibliog.] ELSASSER, W. M., A new graphical method O., Beitrdge zuni Vereisungs- for the determination of radiative heat REINBOLD, der Luftfahrt, MZ, Bd. 52, pp. 49- transfer in the atmosphere, BAMS, v. 20, problem pp. 402-404, 1939. 54, 1935. SIMPSON, G. C, Ice accretion on aircraft, FREY, A., Zur Enstetung des Hagels, Gerl. London, Met. Office, Prof. Notes, no. 82 216-222, 1937. Beitr. Geophys., Bd. 50, pp. (v. 6), pp. 3-14, 1937. Partly repr. BAMS, GISH, O. H., and K. L. Sherman, Meteor- V. 19, pp. 326-329, 1938. ological features indicated by air-conduct- STICKLEY, A. R., Some remarks on the ivity measurements made on flight of Ex- physical aspects of the aircraft icing prob- plorer 11, Trans. Amer. Geophys. Union, lem. J. Aero. Sci., Sept. 1938, pp. 442-446. 1936, pt. 1, pp. 152-156. TANCK, H.-J., Die tdgliche Erwdrmung der der Absorption der GOLDSCHMIDT, H., Strahlungsmessungen Atmosphare infolge Sonnenstrahlung durch den at- auf FreibaUlonfahrten, MZ, Bd. 52, pp. 125- direkten Ann. der Hy- 129, 1935. mosprdrischen Wasserdampf, drog., Bd. 68, h. 2, pp. 47-64, 1940. HALLANGER, N. L., Study of aircraft icing, A., et M. E. Vassy, Etude de I'ozone BAMS, V. 19, pp. 377-381, 1938. VASSY, dans ses rapports avec la circulation atmos- HAND, I. F., Review of solar radiation in- pherique. La Meteorologie, jan.-fev., 1939, vestigations of the U. S. Weather Bureau, nn. 316. V. 415-41, (bibliog). MWR, 64, 1937, p. VIAUT, A.,ttude sur le givrage. La Meteoro- mai-juin, 158-186. HAURWITZ, B., Atmospheric ozone as a con- logie, 1939, pp. stituent of the atmosphere, BAMS, v. 19, WINTER, Heinrich, Untersuchungen iiber Glat- pp. 417-424, 1938. teisbildung, MZ, Bd. 53, pp. 63-68, 1936. C. STATICS, DYNAMICS, AND FLUID MECHANICS APPLIED TO THE ATMOSPHERE; THEORIES OF CYCLONES AND ANTICYCLONES AHLBORN, Die drei grossen Zirkulationen cyclones. Geophys. Mag., Tokyo, v. 10, no. der Atmosphare, Beitr. z. Phys. d. fr. At., 1, pp. 43-66, 1936. Bd. 11, H. 117-153, 1924. 3, pp. Zyklonen BANERJI, S. K., On discontinuous fluid mo- und Antizyklonen im mechanismus der At- tion under different thermal conditions, In- mosphare, id., V. 12, 63-92. 1925, pp. dian J. Phys., V. 7, pt. 3, 1932. ARAKAWA, H., A further investigation on BAUR, F. und Philipps, H., Die Bedeutung the diffusion of vorticity, Geophys. Mag., der Konvergenzen und Divergenzen des Tokyo, V. 4, no. 2, pp. 113-116, 1931. Geschwindigkeitsfeldes fiir die Druckdv- derungen, Beitr. Phys. fr. At., Bd. 24, pp. ARAKAWA, H., On the development of gradi- 1-17, 1938. ent winds, Geophys. Mag., Tokyo, v. 7, pp. R., Zur Dynamik anisobarer Bewe 165-169, 1933. BECKER, gungen an Gleitflachen, Gerl. Beitr., v. 21, ARAKAWA, H., Theory of convection thun- h. 1, 1929 (cont. Beitr. Phys. fr. At., v. 16, dershowers, convection cyclones and anti- p. 169.) )

BIBLIOGRAPHY 183

BECKER, R., Zur Frage der Thermozyklo- BOYDEN, C. J., The mechanics of the de- genese durch aufgeprdgte stratosphdrische pressions: Some criticisms and a contribu- Druckdnderungen, Gerl. Beitr. Geophys., Bd. tion, QJRMS, v. 64, no. 273, pp. 85-94, Jan., 32. pp. 260-267, 1931. 1938. (Comments, id., p. 629-30.) BERSON, P. A., iJber die Beziehung der age- BROOKS, C. E. P., Some problems of modern ostrophischen Keymponente der Windgesch- tneteorology. No. 9 : The origin of anticy- windigkeit zum Isallobarenfeld, M. Z., Bd. clones, QJRMS, V. 58, no. 247, pp. 379-388, 56, H. 9, pp. 329-333, 1939. 1932. BJERKNES, J., La circulation atmospherigue BRUNT, D., The dynamics of Cyclones and da7is les latitudes soustropicales, Scientia, anticyclones regarded as atmospheric vorti- Feb. 1935, 20 pp. ces, Proc. Roy. Soc. Lond., A, v. 105, 1924, pp. 70-80 (cont. from: id., v. p. 397, BJERKNES, J., The deepening of extra-trop- 99, 1918). ical cyclones, QJRMS, v. 66, Supplement, pp. 57-59, 1940. BRUNT, D., Some problems of m,odern meteorology: 1. The present BJERKNES, J., Theorie der aussentropischen position of theories the origin Zyklonenhildung, MZ, Dec. 1937, pp. 462-66. of of cyclonic depressions,. QJRMS, July, Engl, transl., mimeogr., U. S. Wea. Bur., 1930, pp. 345-350 ; Repr. in 1939.) MWR, v. 58, no. 10, 1930, pp. 419-422. K. L., BJERKNES, J., The upper perturbations, Un. CALDER, A note on the constancy of Geod. et Geophys. Intern. 6ieme Ass. Gen., horizontal turbulent shearing stress in the Edimbourgh, Sept., 1936, Proces verbaux de lower layers of the atmosphere, QJRMS, v. 65, pp. 537-541, 1939. I'Assoc. de Met., part 2, Mem. et Disc, pp. 106-119. DeDeBANT, G., and Ph. Wherle, La definition de la turbulence, C. R. BJERKNES, J., and C. L. Godske, On the Acad. Sci. Paris, v. theory oj cyclone formation at extra-tropical 208, 1939, p. 625-628 ; also see v. 206, 1938, p. 1790-2; and J. de K. Feriet, bases Fronts, Astrophysica Norvegica, Vol. 1, No. Les de mecanique de la turbulence. Sciences, nov. 6, pp. 200-235, 1936. 1937, p. 372-82 ; and C. R. Acad. Sci., v. BJERKNES, J., et H. Solberg, L'tvolution des 208, p. 722-5; J. Aero. Sci., v. 7, no. 12, cyclones et la circulation atmospherique 1940, p. 518. d'apres la theorie du fro^it polaire, France, a., Beitrag Office, Nat. Met., Memorial, no. 6, pp. 83- DEFANT, Ein zur Theorie der 102. 1923. (Transl. of The life-cycle of cy- Polarfront, M. Z., Bd. 41, pp. 1-8, 1924.

clones. . . , Geofys. Publ. v. 3, no. 1. DEFANT, A., Primdre und sekunddre—freie BJERKNES, v., iJber einen hydrodynamischen und orzwungene Druckwellen in der Atmos- Fundamentalsatz und seine Anwendung, be- phdre, Oest. Zentralanstalt f. Met. u. sonders auf die Mechanik der Atmosphdre Geodyn., Festschr., 1926, pp. 83-103. und des Weltmeers, Kongl. Sv. Vet. Akak. DEFANT, A., Schwingungen einer zweifach Handlingar, Bd. 31, No. 4, 1898. (See later geschichteten Atmosphdre und ihr Verhdlt- papers. MZ, 1900, p. 97, 145; 1902, p. 96.) nis zu den Wellen im Luftmeer, Beitr. Phys. Mon. Wea. Rev., June 1900, p. 250, Oct. 1900, fr. Atmos., Bd. 12, 1925, H. 2, pp. 112-137. pp. 434-442, Dec. 532-535.) 1900, pp. New DOBSON, G. M. B., Winds and temperature proofs: Iswekow, J. Geophys. and Met. (Mos_ gradients in the stratosphere, QJRMS, v. 46, cow), V. 1, p. 195; and Lombardini, Atti pp. 54-64, 1920. Acad. Lincei, Rend., v. 15, 1932, p. 459 ; DiJBuCK, A. F., To the theory of high winds Ertel, Sityb. Preuss. Akad. Wiss., 1933 p. 447. distribution in the front region. Met. i Hy- drol., V. 1937, no. 4-5, pp. 17-27. BJERKNES, v., De I'application des theore- DURST, C. S., Convergence and divergence in mes de circulation a la discussion des pheno- the atmosphere, QJRMS., v. 66, 1940, p. 171- menes atmospherique s. Union Geod. et Geo- 80. phys. Intern., 6ieme Assemblee Gen., Sept., 1936, Proces verbaux de I'Ass. de Met. Part DURST, C. S., The Intrusion of air into anti- 2, Mem. et Disc, pp. 7-47. cyclones, QJRMS, V. 59, no. 250, pp. 231-237, July, 1933. BJERKNES, v.. Application of line integral theorems to the hydrodynamics of terres- EKMAN, V. W., Eddy-viscosity and skin-fric- trial and cosmic vortices, Astrophysica Nor- tion in the dynamics of winds and ocean- vegica, Vol. 2, no. 6, pp. 263-339, 1937. currents, Mem. Roy. Met. Soc, v. 2, no. 161-172, BJERKNES, v.. Die Atmosphdre als zirkula- 20, pp. 1928. (See also: Gerl. Beitr. rer Wirbel. Wellentheorie der Zyklonen und Geophys.. v. 36, 1932, pp. 385 ff.). Crit. by Antizyklonen. Ergeb. aerol. Tag. 1921, Son- Thorade, Ann. d. Hyd., 1929, pp. 113-115. derh. Beitr. z. Phys. d. fr. Atmos., 1922, pp. ERTEL, H., AUgemeine Theorie der Turbu- 5-37. lenzreibung und des Austausches, Sitz.- BJERKNES, v.. Die atmosphdrischen Storungs- Berich. preuss, Akad. Wiss., 1932, pp. 436- 445. gleichungen, Beitr. z. Phys. d. fr. Atm., Bd.

13, pp. 1-14, 1926 ; also Z. angew. Math. ERTEL, H., Die Artender Unstetigkeiten des Mech., Bd. 7, pp. 17-26, 1927. Windfeldes an der Tropopause, M. Z., Bd. BJERKNES, v.. On the dynamics of the cir- 53, pp. 450-455, 1936. cular vortex, Geoph. Publ., Vol. 2, No. 4, ERTEL, H., Der Einfluss der Stratosphdre auf 1921. die Dynamik des Wetters, M. Z., Bd. 48, BJERKNES, v., Le probleme des cyclones, J. 1931, pp. 461-503 [bibliog.]. de Phys. et le Radium, v. 6, pp. 321-330, ERTEL, H., Die Geschwindigkeitsverteilung 1924. im stationdren geostrophisch-antitriptischen BJERKNES, v., iJber die hydrodynamischen Windfeld und im stationdren Triftstrom bei Gleichungen in Lagrangescher und Eulers- variablem Turbulenzkoeffizienten als Eigen- cher Form und ihre Linearisierung filr das wertproblem, Ann. d. Hydrog., Bd. 62, pp. Studium kleiner Storungen, Geofys. Pub., 35-36, 1934. Bd. 5, Nr. 11. ERTEL, H., Die Kriimmung der Diskontinui- BJERKNES, v., and H. Solberg, ZeUulare tdtsfldchen in der Atmosphdre und im Tragheitswellen und Turbulenz, Oslo, Viden- Ozean, Preuss. Met. Inst., Bericht iiber die skapakad, Avhandl., v. 1, no. 7, 1929. Tatigkeit, 1930, pp. 147-153. .

184 AIR MASS ANALYSIS

ERTEL, H., Singuldre Advektion, M. Z., Bd. GODSKE, C. L., A simplified treatment of 53, pp. 280-284, 1936. some fluid oscillations, Astrophysica Nor- ERTEL, H., Stromfelddivergenz und Luft- vegica, v. 1., no. 5, pp. 169-197, May, 1935. druckdnderuvg, M. Z., Bd. 53, pp. 16-17, GODSKE, C. L., Die Storungen des zirkularen 1936. Wirbels einer homogen-inkompressiblen Fliis- ERTEL. H., Tensorielle Theorie der Turbulenz, sigkeit, Publ. Oslo Univ. Obs., Bd. 1, Nr. Ann. d. Hydro., Bd. 65, pp. 193-205, 1937. 11, 1934. ERTEL, H., Thermodynamische Begrundung GODSKE, C. L , iiber Bildung und Vernich- des Richardsonschen Turbulenzkriteriums, tung der Zirkulationsbewegungen einer Fliis- MZ, Bd. 56, pp. 109-111, 1939. sigkeit, Astrophysica Norvegica, v. 1, no. 2, ERTEL, H., ijbe?- die ernergetische Beeinflus- pp. 11-86, Nov., 1934. s^ing der Troposphdrc durch stratosphere Druchschwasskungen, Gerl. Beitr. Geophys., GODSKE, C. L., Zur Theorie der Bildung aus- Bd. 37, pp. 7-15, 1932. sertropischer Zyklonen, M. Z., Bd. 53, pp. 445-449, 1936. ERTEL, H., Wdrmeleitung und quasistatische Zustandsdnderungen in der Atmosphdre, GOLD, E., Change of potential energy of a Preuss. Met. Inst., Bericht iiber die Tatig- layer of air with change of lapse rate, keit, 1928, pp. 121-129. QJRMS, v. 62, pp. 129-131, 1936. ERTEL, H., Ziisammenhang von Druckdnder- GOLDIE, A. H. R., Discontinuities ungen und Beschleunigungen an Diskonti- in the atmosphere, Proc. Rov. Soc. Edinbg., v. 45, nuitdten, M. Z., Bd. 53, pp. 394-395, 1936. no. 2, pp. 213-229, 1925. ERTEL, H., Zusammenhang von Luftdruckdn- derungen und Singularitdten des Impids- GOLDIE, A. H. R., Waves at an approxi- dichtefeldes. Sitz.-Ber. d. Preuss. Akad. d. mately horizontal surface of discontinuity in Wiss., Berlin, Phys.-Math. KL, 1936, pp. the atmosphere, QJRMS, v. 51, July, 1925, 257-266. pp. 239-246. (See also Johnson, id., v. 55, 1929, p. 19-30.) ERTEL, H., and S. Li, Der Advektionsmechan- isnius der atmosphdrischen Druckschwan- GRIMES, A., The movement of air across the kungen, Zeit. f. Phys., Bd. 94, pp. 662-673, equator, Malayan Meteorological Service, 1928. Memoirs, No. 2, 14 pp., 1937. ERTEL, H., and S. Li, Die Berechnung der HALES, A. L., Thermal stability the lower Advektion, M. Z., Bd. 51, pp. 356-357, 1935. of atmosphere, London, Roval Soc, Proc, v. EVJEN, S., iiber Stauung von Luft in der 151, A., pp. 624-640, 1935. (See also Saku- freien Attnosphdre und Bewegung einer Mas- raba, Jn. Met. Soc. Jap., 1936, p. 116 (12).) senpartikel im Luftdruckfelde, Ann. d. Hydr., 1937, H. 4, pp. 145-154. HAURWITZ, B., Einfluss von Massendnderun- gen in grossen EXNER, F. M., Sind die Zyklonen Wellen in Hohen auf die vertikale Tem- der Polarfront oder Durchhrilche derselben? peraturverteilung, MZ, Bd. 44, pp. 253-260, 1927. M. Z., Bd. 38, pp. 21-23, 1921. (see also Wegener, id., p. 300-302.) HAURWITZ, B., The height of tropical cy- EXNER, F. M., Gravitationswellen in der At- clones and the "eye" of the storm, MWR, v. mosphdre, Vienna, Akad. Wiss., Sitzb., Bd. 63, 1935, p. 45-49. 138, II a. pp. 223-244, 1929. HAURWITZ, B., The oscillations of the at- EXNER, F., Grundzuege einer Theorie der mosphere, Gerl. Beitr. Geophysik, v. 51, pp. synoptischen Luftdruckveraenderungen, Sitz- 195-233, 1937. ber. Wien. Akad. Wiss. 2a, v. 115, 1906, p. HAURWITZ, B., On the change of wind with 1171 ; V. 116, 1907, p. 995 ; v. 119, 1910, elevation under the influence of viscosity in p. 697; MZ, 1908, p. 57. curved air currents, Gerl. Beitr. Geophys., EXNER, F. M.. Die thermische und die dyna- v. 45, pp. 243-267, 1935. mische Auffassung der Luftbewegungen, M. HAURWITZ, B., On the vertical wind distribu- Z., Bd. 39, pp. 73-79, 1922. tion in anticyclones, extratropical and trop- EXNER, F. M., iiber die Energieleistung von ical cyclones under the influence of eddy Zirkulationen und Sandstroms Gleitwirbel, viscosity, Gerl. Beitr. Geophys., v. 47, pp. MZ, Bd. 40, pp. 14-19, 1923. 206-214, 1936. EXNER, F. M., Ueber die Temperaturver- HAURWITZ, B., iiber die Anderung des teilung in vertikalen Zirkulationen, Beitr. Temperaturgradienten in Luftsdulen von Phys. fr. Atmos., Bd. 11, 1924, p. 101. endlicher Hohe bei vertikaler Verschiebung, EXNER, F. M., Zur Dynamik der Bewegungs- Ann. der Hydrog., Bd. 59, pp. 22-25. 1931. forrtien auf der Erdoberfldche. Ergebn. d. HAURWITZ, B.. Zur Theorie der Wellenbewe- kosm. Physik, Bd. I, Leipzig, 1931, pp. 373- aungen in hift und Wasser. Veroff. geophys. 445. Inst. Leipzig, 2. Ser., Bd. 5, Heft 1, 1931. FICKER, H. von, Zur Frage der "Steuerung" HAURWITZ, B., The interaction between the in der Atmosphdre, M. Z., Bd. 55, pp. 8-12, polar front and the tropopause, Roy. Soc. 1938. Canada, Trans., Sect. 3, v. 33, pp. 83-105, 1939 FUJIWHARA, S., Remarks on the transverse eddy viscosity in the atmosphere near the HAURWITZ, B., The motion of atmospheric earth's surface, Geophys. Mag., Tokyo, v. 3, disturbances. Jn. Marine Res., v. 3, no. 1, no. 3, pp. 127-129, 1930. 1940. pp. 35.50. FUTI, H., On the non-stationary atmospheric HELMHOLTZ, H. von. The energy of the bil-

currents, J. Met. Soc, Japan, v. 15, pp. 45- lows and the wind, in : Cleveland Abbe, 47, 1937. Mechanics of the earth's atmosphere, 2nd GODSKE. C. L.. Review of the theory of ex- collection, Washington, Smithsonian Inst., tra-tropical cjiclone formation, Un. Geod. et 1891, no. 7, pp. 112-129. Geophys. Intern., 6ieme Ass. Gen., Sept., HELMHOLTZ, H. von. Influence of viscosity on 1936, Proces verbaux de I'Ass. de Met., Part the general circulation of the atmosphere.

2, Mem. et Disc, pp. 48-60. in : Cleveland Abbe, Mechanics of the earth's BIBLIOGRAPHY 185

atmosphere, 2nd collection, Washington, MARGULES, Max., The mechanical equivalent Smithsonian Inst., 1891, no. 5, pp. 78-93. of any given distribution of atmospheric pressure, and the maintenance of a given HELMHOLTZ, H. von. On the theory of difference in pressure, in : C. Abbe, The winds and waves, in : Cleveland Abbe, mechanics of the earth's atmosphere, 3rd Mechanics the earth's atmosphere, 2nd of collection, Washington, Smithsonian Inst., collection, Washington, Smithsonian Inst., 1910, no. 23, pp. 501-532. 1881, no. 7, pp. 112-129. MARGULES, Max., On the energy of storms, HERGESELL, H., Hydrodynamische Grund- in : C. Abbe, The mechanics of the earth's gleichungen—allgemeine Betrachtungen, Arb. atmosphere, 3rd collection, Washington d. preuss. aeronaut. Obs. Lindenderg, Bd. Smithsonian Inst., 1910, no. 24, pp. 533-595. 15, 1926, pp. 155-162. (See also add. by: Emden, MZ, 1917, p.

393 ; Schmauss, MZ, p. 15 HESSELBERG, Th., fiber Reibung und Dis- 1917, 95, 1919, p. r Sandstrom, Arkiv f. Mat. Astr. v. sipation in der AtmosphUre, Geofys, Publ., Fys., 7, no. 30, 1912.) ; by Margules, MZ, 1906, p. Bd. 3, Nr. 5, 1926. 481. Cf., V. Bjerknes, MZ, 1917, p. 166. HESSELBERG, Th., Untersuchungen. Uber die M., ijfcer Gesetze der ausgeglichenen Bewegungen in MARGULES, Temperaturschichtung in statioyidrbewegter und in ruhender Luft, der Atmosphdre, Geofys. Publ., Bd. 5, Nr. MZ, 1906, pp. 243-254. 4 ; Beitr. z. Phys. fr. Atm., Bd. 12, pp. 141- 160, 1926. MARGULES, M., uber die Anderungen des vertikalen TemperaturgefdUes durch ISIMARU, Y., On the dissipation of the en- Zusam- mendruckung oder Ausbreitung einer ergy due to internal friction in the atmos- Luft- masses, M. Z., Bd. 23,, p. 241-244, 1906. phere, Geophys. Mag., Tokyo, v. 2, pp. 133- 138, 1930. MIEGHEM, J. Van, L'Eguation aux variations locales de la pression, Belgium, Institut JAUMOTTE, J., Le potentiel des vitesses dans Meteorologique, v. 24 I'atmosphere, Brussels, Acad. roy. de Bel- Royal Memoirs, 8, p., 1938. gique, 1932, 36, pp. J. van. Relation fondamentale JAUMOTTE, J., Sur la dynamique des fronts MIEGHEM, chauds. Com. beige de I'annee polaire 1932- entre les variations bariques et thermiques dans I'atmosphere, Acad. roy. de Belgique, 33, Memoires, Brussels, Ease. 1, pp. 9-32, 1932. CI. des Sci., Bull., Seance du 6 fev., 1937, no. 2, pp. 149-158. JAUMOTTE, J., Sur la variation du vent en F., Austausch und Wind, MZ, Bd. altitude, Acad, royal de Belgique, CI. des M6LLER, 48, pp. 69-80, 1931. Sci., 5e Serie, v. 22, no. 7, pp. 820-834, 1936. M6LLER, F., und P. Sieber, tJber die Abwei- chungen zwischen Wind und geostrophischen JEFFREYS, H., Cyclones and the general cir- Wind in der freien Atmosphdre, Ann. d. culation, Q. J. R. M. S., V. 53, Oct., pp. 401-406. 1927. Hydro., 1937, pp. 312-322. H., Energieumwandlung in einer JEFFREYS, H., The function of cyclones in MOLLWO, the general circulation. UGGI. Ass. Met., abgeschlossenen Luftmasse, Frankfurt, Wet- terdienststelle, Synoptische Bearbeitungen, Proc. Verb., Lisbon, 1933, II, 1935, pp. 219- 229. Linke Sonderheft, pp. 17-19, 1933. JEFFREYS, H., On fluid motions produced by MOLLWO, H., Zur Wirkungsweise der Rei- differences of temperature and humidity. bung in der freien Atmosphdre, Beitr. Phys. fr. At., Bd. 25-45, 1935. QJRMS, V. 51. Oct., 1925, pp. 347-356 22, pp. (diag. ). Also: The cause of cyclones, id., v. MIEGHEM, J. Van, Stir les variations dyna- 50, p. 61, 1924. miques de la pression atmospherique : Sur les champs de deformation dans les cyclones JEFFREYS. H.. On the dynamics of geostro- et les anticyclones, Belg., Acad. Roy., Bull, phic winds, OJRMS, v. 52, no. 217. pp. 85- de la CI. de Sci., 5th ser., t. 25, pp. 243-255, 103. 1926. (Crit. by WhinTile, p. 332; disc. 598-609, 1939. by Douglas, id, 1931, p. 423.) M6LLER, F., Druckfeld und Wind, M. Z., Bd. JEFFREYS, H., On the dynamics of wind, 284-292, 1936. QJRMS, V. 48, pp. 29-47, 1922. 53, pp. R. B., The present evidence KaRMaN, T. von. Turbulence and skin fric- MONTGOMERY, on the importance of lateral mixing pro- tion, Jn. Inst. Aeron. Sciences, v. 1, pp. 1-20, 1934. cesses in the ocean, B. A. M. S., v. 31, 3, pp. 87-94, 1930. KaRMaN, T. von and L. Howarth, On the zur Zyklogenese, statistical theory of isentropic turbulence, MiJGGE, R., Betrachtungen Z., Bd. 1-8, 1938. Proc. Roy. Soc, Lond. v. 164 A, p. 192, 1938. M. 55, pp. des Wetters, M. Z., Bd. KOBAYASHI, T., and others. Theoretical and MuGGE, R.. Energetik 168-176, 1935. experimental studies of convectional cir- 52, pp, culation and its relation to land and sea MiJGGE, R., uber das Wesen der Steuerung, breezes. Rep. Aero. Res. Inst., Tokyo, v. 12, M. Z., Bd. 55, pp. 197-205, 1938. no. 1, 1938, 67 pp. MuGGE, R., und P. Sieber, Tiber wetterwirk- KOTSCHIN._ N., uber die Beschleunigung der same Druckdnderungen, M. Z., Bd. 52, pp. discontinuitatsfldchen in der Atmosnhdre, 413-418, 1935. Beitr. Phys. fr. At., Bd. 19, pp. 7-16, 1932. NORMAND, C. W. B., Sources of energy of KOTSCHIN N., lifter die StabiHtat von Mar- storms. 25th Indian Sci. Congr., Calcutta gulesschen Diskontinuitdtsfldchen, Beitr. 1938. Proc. 19 pp. [See also his papers in Phys. fr. At., Bd. 18, pp. 129-164, 1935. QJRMS, 1937-8, on latent instability, etc.] LINKE, P., tjber die Entstehung von strato- OOMA, S., The fundamental equations of ino- sphdrischen Luftdruckwellen infnlge Ander- tion in anisotropic turbulent flow, J. Met. ung des Diffusionszus-andes der Atmosphdre, Soc, Japan, s. 2, v. 15, pp. 226-234, 1937. Beitr. z. Phys. d. fr. Atm., Bd. 13, pp. 123 PALMeN, E., liber die Gleichgewichtsbedin- ff., 1922. gungen beim dritten Sandstromschen Win- LUDLOFF, H., StabiHtat der Zyklonenwellen, tertyvus, Beit. Phys. fr. At., Bd. 16, H. 1, Ann. d. Physik, v. 8, pp. 615, ff., 1981. pp. 26-28, 1929. 186 AIR MASS ANALYSIS

PALMeN, E., ijber die Horizontalstromungen RICHARDSON, L. F., and others. The var- in der TJmgebung von beweglichen atmos- iance of upper wind and the accumulation of phdrischen Fronten, Mitt. Met. Inst. Univ. m,ass, Mem. Roy. Met. Soc, v. 1, no. 4, pp.

Helsingfors, no. 8, 1928, 21 pp. ; from Soc. 59-78, 1930. Scient. Fenn, Comm. Phys. Math., v. 4, ROSSBY, C.-G., Convection in the free atmos- 1928, no. 20. phere and over a heated surface, MWR, v. PALMeN, E., iJber die Natur der Luftdruck- 55, pp. 1-5, 1927. schwankungen in hoheren Schichten, Beitr. ROSSBY, C.-G., Dynamics of steady ocean Phys. fr. At., Bd. 14, pp. 147-153, 1928. currents in the light of experimental fluid PALMeN E., iJber die Temperaturverteilung mechanics. Papers in Physical Oceanog- in der Stratosphdre und ihren Einfluss auf raphy and Meteorology, Massachusetts Insti- die Dynamik des Welters, M. Z., Bd. 51, pp. tute of Technology and Woods Hole Ocean- 17-23, 1934. ographic Institution, Vol. V, No. 1, 1936. (Rev'd., Defant, Ann. d. Hyd., PARR, A. E., On the probable relationship 1937, pp. between the vertical stability and lateral 58-67.) mixing processes, J. du Conseil, Vol. XI, ROSSBY, C.-G., Note on shearing stresses No. 3, 1936. [Rev'd, BAMS, No. 6-7, 1937, caused by large scale lateral mixing, Proc p. 210, No. 9, p. 306]. 5th Cong. Applied Mech., 1938, pp. 379-382. PEKERIS, C. L., Wave-distribution in a ho- ROSSBY, C.-G., On temperature changes in mogeneous current. Trans. Amer. Geophys. the stratosphere resulting from shrinking Union, 1938, pt. 1, p. 163-164. and stretching, Beitr. z. Phys. d. fr. At., PHILLIPPS, H., Die Abweichung vom geos- Bd. 24, 1937, pp. 53-60. troplnschen Wind, M. Z., Bd. 56, pp. 460- ROSSBY, C.-G., On the mutual adjustment of 466, 1939. pressure and velocity distributions in cer- PHILLIFPS, H., Die Storungen des zonalen tain simple current systems, J. of Marine atmosphdrischen Gru7idzust.ande durch strat- Research, V. 1, no. 1, 1937-8, pp. 15-28. osphdrische Druckwellen, Wissenschaft. Ab- ROSSBY, C.-G., On the origin of travelling handl., Reichsamt f. Wetterdienst, Berlin, discontinuities in the atmosphere, Geog. Bd. 2, No. 3, 1936, 52 p. Ann., vol. 2, no. 2, 1924, pp. 180-189. PRANDTL, L., Beitrdge zur Mechanik der ROSSBY, C.-G., On the role of isentropic mix- Atmosphdre, Un Geod. et Geophys. Intern. ing in the general circulation of the at- 6ieme Ass. Gen., Edimbourgh, Sept., 1936, mosphere, Proc 5th Cong. Applied Mech., Proces verbaux de I'Ass. de Met., part 2, 1938, pp. 373-379. Mem. et Disc, pp. 171-202. ROSSBY, C.-G-, Solenoidal circulations re- PRANDTL, L., Meteorologische Anwendung sulting from lateral ^nixing. Trans. Amer. der Stromungslehre, Beitr. z. Phys. d. f. Geophys. Union, 1938, pt. 1, pp. 159-162. Atm., Bd. 19, pp. 188-202, 1932. ROSSBY, C.-G., Theory of atmospheric turbu- RAETHJEN, P., Advektive und konvektive, lence—a historical resume and outlook, stationdre und gegenldufige Druckdnderun- MWR, V. 55, 6-10, 1927. gen, M. Z., Bd. 56, pp. 133-142, 1939. ROSSBY, C.-G., Zustansdnderungen in at- RAETHJEN, P., Die Aufgleitfront, ihr Gleich- mosphdrischen Luftsdvlen, Beitr. z. Phys. d. gewicht und ihre Umlagerung, M. Z., Bd. fr. Atmos., Bd. 13, pp- 164-174, 1927. 51, h. 161-172, 1934. Further, id., v. 14, 1928, p. 65 flf. RAETHJEN, P., Die Bdenfront als fortschrei- ROSSBY, C -G., and Collaborators, Aerological tende Umlagerungswelle, M. Z., Bd. 51, pp. evidence of large scale mixing in the atmos- 9-17, 53-62, 1934. phere. Trans, of the Amer. Geophys. Union, Pt. I, 130-136. RAETHJEN, P., Das Gegenldufigkeitsgesetz 1937, pp. der Temperaturen in Stratosphdre und Tro- RYD, V. H., Travelling cyclones, Danske Met.

posphdre, M. Z., Bd. 52, pp. 418-424, 1935. Inst., Medd., no. 5, 1923, 124 pp. ; The energy the id., no. 1927, 96 RAETHJEN, P., Gleichgewichtstheorie der of winds, 7, pp. Zyklonen. M. Z., Bd. 53, pp. 401-408, 1936. SAKAKIBARA, S., Further investigations on the transverse eddy resistance acting on RAETHJEN, P., Hydrodynamische Betrach- in the lower atmosphere, Geo- tungen zur Mechanik der Eden, MZ, Bd. 47, moving air phys. Mag., Tokyo, v. 2, no. 139- pp. 431-437, 1930. 3, pp. 156, 1929. RAETHJEN, P., Konvektionstheorie der Auf- S., The general circulation of gleitfronten, MZ, Bd. 56, pp. 95-104, 1939. SAKURABA, the atmosphere in the light of the theory of RAETHJEN, P., Schrumpfung und Dehnung, turbulent motion (Grossaustausch) , Jn. Met. d. Hydr., Front und Frontalzone, Ann. 1938, Soc. Jap., V. 15, no. 8, 1937, p. (30). H. 8, pp. 383-388. SAKURABA, S., Maintenance of pressure an- RAETHJEN, P., Stabilitdtstheorie der Zyklo- omaly due to the horizontal stability of the nen. M. Z., Bd. 53, pp. 456-466, 1936. atmosphere, J. Met. Soc, Japan, v. 18, pp. RAETHJEN, P., Stationdre Strdmung unter 273-274, 1940. dem Einfluss der Schwere in stabil geschich- SAKURABA, S., On the maintenance of the teten FlUssigkeiten und Gasen, insbesondere subtropical anticyclones, Jn. Met. Soc. Jap., in der Atmosphdre, MZ, Bd. 48, pp. 288-306, V. 16, no. 7, 1938, p. (24). 1931. SAKURABA, S., Some quantitative studies on RAETHJEN, P., Theorie der Fronten und the general circulation of the atmosphere, Zyklonen. Ausblick und Ubersicht, M. Z., Jn. Met. Soc. Jap., v. 16, no. 1, 1938, p. (1). Bd. 50. pp. 450-454, 1933. SAKURABA, S., Turbulent friction in the at- RAETHJEN, P., Zur Thermo-Hydrodynamik mosphere, Geoph. Mag., Tokyo, v. 8, pp. Bden, Bd. 11-22, 1981. der MZ, 48, pp. 125-151. 1934; v. 9, pp. 11-21, 1935. REFSDAL, A., Zur Theorie der Zyklonen, M. SANDSTRoM, iJber das Entstehen und Ver- Z., Bd. 47, pp. 294-305, 1930. schwinden der Diskontinuitdten in der At- Z., Bd. 40, 37-39, 1923. RICHARDSON. L. F., and R. E. Munday, The mosphdre. M. pp. single-layer problem in the atmosphere and SANDSTROM. J. W., iJber die Temperaturver- the height-integral of pressure, Roy. Met. teilung in den allerhochsten Luftschichtung, Soc, Memoirs, v. 1, no. 2, pp. 17-34, 1926. Arkiv f. Math. Astr. och Fysik, v. 3, 1907. —

BIBLIOGRAPHY 187

SANDSTROM, J. W., On the relation between rotierenden Erde, I. Astrophysica Norvegica, atmospheric pressure and wind, Bull. Mt. V. 1, no. 7, pp. 237-340, Feb., 1936. Wea. Obsy., v. 3, 1911, p. 275-303 ; On mo- SOLBERG, H, Das zyklonen Problem, Intern. tions fluids, Ann. d. Hyd., June 1909, of Kong. f. techn. Mechanik, Stockholm, Verb. with disc, Dietzius, Beitr. Phys. fr. At- by 3, 1930. mos., V. 8, 1918, p. 29-52. Wenger, MZ, 1920, SPILHAUS, A. F., Note on the flow streams p. 241, Ann. d. Hyd., 1920, p. 112. of in a rotating system, J. of Marine Res., Vol. J. W., Untersuchungen iiber SANDSTR6M, 1, no. 1, pp. 29-33, 1939. die Polarfront, M. Z., Bd. 40, pp. 262-264, STuVE, G., Der Mechanismus der atmos- 1923 ; Bd. 41, pp. 33-36, 1924. phdrischen Steuerung, Frankfurt, Wetter- SANDSTR6M, J. W., fiber die Beziehung zwis- dienststelle, Synoptische Bearbeitungen, chen Temperatur und Luftbewegung in der Linke Sonderheft, pp. 8-17, 1933. Atmosphdre unter stationaren Verhdltnissen, STARR, V. P., The readjustment of certain MZ, 1902, pp. 161-170 ; further : ofversigt af unstable atmospheric systems under coti- Kongl. Vetenskaps-Akad. Forhandl ; v. 58, servation of vorticity, MWR., v. 67, pp. 1901 (Stockholm), pp. 759-774, v. 59, 1902, 125-133, 1939. (cont. ) ; a.nd Anwendung von Prof. Bjerknes' Theorie, Svensk Vet. Akad. Handl., v. 33, STiJVE, G., und R. Miigge, Energetik des 1902. Wetters, Beitr. z. Phys. d. fr. Atm., Bd. 22, pp. 206-248, 1935 SANDSTR6M, J. W., Meteorologische Studien ini Schwedischen Hochgebirge, Kgl. Veten- SUTCLIFFE, R. C, Cyclonic and Anticyclonic skaps- och Vitterhets-Samhalles, Handlingar, Development, QJRMS, v. 64, 1938, p. 500 ff, 4th Ser., 17, 1916, 48 p. Also see Bull. Mt. v. 65, 1939, pp. 518-24 ; crit., id., 1939, p. 77. Wea. Obsy., v. 5, 1912, p. 83-113. Crit. by 236. Disc, id., v. 66, 1940, p. V. Bjerknes, Uber Thermodynamischen Mas- SUTTON, O. G., Wind structure and evapora- chinen ... .Abhand. Math. Phys. Kl. tion in a turbtdent atynosphere, Proc of the sachs. Gesell. d. Wiss., Leipzig, 1916. Crit. Roy. Soc London, Ser. A., v. 146, pp. 701 by Wenger, Phys. Zeit., 1916, p. 547. ff., 1934. (Cf. check by Lettau, Ann. der 155-60.) SCHERHAG, R., Warum okkludieren die Zyk- Hyd., v. 56, pp. lonen?, Ann. der Hydrogr., May, 1938, pp. SUZUKI, S., and H. Oomori, On atmospheric 229-237. Waves, Gerland's Beitr. Geophys., v. 49, pp. 301-318, 1937. SCHMIDT, W., Atmospheric waves of short period, QJRMS, v. 37, 1911, p. 73-9. SVERDRUP, H. U., Austausch und Stabilitat in der untersten Luftschicht, MZ, 10-15, SCHMAUSS, A., Ursache und Wirkung in der 1936. See further: QJRMS, v. 62, p. 124, p. Meteorologie, M. Z., Bd. 38, pp. 8-11, 1921. 461, v. 63, p. 105 ; v. 65, p. 57 ; Geofys. SCHMIDT, W., Schrumpfen und Strecken in Publ., V. 11, no. 7 ; Jn. Mar. Res., v. 1, p. der freisn Atmosphdre, Beitr. z. Phys. d. fr. 3-14; Ann. d Hyd., v. 64, 1936, p. 41-7. At., Bd. 7, pp. 103-149, 1916. H. U., On the influence of stab- SCHWABL, W., Experimentelle Untersuchun- SVERDRUP, ility and instability on the wind profile and gen zur allgemeinen Zirkulation der Atmos- the eddy conductivity near the ground, Proc. phdre, MZ, Bd. pp. 208-212, 1933. 50, of the Fifth International Congr. for Ap- SEKERA, Z., Zur Wellengewegung in FlUssig- plied Mechanics, J. Wiley and Sons, N. Y., keitsschiehten mit vertikal verdnderlicher pp. 369-372. 1938. Geschwindigkeit, Astrophysica Norvegica, v. SVERDRUP, H. U. and J. Holtsmark, iJber 3, no. 1, pp. 1-69, Jan., 1938. die Beziehung swischen Beschleunigungen SHAW, Napier, The birth and death of cy- und Gradientendnderungen und ihre prog- clones, London. Met. Office, Geophys. Mem- nostische Verwendung, Leipzig, Univ., Geoph. oirs,, no. 19, pp. 213-227, 1922. Inst., Veroff, Bd. 2, H. 3, pp. 143-172, 1917. SHOULEJKIN, W., The physical picture of SVERDRUP, H. U., und J. Holtsmark, iJber the heat currents going from the sea to the die Reibung an der Erdoberfldche und die continent (principles of the monsoon theory). direkte Vorausberechnung des Windes mit Bull. Acad. Sci. URSS, CI. Sci. Math. Nat., Hilfe der hydrodynamischen Bewegungs- Ser. Geogr-Geophys., vol. 1937, no. 3, p. gleichungen, Leipzig, Univ., Geophys. Inst., 305-6. Further, by Goussev, id., vol. 1938, Veroffe, 2. Serie, Bd. 2, Heft 2, pp. 97- no. 4, p. 344. 141, 1917. P., SIEBER, ijber den Einfluss von Druckdn- TAYLOR, G- I., Statistical theory of turbu- derungen auf das Wetter, Beitr. Phys. fr. lence: Part 4 Diffusion in a turbulent air At., Bd. 23, H. 4, pp. 249-274, 1936. stream, Roy. Soc. Lond., Proc, A, v. 151, SOLBERG, H., Integrationen der atmosphd- pp. 421-478, Sept., 1935. (See also Jn. Aero. — V. no. 311-15.) rischen stiirungsgleichungen : I Wellenbe- Sci., 4, 8, pp. wegungen in rotierenden inkompressiblen TOLLMIEN, W., Berechnung turbvlenter Aus- Fliissigkeitsschichten, Geofys. Pub., v. 5, no. breitungs-vorgange, Zeit. f. angew. Math, 9, pp. 3-120, 1928. u. Phys. V. 6, 1926, p. 468. SOLBERG, H., Le mouvement d'inertie de TRABERT, W., Der Zusammenhang zwischen I'atmosphere stable et son role dans la the- Luftdruck- und Temperaturverhaeltnissen, orie des cyclones, Un. Geod. et Geophys. MZ, 1910, pp. 301-307. Intern.. 6ieme Ass. Gen., Edinbourgh, Sept., A., iJber die vertikale Machtigheit 1936, Proces verbaux de I'Ass. de Met., part WAGNER, einer thermischen Zirkulations und die 2, Mem. et Disc, pp. 67-82. vertikale Temperaturschichtung in dersel- SOLBERG, H., Schwingungen und Wellenbe- ben, Gerl. Beitr. Geophys. Bd. 51, pp. 410- wegungen in einer Atmosphdre mit nach 421, 1937. oben abnehmender Temperatur, Astrophysica WALKER, G. T., The dynamics of cyclone Norvegica, Vol. 2, no. 2, pp. 124-172, 1936. formation. Beitr. Phys. d. Fr. Atmos., Bd. SOLBERG, H., Sur le frottement dans les cou- 15, 1929, pp. 83-86. ches basses de I'atmosphere. Forhandl. 17de WALKER, G. T., Note on Bjerknes's contribu- Skand. Naturforskarmote, Goteborg, 1923 tion of 1921 to the mechanics of the general SOLBERG, H., uber die freien Schwingungen circulations, QJRMS, v. 51, p. 337-345, 1925, einer homogenen FlUssigkeitsschicht auf der Corr., v. 54, p. 26, 1928. 188 AIR MASS ANALYSIS

WATANABE, S., The equation of motion of (Comments by Sakuraba, J. Met. Soc, Jap., a viscous fluid accoTnpanied by "micro- 1938, p. 381 (33).) gyrostatic field", Geophys. Mag., Tokyo, v. 5, pp. 173-181, 1932. WuNSCHE, W., tsber die Existenz langsamer Luftdruckschwingungen auf der rotierenden WENK, F., Anderung der Stabilitdt atmos- Erde, Veroff. Geophys. Inst. Univ. vhdrischer Schichtungen bei adiabatischer Leipzig. Bd. 11, No. 3, pp. 157-199, 1938. Hebung, Beitr. Phys. fr. At.. Bd. 16. H. 4. pp. 298-304, 1929. WHIPPLE, F. J. W., The laws of approach WEXLER, H., Formation of polar anticy- to the geostrophic wind. QJRMS. v. 46, pp. cyclones, M. W. R.. v. 7. pp. 229-236, 1937. 39-53. 1920. THE STATISTICAL AND SCHEMATIC BACKGROUND FOR SYNOPTIC PRACTICE:

1. Mean (General) Circulation

a. Surface Data

ALLEN, R. A., Statistical studies of certain DEFANT, A.. Die Zirkulation der Atmosphdre characteristics of the general circulation of in den gemassigten Breiten, Geog. Ann. v. the northern hemisphere, QJRMS, v. 66, 3. p. 209 ff., 1921. Supplement, pp. 88-101, 1940. DEPPERMANN. C. F., The mean transport ARAKAWA, H., The formation of hurricanes of air in the Indian and South Pacific in the South Pacific and the outbreaks of Oceans, U. S. Weather Bureau, Manila Cen- cold air from the North Polar region, J. tral Obs., 1935, 13 p. 1-6 Met. Soc, Japan, v. 18, pp. [Abstr. in DEPPERMANN, C. E., Outlines of Philip- Eng. p. (1)], 1940. pines frontology. Weather Bur.. Manila. ASKNAZY, A. L, Of the subject of the sum- 1936, 27 pp. circulation mer air on the European terri- DURST, C. S.. The doldrums of the Atlantic, tory of the USSR. J. Geophys., v. 4, no. 4, London. Met. Office, Geophys. Memoirs, (v. 439-448, 1934. (Also later in pp. papers 3,) no. 28, pp. 229-238. 1926. Met. i. Hyd., 1936-38.) EREDIA, F., La meteorologia e I'aerologia. BARKOW, E., Die Ergebnisse der meteoro- degli oceani: (1) L'Oceano Atlantico Sud. logischen Beobachtungen der Deutschen An- Suppl. al fasc. d. "Revista Maritima", Apr. tarktischen Expedition, 1911-1912. Berlin, 1932, 176 p., (2) L'Oceano Atlantico Nord, Preuss. Met. Inst., Abhandlungen, Bd. 7, nr. Ministero della Marina (Italy), 1935, 300 p. 1-166. 6, pp. [Valuable summaries of lit., includ. upper- BAUER, G., Luftzirkulation und Niederschlag- air data.] sverhaltnisse in Vorderasien, Gerl. Beitr. EVJEN, Sigurd, vber statistische Unter- Geophys., Bd. 45, pp. 381-548, 1935. suchungen von "Zyklonentdtigkeit" mittels BERGERON, T., Richtlinien einer dynamis- Isobarenkarten, MZ, Bd. 49, pp. 180-186. chen Klimatologie, M. Z., Bd. 47, pp. 246- 1932. 262, 1930. EXNER, F. M., iJber die Zirkulationen kalter BJERKNES, v.. The meteorology of the tem- und warmer Luft zwischen hohen und niedri- perate zone and the general atmospheric gen Breiten. Vienna, Akad. Wiss., Sitzb.,

circulation, M. W. R., Jan., 1921. pp. 1-3 ; Bd. 137, Ila, pp. 189-225, 1928. Nature, June 24, 1920, pp. 522-523. (Com- EXNER, F. M., The weather situation in ments by von Ficker, Beitr. Phys. fr. Atmos., Europe in the winter of 1928-29, M. W. R.. V. 9, 1920, p. 130-1356.) V. 57. pp. 498-499, [Translated by W. W. BJERKNES, v., Polar front meteorology Reed from M. Z., April 1929.] (Abstr.). QJRMS. v. 51, 1925, pp. 261-268. FERRAZ, J. de S., Hurricanes and South At- BRITISH Nat. Com. for Polar Year, British lantic circulation, BAMS, v. 20, no. 8, pp. Polar Year Expedition, Fort Rae, N. W. 334-335, 1939. Canada, 1932-33, London, (2 vols.) 1937. FITTON, E. M.. The climates of Alaska, M. BROOKS, C. E. P., Studies on the mean at- W. R., V. 58, pp. 85-103, 1930. mospheric circulation, BAMS, v. 18, pp. 31.?- FORSCHUNGSINSTITUT fur Langfristige 322. 1937. Witterungsvorhersage des Reichswetterdien- BROOKS, C. E. P., and H. W. Braby, The stes. Bad Homburg v. d. Hohe, Mitteleuro- clash of the trades in the Pacific, QJRMS, paischer Witterungsbericht, (Publ. monthly

V. 47, pp. 1-14, Jan., 1921. sinse 1930 ; various maps of the northern hemisphere, pressure distribution at BROOKS, C. E. P., The warming Arctic, Met. mean various levels, depart, of pressure 60- Mag., V. 73, pp. 29-32, 1938. from year average, pressure change, etc.) BROWN, R., The Soviet Polar enterprise, some FROST, R. L., A climatological review of the preliminary results. Nature, March 12, 1938, Alaska-Yukon plateau, M. W. R., v. 62, pp. p. 480, BAMS, Nov. 1938, 411. p. 269-280, 1934. H., DALLDORF, Troposphdrischer Meridional- FUJIWHARA. S. and N. Yamamoto. Compari- austausch in den gemassigten Breiten, Aus son of the general circulation in the Far d. Arch. d. Deutsch. Seewarte, Bd. 57, Nr. East and Europe, Jn. Met. Soc. Jap., v. 17, 10, 1937, 21 pp. no. 9, p. (35). DEFANT, A., Die Austauschgrosse der atmos- HAURWITZ, B., Investigations of atmosphdrischen und ozeanischen Zirknlation, pheric periodicities at the Geophysical Insti- Ann. d. Hydrog., Bd. 54, pp. 12 ff., 1926. tute, Leipzig, Germany, M. W. R., v. 61, DEFANT, A., Die Schwankungen der atmos- pp. 219-221, 1933. phdrischen Zirkulation iiber dem Nordatlan- HENRY, A. J., Professor Exner on the circv^ tischen Ozean im, -25-jdhrigen Zeitraum, lation of cold and warm, air between high lSSl-1905, Geog. Ann., Bd. 6, H. 4, 1924, and low latitudes, M. W. R., v. 57, pp. 491- pp. 13-41. 498, 1929. )

BIBLIOGRAPHY 189

HESSELBERG, Th., Arbeitsmethoden einer LOEWE,, F., The Greenland ice cap as seen by a dynamischen Klimatologie, Beitr. z. Phys. meteorologist, QJRMS, v. 62, no. 266, pp. 359- d. fr. Atm., Bd. 19, pp. 291-305, 1932. 378, 1936. HILDEBRANDSSON, H. H., et L. T. de Bort, LU, A., The monthly pressure distribution and Les bases de la meteorologie dynamique, his- the surface winds in the Far East, China, torique, etat de nos connaissances, Paris, Nat. Res. Inst. Met., Memoir, v. 12, no. 4, Gauthier-Vniars, 1907, 2 vols. 25 pp., 1939. HILLEBRAND, R., Untersuchungen iiber den LYR, E., The empirical studies of the at- atmosphdrischen Grossaustausch und seine mospheric circulation. Met. i Hydrol., v. bedeutung als Klimafaktor, Veroff. Geophys. 1937, no. 2, pp. 26-33. Inst. Univ. Leipzig, Bd. 11, pp. 311-392, MARKUS, E., Der Nordatlantik als Vertie- 1939. (bibliogr.) fungsgebiet barometrischer Minima, Ann. d. HOWARD, A. G., South African meteorology: Hydr., 1934, H. 6, pp. 225-232. Types of atmospheric pressure, their dura- MEINARDUS, W., Deutsche Siidpolar-Expedi- tion and movements. So. African Jn. of Sci., tion 1901-1903, Berlin, 1923, 578 p. Bd. Ill, "- 16, pp. 273-284, 1920. Meteorologie, I. 1. Teil 1. Meteorologische JENSEN, AD. S., Concerning a change of Ergebnisse der Winterstation des "Gauss" climate during recent decades in the arctic 1902-1903, I. 1. Teil 2. Meteorologische Er- and subarctic regions, from Greenland in the gebnisse der Kerguelen-Station 1902-1903, I. west to Eurasia in the east, and contempo- 1. Teil 3. Meteorologische Ergebnisse der rary biological and geophysical changes, K. Seefahrt des "Gauss" 1901-1903. Danske Videns. Se'skab., Biol. Medd., v. MERRIAM, W. B., Some observations on the 14. 8. 75 pp. 1939. (Best review of subject; climate and the "Northeaster" storms of the bibliog. Kodiak Archivelago. Alaska, BAMS, v. 17, KIDSON, E., British Antarctic Expedition. pp. 351-354, Dec, 1936. 1907-09: Reports on the scientific investiga- MIDDLETON, W. E. K., The climate of the tions, meteorology, Melbourne, n. d., 188 pp. Gulf of St. Lawrence and surrounding re- KIDSON, E., The circulation of the atmosphere gions in Canada and Newfoundland, as it in the Australia-New Zealand Region, Proc. affects aviation, Canada, Met. Serv., Met. 5th Pacific Sci. Cong., v. 3, pp. 661-666. Memoirs, v. 1., no. 1, pp. 1-40, 1935. KIDSON, E., The general circulation on a MILLER, E. C, Relative frequency of centers water hemisphere QJRMS, v. 59, no. 252, of cyclones and anticyclones in the United pp. 372-373, 1933. States, M. W. R., v. 60, pp. 6-11,1932. KIDSON, E., Notes on the general circulation MIRRLEES, S. T. A., Meteorological results in the New Zealand region, Gerl. Beitr. Geo- of the British Arctic air-route expedition phys., Bd. 34, pp. 1-8, 1931. 1930-31, London, Met. Office, Geophys. Me- no. 61 (v. 3-30, 1934. KIDSON, E., Problems of antarctic meteor- moirs, 7), pp. ology, QJRMS, V. 58, pp. 219-226, 1932. MITCHELL, C. L., Cyclones and anticyclones KON. NEDERLANDSCH MET. INST., Ocean- of the northern hemisphere, January to ographische en Meteorologische Waarnemin- April, inclusive, 1925, M. W. R., v. 58, pp. gen in den Atlantischen Oceaan. Atlas of 1-22, 1930. monthly mean charts, in parts, 1926-35. MITCHELL, C. L., West Indian hurricanes cyclones the North KoPPEN, W., and R. Geiger, Handbuch der and other tropical of M. R., Suppl. no. 24, Klimatologie, Berlin, Gebriider Borntraeger, Atlantic ocean, W. 1924. 47 pp. 1930— . See the following parts in parti- beiden Haupt- cular : Teil G, Klimakunde von SUdamerika, MOESE O., and G. Schinze. Die frontalzonen und PF—Bemerkung uber by K. Knoch ; Teil H, Klimakunde von Mit- AF Hydrogr., telamerika. by K. Sapper ; Teil I, Climat- ihre Rolle fur Europa, Ann. der ology of the West Indies by R. DeC. Ward Oct. 1932, pp. 408-14. and C. F. Brooks; Teil J, Part 1, The NAVARRETE, J. B., The cold pole of South climates of North America, by R. DeC. Am.erica, M. W. R., v. 61, p. 302, 1933. Ward, C. F. Brooks, and A. J. Connor ; Teil PETZOW, Georg, Herkunft, Haufigkeit und J, Part 2. The climates of North America II, Schicksal der von 1S89 bis 1912 iiber dem Canada, by A. J. Connor ; Teil K. Part I, Schwarzen Meer beobachteten Zyklonen, Ber- ijbersicht iiber das Klima dcs Polarmeeres lin, E. Eberinsr, 1931. (Diss. Berlin Univ.) und des Kanadischen Archipels, by H. U. S.. Meteorologie de Madagascar. Sverdrup ; Teil K, Part 2, Dos Klima der POISSON, C. Phys. Nat. et Polit. de Mad., Kiisten von Gronland. by H. Petersen ; Teil K, V. 3 of Hist. Part 3, Das Klima des Gronlnndischen inlan- ed. by Grandidier, Paris, 1930. deises. by F. Loewe ; Teil L. Klima von Nord- RICHARDSON, R. W., Winter air-mass con- westeurova und den Inseln von Island bis vergence over the North Pacific, M. W. R., Franz-Josef-Land, by B. J. Birkeland ; Teil S, V. 64, June, 1936, pp. 199-202. Part 1, Climatoloay of Australia, by G. Tay- RODEWALD, M., Das Griine Kap Westafri- lor ; Teil S. Part 2, CHmafnloay of New Zea- kas .als Stdtte einer guasistationdren Stro- land, by E. Kidson ; Teil T. KHmakunde der mungssingularitdt, Ann. d. Hydr., 1937, H. Siidsee Inseln. bv G. Schott ; Teil U. Klima- 206-211. kunde der Antarktis. by W. Meinardus. 5, pp. RODEWALD, M., Eine sekunddre subtropisehe KULLMER, C. J., The latitude shift of the Zyklonenbildungsstdtte im mittleren Nord storm traxk in the 11-vear solar period. Atlantik, Ann. d. Hydrog., Bd. 64, H. 10, Storm frequency mar)s the United States. of 1936. pp. 433-476. 1SH3-1930. Washington, Sm'"th. Inst. Misc. C.-G.. Relation between variations Coll., v. 98, no. 2, 34 pp., 1933. ROSSBY, in the intensity of the zonal circulation of LEA, C. A., A Preliminary analysis of pres- the atmosphere and the displacements of sure observations in MaJn.ua, Malayan Met'l. the semi-permanent centers of action. J. of Serv., Memoirs, No. 1, 1932, 8 pp. Marine Research, v. 2, no. 1, pp. 38-55, 1939. LIR, E., Prinzipien der Klnssifikation synop- SANDSTRoM. J. W., Monatliche, jdhrliche, tischer Prnzpsses. J. of Geonhys., v. 1, no. und zehnjdhrige Luftversetzungen in Eu- 1-2, pp. 146-165, 1931. (Also many later rope, 1901-1910, Kel. Vetenskaps och Vit-

papers in id., and in Met. i Hyd., 1936-39 ; terhets-Samhalles, Handlingar, 4th Ser., 19, see Lyr, infra. ) 1916, 64, pp. — —

190 AIR MASS ANALYSIS

SAWYER, L. Doris, Some regions of forma- SVERDRUP, H. v.. The North Polar cover of tion of depressions in the North Atlantic, cold air, M. W. R., v. 54, pp. 471-475, 1926. London. Met. Office, Prof. Notes, no. 50 (v. TAYLOR, G., Australian Meteorology, Oxford, 2-7, 1928. 4), pp. 1920, 305 pp. SCHERHAG, R., Die Erwdrmung des Polar- THORNTHWAITE, C. W., et al.. Climatic re- gebiets, Ann. d. Hydr., 57-66. 1939, H. 2, pp. search in the Soil Conservation Service, SCHERHAG, R., Die Zunahme der atmos- M. W. R., V. 66, pp. 351-368, 1938. pharischen Zirkulation in den letzten 25 TU, C.-W., A preliminary study on the mean Jahren, Ann. d. Hydr., 1936, H. 397- 9, pp. air currents and fronts of China, China, 406. Nat. Res. Inst. Met., Memoir, v. 11, no. 3, SCHMAUSS, A., Synoptische Singnlaritdten, 12 pp., 1937. MZ, Bd. 55, pp. 385-403, 1938. U. S. WEATHER bureau. Atlas of climatic SCHNEIDER, L. R., Meteorological investiga- charts of the oceans, Washington, 1938. tions in Greenland during 1930-31, M. W. WAGNER, A., Zur Bestimmung der Intensitdt R., V. 58, p. 412, 1930. der allgemeinen Zirkulation, Ann. d. Hydro., SCHOTT, G., Geographie des Atlantischen 1938, pp. 161-172. Ozeans, Hamburg, 1926, xiv, 368 p. WEICKMANN, L., P. Zistler, et al., Zum SCHOTT, G., Geographie des Indischen und Klima der Turkei, Leipzig, Geophys. Inst. sullen Ozeans, Hamburg, 1935, 413 pp. Univ., 1922-28. [In 4 parts ; pt. 4, by

SEILKOPF, H., GrundzUge der Flugmeteoro- Koschmeider, on upper vyinds. ] logie des Luftwegs noch Ostasien, Archiv d. WERENSKIOLD, W., Mean monthly air Deutschen Seewarte, v. 44, no. 3, 1927. transport over the North Pacific Ocean, SHAW, N., The polar front, QJRMS, v. 58, Kristiania, Geofys. Komm., Geofys. Pub., v. Oct., 1932, pp. 482-484. 2, no. 9, pp. 3-55, 1922. SINJAGIN, A. A., An essay on circulation in WEXLER, H., and J. Namias, Mean monthly middle latitudes, (In Russian with English isentroinc charts and their relation to de- summary), U. S. S. R., Central direction of partures of summer rainfall. Trans. Amer. the hydro-meteorological service. Central Geophys. Union, 1938, pt. 1, pp. 164-170. geophys. Obsy., Transactions, Edition 4, pp. 107-154, Leningrad, 1935. WHERLb, p., and P. Schereschewsky, Sur le front polaire Austral, Pet. Mitt., Erg. Heft, SIMPSON, G. C, British Antarctic Expedi- 191, 1927, pp. 77-84. tion 1910-1913: Calcutta, 1919, v. 1 Discus- sion ; V. 2 Weather Maps. WILLETT, H. C, The importance of observa- STREMOUSSOV, N. V., About the synoptic tions from the upper atmosphere in long- processes in the eastern part of the Asiatic range weather forecasting, BAMS, v. 18, pp. continent and the adjacent seas (abstract), 284-7, 1937. BAMS, V. 17, p. 310, 1936. WILLETT, H. C, Results obtained from the SUTCLIFFE, R. C, Barometer fluctuations at analysis of northern-hemisphere weather Malta, London, Met. Office, Prof. Notes, no. maps for 1936-37, Trans. Amer. Geophys. 62 (v. 5), pp. 3-10, 1931. Un., 1937, Pt. I, pp. 146-8.

b. Aerological Data

ANDRUS, C. G., Ceiling and visibility in the BEALS, E. A., The Northeast Trade Winds of United States, Northeastern states, M. W. the North Pacific, M. W. R., v. 55, pp. 211- R., v 58, pp. 198-199, 1930. 221, 1927. [ANON], The height of stratosphere over the BECKER, R. B., Dos Flugklima Gronlands lower Yangtze Valley, (abstract in Eng. ), (Beitrage zur Meteorologie des Luftweges Met. Mag. (China), v. 12, no. 8, p. 456, iiber Gronland, I), Aus dem Archiv der Aug., 1936. deutschen Seewarte, Hamburg, Bd. 52, nr. ATMANATHAN, S., On the relation between 4, 32 pp., 1933. the weather and the variation of the normal BEMMELEN, W. V., The Antitrades, MWR, vertical gradient of temperature in N. W. V. 50, 1922, pp. 90-91. India, India Met. Dept., Scientific Notes, v. BEMMELEN, W. van, Der intertropische Teil 4, no. 32, pp. 7-17, 1931. der allgemeinen Zirkulation nach Beoback- BALLARD, J. C, The diurnal variation of tungen in Batavia, M. Z., Bd. 41, pp. 133- free-air temperature and of the temperature 141, 1924. Abstr. MWR, Sept. 1924, pp. lapse rate, M. W. R., v. 61, pp. 61-80, 1933. 441-6. BALLARD, J. C, Some results of sounding- BERMUDA Meteorological Office, Summary of

balloon observations during the Second In- Observations, (surface and upper air) . Ann. ternational Polar Year, Aug., 1932 to Aug., 1936-. 1933, inclusive, M. W. R., v. 62, 45-53, pp. F. H., Results nephoscope ob- 1934. BIGELOW, of servations in the West Indies, M. W. R., v. BANERJI, S. K., The effect of Indian moun- 32, 1904, pp. tain ranges on air motion, Indian J. Phys., M., Genesi e sviluppo del mon- V. 5, pt. 7, 1930. BOSSOLASCO, sone di SW sull'Oceano Indiana, Geofis. Pura BARLOW, E. W., The air circtdation upper of e Applicata, v. 1, fasc. 1, 1939, pp. 35-44. the Atlantic Ocean, London, Met. Office, Prof. Notes, no. 39 (v. 3), pp. 200-217, BOSSOLASCO, M., Das Stromungssyotem der 1925. Luft Uber Magadisciu [Somaliland] . Zoit. Geophys. v. 10, pp. 360-369, 1934. BAUR, F. und H. Philipps, Der Warmehaushalt der Lufthidle der Nordhalbkugel im Jan, und BRAAK. C, Drachen- Freiballon- und Fessel- Juli. Part 1, Gerlands Beitrage z. Geophys., ballonbeobachtungen [Java], Batavia, K. Bd. 42, pp. 160-207, 1934: Part 2, ibid. Bd. Magnetisch en Meteorologisch Obs., Verhan- 45, pp. 82-132. delingen. No. 3, 1915, 58 p. BEALS, E. A., Free-air winds over Honolulu BROOKS. C. E. P., Recent studies on the and Guam, M. W. R., v. 55, pp. 222-226, mean atmospheric circulation. Met. Mag., 1927. June and September, 1936, pp. 105-110, 177- ) ,

BIBLIOGRAPHY 191

18a. Reprinted, BAMS, v. 18, pp. 313-321, DEPPERMANN, C. E., The. upper air at 1937. Manila, Manila Obsy., Publ., Vol. 2, no. 5, BROOKS, C. E. P., and S. T. A. Mirrlees, A 1934. study of the atmospheric circtdation over DEUTSCHE Atlantische Expedition "Meteor" tropical London, Africa, Met. Office, Geo- 1925-1927, Wissenschaftliche Ergebnisse der phys. Memoirs, no. 55 (v. 6), pp. 5-15, 1932. deutschen atlantischen Expedition auf dem BROOKS, C. E. P., The climate of Ascension Forschungs- und Vermessungsschiff "Meteor" island, QJRMS. v. 57, 1931. Also: Geophys. 1927-1927. Hrsg. von A. Defant, Bd. 15. Mem. no. 33, Met. off. London, 1926. Die aerologischen Methoden und das aerolo- CAMM, H. E., and Baufield, Frequency and gische Beobachtungs-material. Von E. Kuhl- Velocity of wind at Sydney from Pilot bal- brodt und J. Reger. Berlin und Leipzig, loon obs. 1926-32. Sydney, 1934. W. de Gruyter, 1933. 305 pp. CANNEGIETER, H. G., Aerologische Beo- DEUTSCHE SEEWARTE, Luftfahrtblatt der bachiungen — in Reykjavik wahrend des Monatskarte fur den SUdatlantischen Ozean, Int. Polarjahres 1932-33, Kon. Nederlandsch Blatt 14, Mittlere Luftdruckver-teilung und Met. Inst., Ergeb. Aerol. Beob. no. 21A, Windverhdltnisse im Monat August, SiXd- 35 pp. The Hasue, 1933. (Of. for mean val- Winter, Hohenwinde in den Monaten Mai- ues, Bleeker, Beitr. Phys. Fr. Atmos., v. Sept. (Folded chart, Hamburg, 1928.) 24, p. 117-22, V. 23, p. 39-44). DINES, L. H. G., Mean values the relative CARMICHAEL, H. and Dymond, E. G., Upper of air investigations in northwest Greenland, humidity at different heights in the atmosphere over England, QJRMS, v. 59, pp. 157- Roy. Soc., Lond., Proe., A, v. 171, pp. 345- 1933. 359, June 1939. 162, CAVE, C, Structure of the atmosphere in DOHRMANN, Heinz, Untersuchung iiber die clear weather. Cambridge, 1912, 144 p. Ursachen der Hebung und Auflosung der Passatinversion im Begiet der dquatorialert CHAPEL, L. T., The significance of air move- Calmen, Dissertation, ments across the Equator in relation to the Fr.-Wilhelms-Univ. Berlin, 1937, 42 development and early movement of tropical pp. cyclones, M. W. R., v. 62, pp. 433-437, Dec, DOUGLAS, C. K. M., Further researches into 1934. the European upper air data, QJRMS, V. CHATTERJEE, G., and N. K. Sur, Discussion 50, pp. 339-363, 1924. (Cont. from id., v. of results of soundings of temperature and 47, pp. 23-43, 1921.) humidity at Jhikargacha (Bengal) in April and May 1929, India Meteorological Dept., DURWARD, J., Upper winds at Nicosia, Cy- prus, Met. Off. London, Prof. Notes, no. 87, Memoirs, v. 26, Pt. 9, pp. 165-187, 1938. 18 pp. 1938. CHIPLONKAR, M. W., The Distribution of temperature in the lower stratosphere, In- DURWARD, J., Upper winds measured at dian Academy of Sciences, Proc. v. 11, No. M/Y Imperia, Mirabella Bay, Crete, Met. 1, Sec. A., pp. 39-52, 1940. Off. Lond., Prof. Notes, no. 79, 1937, 13 pp. CHIPLONKAR, M. W., Further statistical EDLUND, O., Meteorologische und aerolo- studies of temperature and pressure in the gische Beobachtungen der Norwegischen upper atmosphere over India, Beitr. Phys. Nowaja Semlia Expedition im, Sommer 1921, fr. At., Bd. 23, 238-247, 1936. H. 3, pp. Report of Scientific Results of the Norwe- CHU, C, Circulation of atmosphere over gian Expedition to Novsraja Semlja 1921, China, China, Nat. Res. Inst. Met., Memoir, Oslo, 1928, 39 pp. no. 4, 55 pp., 1934. EKHART, E., Zum Klima der freien Atmos- CHU, W. Y., The upper air current observa- phdre iiber U. S. A. (2 parts), Beitrage z. tions in Nanking, China, Nat. Res. Inst. Phys. fr. At., Bd. 26, Heft 1 and 2, 1939, Met., Memoir, No. 9, pp. 25-41, 1937. pp. 50-66, 77-107. CLAPP, P. F., Mean monthly isentropic charts, EREDIA, F., Le corrienti aeree al suolo e a BAMS, V. 19, pp. 1938 [abstract.] (Such quote a Tripoli, La Met. Prat., Ann. 17, no. charts are pubd. in back of MWR each aeree al suolo 6, 1936, 255-65 ; Le corriente month, 1940-. e a quote a Bengasi, id., no. 1, pp. 4-15. CLAYTON, H. H., The diurnal and annual EREDIA, Ph., Le Osservazioni Aerologiche al periods of temperature, humidity and wind Capo Guardafui, Beitr. Phys. fr. At., Bd. velocity up to i km. in the free air and the 21, pp. 193-207, 1934. average vertical gradient of these elements F. L'esplorazione dell' atmosfera a at Blue HiU, Annals of the Astron. Obs. of EREDIA, mezzo di palloni piloti a bordo di novi mer- Harvard College, v. 58, pt. 1, 1904, 62 p. cantili, Annali dell-Ufficio Presagi, vol. 4, COX, C. W., The circulation of the atmosphere 1932 [Atlantic]. over South Africa, So. Africa, Irrig. Dept., Met. Mem., no. 1, 1935, 74 pp. (Prelim, art., EVGENOV, N., Observations hydro-meteorolo- So. Afr. J. Sci., V. 23, 1926.) giques des expeditions hydrographiques. Materiaux de I'Expedition Hydrographique Expedition DANISH to Greenland 1912-1913, de I'Ocean Glacial du Nord, 1910-15. Les Wissenschaftliche Ergebnisse der Ddnischen resultats des observations aerologiques reQues Expedition nach Dronning Louisesland und par les levers de serfvolant sur le navire Quer iiber das inlandeis von Nordgronland hydrographique "Taimyr" faites en 1913- 1912-13 unter Leitung von Hauptmann J. 1915. Leningrad, Admin. Hydr., Sec. Hydro- P. Koch, by J. P. Koch und A. Wegener, Met., 1931. [In Russian.] Meddelelser om Gronland. Bind 75, 1930. the DANISH. Meteorolog. Inst., Resultats des Ra- FERGUSSON, S. P., ed.. Reports of the University diosondages fails a Thornshavn (lies Fa- Greenland Expeditions of of (1926-31) Part I Aerology: Ex- roes) pendant le mois d'Avril 1939, Copen- Michigan — hagen, 1939, 11 pp. peditions of 1926 and 1927-29, Ann Arbor, 1931, 259 DATA from aerological soundings at Fair- p. banks, Alaska during the winters 1936-37 FICKER, H. von, Die Passatinversion, Veroff. and 1937-38, M. W. R., Suppl., no. 40, 35 Met. Inst. Univ. Berlin, Bd. 1, h. 4, pp. 33, pp., 1940. 1936. ) —

192 AIR MASS ANALYSIS

FICKER, H., v., Bemerkung uber den War- HARRISON, L. P., On the water vapor in meumsatz Innerhalb der Passatzirkulation, the atmosphere over the United States east Berlin, Preuss. Akad. Wiss., Phys. Math. of the Rocky Mountains, M. W. R., v. 59, Kl., 1936, 11. 14 pp. pp. 449-472, 1931. FUTI, H., The vertical distribution of tem- HARWOOD, W. A., Upper-air movement in perature in the stratosphere and troposphere the Indian ynonsoons and its relation to the over the earth, Jn. Met. Soc. Jap., v. 15, no. general circulation of the Atmosphere, Mem. 12, p. (45)-(46), 558-572 (tables, cross-sec- India Met. Dept., v. 24, part 8, 1924, pp. tions, bibliog. 249-72. FLOWER, W. D., Temperature and relative HEYWOOD, G. S. P., The upper winds of humidity in the atmosphere over lower Hong Kong, from observations made with Egypt, London, Met. Office, Prof. Notes no. pilot balloons, 1921-1932, Hong Kong, Royal 75 (v. 5), pp. 3-12, 1937. Obsy., 1933, 13 pp. GEORGI, J., Aerologie der hohen Breiten und HIGHTMAN, H. M., Ceiling and visibility in grosse Zirkulation, Arktis, Jahrgang 1, H. the United States: Rocky Mountain states, %, pp. 83-96, 1928. M. W. R., V. 58, pp. 202, 1930. GEORGI, J. und L. Kuhlbrodt-Raehoer, Ho- HILDEBRANDSON, H. H., Resultats des re- henwindmessungen auf Island 1909-192S. cherches emjnrigues sur les mouvements ge- Zusammenstellung und statische Bearbei- neraux de I'atmosphere. Upsala, Soc. Sci., tung von 57^ Pilotwindraessungen aus Island Acta, V. 5, 1918 50 pp. und den Kiistengewdssern..' Hamburg, Aus HUNT, H. A., Australian upper-air work, d. Seewarte, Bd. 51, no. 5, dem Arch. pp. Beitr. z. Phys. d. fr. Atm., Bd. 15, pp. 163- 84, 1932. 169, 1929 (bibliog.). GHERZI, E., The winds and uppier-air cur- HUBERT, H., Les mouvements generaux de the rents along the China Coast and in lair atmospherique au-dessus des Colonies Yangtse Valley, Shanghai, Zi Wei Obs., Ka francaises, Ann. de Phys. du Globe, no. 7, 240 pp., 1931. pp. 1-27 ; cont. in no. 9, pp. 73-83, 1935. GIOVANELLI, J., Les courants aeriens et la JAKL, v.. Ceiling and visibility in the United pressiayi atmospherique en Oceanie Fran- States: Central states, M. W. R., v. 58, no. caise, Annal. de Phys. du Globe, No. 36. 5, pp. 201-202, 1930. 1939, pp. 167-191. JAKL. V. E., An account and analysis of the annees sondages GIOVANELLI, J., Quatre de Meisinger free-balloon flights, M. W. R., v. aerologiques en Oceanie, Annal. de Phys. du 53, pp. 99-107, 1925. Globe, no. 28, pp. 102-125, 1938. JAUMOTTE, J., Structure thermique de la GIOVANNELLI, J. L., Resume des resultats stratosphere jusqu'd 30 km. Gerl. Beitr. des sondages aerologiques effectues en Oce- Geophys. Bd. 50, pp. 403-22, 1937. anic Fran^aise de 19 3U a 1939, Papeete Tahiti, Obs. du Faiere Met.—Phys. du Globe, JAUMOTTE, J., Transformations thermody- namiques la stratosphere et nuages na- 16 pp., 1940. de cres, Belgium, Inst. Roy. Met., Memoires, E., The international kite and balloon GOLD, V. 5, 41 p., 1936. ascents, London, Met. Office, Geophys. Me- Vsber die moirs, no. 5, 1913. KALLIO, N Windverhaltnisse der oberen Luftschichten am aerologischen Ob- GRaFE, H., Tiber Zusammenhdnge zwischen servatoriums Ilmala nebst ubsersichten fur verti- Bodenwind, Luftdruckverteilung und anderen Gegenden, Soc. Sci. Fenn. Comm. kaler Temveraturschichtung in grossen Rdu- Phys. Math. v. 3, no. 3, 1926. 149 pp. ; also der Aquatorzone des Atlantischen Oze- men as Mitt. Met. Inst. Univ. He^s'ngfors, no 3, ans, Ann. d. Hydr., 1939, H. 6, pp. 303-309. 1926 (Contains exhaustive bibliogr. of up-

[GREENLAND] Aerologische Beobachtungen per wind studies down to 1926) ; later study. in Angmagssalik wahrend des Intern. Mitt. Met. Inst. Univ. Helsingfors, No. 7. Polarjahres 1932-33, Kon. Nederlandsch Met. KIDSON, E., The circulation of the atmos- Inst., Ergebn. Aerol. Beob., No. 22A, The phere above Melbourne, QJRMS, v. 54, no. Hague, 1934, 19 pp. (Means publ. by 225. pp. 27-42, 1928. Bleeker, Beitr. Phys. fr. Atmos. v. 23, p. 39-44.) KIDSON, E., Winds in the upper air at Wel- lington, N. Z., London, Met. Off., Note no. GREGG, W. R., aerological survey the An of 15, 8 pp., 1935. United States. Pt. I, Results of observations KOPP, W., ijber die potentielle Temperatur by kites, MWR Suppl. 20, 1922 ; Pt. II, Re- Haupt-inversionen, Z., Bd. 43, H. 12, sults of observations by pilot balloons, MWR der M. Suppl. no. 26, 1926. pp. 471-473, 1926. GREGG, W. R., Monthly and seasonal mean KORFF, S. A. and G. Wagner, La meteorolo- temperatures and relative hum,idities for gia d'el estratosfera en Peru, Serv. Met. de the standard geopotentials for the jieriod of Peru, Lima 1935, 8 pp. the second International Polar Year 1932-33, KUHLBRODT, E., Boden- und Hohenwinde Beitr. Phys. fr. At., Bd. 25, pp. 130-144, der Balkanhalbinsel, Aus. d. Arch. d. Deutsch. 1939, (U. S. data) Seewarte, Jahgang 41, Nr. 3, 37 pp., 1923. GRIMMINGER, G., and W. C. Haines, Mete- KUHLBRODT E. Das stromungsystem der orological results of the Byrd Antarctic Ex- Luft Uber dem tropischen Atlantischen Oze- peditions 192S-30, 1933-35: Tables, MWR. an nach hohenwindmessung der Meteor-Ex- Suppl. 41, 1939, 377 pp. pedition, Zeit. f. Geophys., v. 4, 1928, pp. 385 ff. GUTERMAN, I. G., Some peculiarities of the atmosphere in arctic regions. Trans. Arctic KiJTTNER, J., Die atmosphdrischen Gleichge- Inst., USSR, V. 122, 1938. wichts-Verhdltnisse Uber Lappland im Po- larsommer : ein Beitrag zur Aerologie der GUTERMAN, I. G., Vertical Temperat^^re 98- Gradients above Franz Josiph Land, Met. Arktis. Beitr. Phys. fr. At., Bd. 24, pp. 114, 1938. i. Hydrologia, 1938. no. 6, pp. 56-65 [in Rus- sian]. (Thermal Structure un to 20 Kilo- LANDI, A., II fronte tropicale sul Mediter- meters over Franz Joseph Land) in BAMS. raneo, Rivista di meteorologia aeronautica, V. 19, pp. 433-436, 1938. Rome, An. 3, pp. 3-25, 1939. BIBLIOGRAPHY 193

LARSEN, L. N., Visibility and upper winds RAMANATHAN, K. R., Discussion of results at Auckland, Wellington and Christchurch, of sounding balloon ascents at Agra during N. Z., New Zealand, Met. Off., Note no. 20. the period July 1925 to March 192S and some allied questions, India Met. Dept., LEE, A. W., The relation of the circulation in Memoirs, v. 25, pt. 5, pp. 163-193, 1930. the upper air to a circumpolar vortex, P. Ramakrish- QJRMS, V. 50, 1924, p. 69-74. RAMANATHAN, K. R., and K. nan. Discussion of results of sounding bal- C. M., Summary aerological LENNAHAN, of loon ascents at Poona and Hyderabad during obtained by means kites, air- observations of the period October 192S to December 1931, planes and sounding balloons in the United India Met. Dept., Memoirs, v. 26, pt. 4, pp. R., Suppl., no. 38, 65 1938. States, M. W. p., 51-187, 1934. D. M., Ceiling and visibility in the LITTLE, RAMANATHAN, K. R., and K. P. Ramakrish- States: Pacific coast states, M. W. United nan. The general circulation of the atmos- 203-204. R., V. 58, pp. phere over India and its neighbourhood, MALURKAR, S. L., On the extreme dryness India Met. Dept., Memoirs, Delhi, v. 26, pt. observed at KodaikanaZ during the winter 10, pp. 189-245, 1939. months, India Met. Dept., Scientific Notes, RAY, C. L., Free-air winds at San Juan, P. V. 4, no. 43, pp. 137-144, 1932. R., MWR, V. 59, 414-16, 1931. Fritz, Der Jahresgang der Tempera- M6LLER, REED, T. R., Further observations on the tur in der Stratosphare, MZ, Bd. 55, pp. North American high-level anticyclone, M. 161-170, 1938. abstract in W. R., V. 65, pp. 364-6, 1937 ; M6LLER, F., ijber horizontale Austauschwar- BAMS, V. 18, pp. 297-8, 1937. mestrome iiber Mitteleuropa und ihre Verdn- REED, T. R., The North American high-level derung mit der Hohe, Beitr. z. Phys. d. fr. anticyclone, M. W. R., v. 61, 1933. Atm., Bd. 22, pp. 46 ff., 1935. REED, T. R., Thermal aspects of the high- P. A., Results of radiomete- MOLTCHANOV, level anticyclone, M. W. R., v. 67, pp. 201- orograph soundings during 1930-36 in the 203, 1939. S. and the Arctic, BAMS, v. 18, U. S. R. Troposphdre pp. 322-325, 1937. REGER, J., Die Grenze zwischen und Stratosphare. Arbeiten d. pr. Aeronaut. MiJLLER, Fritz, Die Stromungen der Atmos- Obs. Lindenberg, Vol. 16, pp. E2-6, 1930. phdre iiber Teneriffa, Veroff. Geophys. Inst. mittlere jdhrliche Tempera- Univ. Leipzig, Bd. 8, pp. 133-179, 1936. REGER, J., Der turgnag iiber Lindenberg, Beitr. Phys. fr. NAKAYA, U., Monthly normals of isobars in At., Bd. 23, H. 3, pp. 195-198, 1936. Japan at 3000 m, Tokyo Univ., Jn. Faculty meteorological observations taken Sci., Sect. I. no. 1, 1927, pp. 301-312. REPORT on during the Polar Year 1932-33. Pretoria, NOHASCHECK, H., Die thermische Schich- (Union So. Africa, upper-air data). tung der Atmosphdre iiber Batavia, Beitr. halbjahrige Luftzirkulation Phys. fr. At., Bd. 20, H. 1, pp. 1-8, 1932. REUTER, F., Die im NO-Passatgebiet des Nordatlantischen NOTH, H., Untersuchung iiber die Zusam- iiber Teneriffe, Ann. d. Hyd., v. 67, menhdnge zwischen stratosphdrischer Druck- Ozeans 1939, 57-67. verteilung, Luftdruckmittelwerten, Hohdn- p. the derungen der Hauptisobarenflachen und der RILEY, J. A., Ceiling and visibility in Niederschlagsarm.ut, Deutsch. Flugwetter- United States: Southeastern states, M. W. 1930. dienst, Erfahrungsberichte, Sonderband 3, R., V. 58, pp. 199-201, pp. 156-160, 1930. ROEDIGER. G., Der Europdische Monsun, Inst. Veroff., 2. PATTERSON, J., Upper-air investigation in Leipzig, Univ. Geophys. 119-177 (see Canada, Part 1, Observations by registering Serie. Bd. 4, Hft. 3, 1929, pp. balloons, 127 pp. Ottawa, Gov't, print, bur., also MZ, V. 56, 1939, p. 149-52.) 1915. ROLF B., Lancers de ballons-sondes d'Obisko, Met.-Hydrogr. PEPPLER, W., Studie iiber die aerologischen de 1921-29, Medd. fr. Stat. Verhdltnisse im Nordquadranten der Mittel- Anst., Stockholm, v. 5, no. 5, 1932. meerdepressionen, Gerl. Beitr. Geophys., Bd. SAMUELS, L. T., Temperature distribution 34, pp. 223-245, 1931. up to 25 kilometers over the Northern PEPPLER, W., Die thermische Schichtung der Hemisphere, M. W. R., v. 57, p. 382, 1929. Atmosphdre, Beitr. v. Phys. d. fr. At., Bd. SEILKOPF, H., Hdhenwindmessungen auf 11, H. 2, pp. 79-95, 1924. deutschen Handelsschiffen. Der Pilote, (Publ. PETERS, S. P., Some observations of upper of the Deutsche Seewarte) 1930. air temperature London, Met. Office, in Iraq, SEN S N., On the distribution of air density Prof. Notes, no. 2-10, 1930. 59 (v. 4), pp. over the globe, QJRMS, v. 50, 1924, p- PETERS, S. P., Some upper-air observations 29-52. over lower Egypt, London, Met. Office, Geo- SERRA, A. B., La circulation generate de I'A- phys. Memoirs, no. 56, (v. 6) pp. 3-44, 1932. merique du Sud, Rio de Janeiro, Serv. Nac. PETITJEAN, M. L., Dix annees de sondages a de Met., 1939, 17 pp., [Important paper.] Alger (191S-1928), La Meteorologie, pp. 214- SERRA, A. B., and L. D., Barbosa, The nor- 229, avril a juin 1929. mal atmosphere above Alegrete, Brasil, Min. PIIPO, A. F., Analysis of the Madison, Wis., da agric, Servicio Nac. de Meteorologia, aerological data, with an application of the 1939, 20 pp. Bjerknes Theory, M. W. R., v. 56, 47-53, pp. SERRA, A. B., Secondary circulation of south- 1928. disc, by Rodewald, Ann. d. Hyd., (Cf. ern Brasil, Rio de Janeiro, 1938, 29 pp. tables, 558-60.) 1938, pp. diagrs. PROUD, S., Upper winds at Kingston, Ja- SHAW, N., Manual of meteorology : volume maica, London, Met. Office, Prof. Notes no. 2 — Comparative meteorology. University (v. 2-26, 1937. 78, 5), pp. Press, Cambridge 472 pp., 1936. [Contains [RADIOSONDES] Isoplethes de temperature. valuable mean charts and tables and in the La Met., Jan. -Feb. 1938 and later issues appendix a bibliog. of upper air data by (cross sections of isotherms day by day from countries which is the only guide to such soundings made at Trappes, to 15-18 km). material.] )

194 AIR MASS ANALYSIS

SIMPSON, G. C, The south west Monsoon, TRELOAR, et al.. Weather conditions affecting QJRMS, V. 47, pp. 151-172, 1921. aviation over the Tasman Sea, Australia, SINODA, K., Monthly normal isobars at jOOO Comm. Bur. Met., Bulls. 24 and 25, Mel- and 6000 m levels over Japan and its vicin- bourne, 1938. ity, Tokyo Univ., J. Fac. Sci. Sect., I, no. TU, Changwang, Results of aerological inves- 1, 1927, pp. 313-317. tigations in China, Beitr. Phys. d. fr. Atm., SPILHAUS, A., Results of aerological investi- Bd. 25, pp. 233-240, 1939. gations in South Africa, Beitr. z. Phys. d. U. S. NAVY, Hydrographic Office, Pilot fr. At., Bd. 24, pp. 228-231, 1937. Charts of the Upper Air: North Pacific STAFF, Helmut, Der tagliche Luftdruck- und Ocean: North Atlantic Ocean. (Monthly). Temperaturgang in der freien Atmosphdre VALENZUELA, del Rio, J., Le vents a di- in seiner Abhdngigkeit von den Jahreszeiten, verse hauteurs au-dessus de Santiago (Chile), Diss. Fr.-Wilhelms-Univ. Berlin, 1934, 41 pp. in : Publ. No. 41 de Secret, de L'Organ. Met. STEVENS, L. A., Upper-air winds over north- Intern., Leyden, 1939, p. 134-9. ern Alaska during the International Polar S. P., Daily variations Year. August 1932-August 1933, inclusive, VENKITESHWARAN, of temperature and pressure at different M. W. R., V. 62, pp. 244-247, 1934. levels over Agra associated with passage of STONE, R. G., Analysis of resultant winds western disturbances. India Met. Dept., Sci- aloft at San Juan, P. R., BAMS, v. 21, 1940, entific Notes, v. 7, no. 73, pp. 59-63, 1937. p. 111-112. VOGEL, H., Die atmospharische Zirkulation K., and J. SUR, N. C. Roy, On some charac- iiber Australien Mitteilungen Geogr. Gesell. teristics of the tropopause and upper tropo- in Miinchen, v. 22, h. 2, pp. 181-238, 1929. sphere over North-west India,, India Met. Dept., Sci. Notes, v. 5, no. 48, pp. 19-31, WAGNER, A., Klimatologie der freien Atmos- 1931. phdre, Teil F, Bd. 1, of Handbuch der Kli- matologie, ed. by W. Koppen and R. Geiger, SUTTON. L. J., The upper currents of the Berlin, Borntraeger, 1931. 70 pp. [Extensive atmosphere in Egypt and the Sudan, Egypt, summary of all upper air data for the world Phys. Dept., Paper no. 17, 136 pp., 1925. down to 1931.] SVERDRUP, H. U., Discussion of meteorology A., Results observations in "The Norwegian North Polar Expedition WALTER, of on the direction and velocity the upper air cur- with the MAUD, 1918-1925", "Scientific Re- of rent over the South Indian Ocean, London, sults", V. 2, Part 1. Bergen, 1933. Met. Off., Geoph. Mem., v. 4, no. 39, pp. SVERDRUP. H. U., Der nordatlantische _ Pas- 1-32, 1927. sat, Veroff. Geophys, Inst. Univ. Leipzig, WAGNER, A., Zur aerologie des indischen Bd. 2, pp. 1-96, 1917. Monsuns, Gerl. Beitr. Geophys., Bd. 30, pp. THOMSON, A. : Upper-Air Currents at 196-238, 1931. Apia. N. Z. Dept. Sci. Ind. Res., Wellington,

1929 ; later data in Annual Rept. Apia Obsy, WANGENHEIM, G. I., Meteorolonical regime 1932, 34, '38. of the region of Franz-Joseph Land during the period Trans. Arctic THOMSON, A., Upper-air currents at Hono- warm of the year. Inst, of (Leningrad), v. 103, 1937, lulu. T. H., M. W. R., V. 56, pp. 496-498, USSR 1928. 64 pp. TOMMILA, M.. Niilo R. and Vilho Vaisala, WEI, Y., A study of the upper-iir circulation Aerologische Beobachtungen mit Radiosonden over central China by means of pilot balloons im Sonimer 1937 in Spitzbergen und in Pet- (abstract in English). Met. IMag. (China), samo, Ann. Acad. Sci. Fennicae, Ser. A, v. V. 13, no. 3, p. 171, March, 1937. 53, no. 5, (Repr. as Mitteil. des Met. Inst. H., Observed transverse circula- der Univ. Helsinki, no. 41, 1939). 50 pp. WEXLER, tions in the atmosphere and their cHm,atoloa- TRUTNJEWA, W. W. und Keramyschew, ical implications. Mass. Inst. Tech., Ph.D. Ergebnisse der aerologischen Beobachtungen thesis, 1939 [not yet pub'd.]. in der Mongolei in Urga (Ulan-Ba.tor- Choto), Irkutsk, Mag. und Met. Obs. Ver- ZISTLER, P., Miichener Registrierballonauf- handlungen, No. 2-3, pp. 173-174, 1928. [up- steige iiber SO km. HShe, Deutsches Met. per winds) Jahrbuch Bayern, 1934, Anhang C, 11 pp.

Average (Statistical, or Schematic) Structure and Movement of Cyclones and Anticyclones; Models

ABILD, Bruno, Betrachtungen iiber meteor- BAUGHMAN, F. A., Winter cold fronts at oloaische VerhiUtnisse an Fronten, Diss., Cleveland airport, BAMS, v. 20, pp. 48-49. Chr. Albrechts-Univ., Kiel, 1937. 49 pp. 1939. aNGSTRoM, a.. Die Variation der Nieder- BAUR, F.. Polarfront und Aquatorialfront, schlag sintensitdt bei der Passage von Re- Ann. d. Hydrog., Bd. 51, H. 12, pp. 284-287, gengebieten und einige Folgen betreffs der 1923. Struktur der Fronten, MZ, Bd. 47, pp. 177- BECKER, R., Der Einfluss der Re^'bung auf 181, 1930. die Form der Luftkorpergrenzfldchen bei BALCKE, Erwin, Untersuchung abnorn hoher Kdltevorstossen und RiXckziXaen, Ann. d. Temperaturen in Norddeutschland. Aus d. Hydr., 1932, H. 12, pp. 489-495. Arfh. d. Deutsch. Seewarte, Bd. 57, Nr. 4, BILHAM, E. G.. Isallobars of moving circular 1937, pp. 1-38. depressions. Geog. Ann., v. 3, pp. 336-357, 1921. BAMFORD, A. J., Notes on the climate of ^vp-fo/yn f^'"ii'on with special reference to the BERGERON, T. (see refs. under sect. A 2, I'VP^r winds at Colo~nb". Cilombo, Ceylon, above. J. V. 173-205, 1929. Sc, Sec. E, 1, pp. BJERKNES, J., Mildner, P., Palmen, E. und BANERJI, S. K., and G. T. Walker, Vortices Weickmann, L., Synoptisch-aerologische Uv~ on the monsoon front. Nature (London), v. tersuchung der Weiterlage wdhrend der 14, pp. 88-93, 1928. internationalen Tage vom 13. bis IS. De- BIBLIOGRAPHY 195

zember 1937, Leipzig, Univ. Geophys. Inst., 1919, London, Met. Office. (Abstr. and disc. Veroffentlichungen, Zweite Serie, Bd. 12, h. by W. R. Gregg, MWR, Sept. 1919, pp. 1, 107, pp. 1939. 644-649.) BJERKNES, J., Investigations of selected DINES, W. H., The Connection between pres- European cyclones by means of serial as- sure and temperature in the upper layers of cents, Geofys. Publ., V. 11, no. 4, 1935, 18 the atmosphere, MWR, v. 50, 1922, pp. 688- pp. 642. BJERKNES, J., and E. Palmen, Investigation DINIES, E., Der Aufbau von Steig-und Fall- of selected European cyclones by means of gebieten, Reichsamt fiir Wetterdienst, Wis- serial ascents. Case U: Feb. 15-17, 1935, sensehaftliche Abhandlungen, Bd. 3, Nr. 3, Geofys. Publ., V. 12, No. 2, 1937, 62, pp. pp. 1-16, 1937. (Disc, by Scherhag, Ann. d. Hyd., 1938, pp. DINIES, Ervvrin, Die Steuerung von Wdrme- Ciel et 198-201.) Abstr. by van Mieghem, wellen, MZ, Bd. 53, pp. 81-84, 1936. Terre, v. 54, 1938, pp. 337-56. DOUGLAS, C. K. M., Aspects of surfaces of BJERKNES, J., On the structure of moving discontinuity, QJRMS, 55, pp. 123-152, 1929. cyclones, Geofys. Publ., v. 1, No. 2, 8 pp., DOUGLAS, C. K. M., Deepening of depressions 1918, Repr., M. W. R., Feb., 1919, pp. 90-99. by day and night, Met. Mag., Mar., 1931, BJERKNES, J., and H. Solberg, Life Cycle of pp. 39-41. cyclones and the polar front theory of at- DOUGLAS, C. K. M., A discussion of tem- mospheric circulation, Geofys. Publ., v. 3, peratures at U km at Reykjavik and Duxford No. 1, 18 pp., 1922, Rev'd in M. W. R., during the polar year. Met. Mag., 1933, pp. Sept., 1922, pp. 468-474. [Of. : K. Wegener, 253-256 ; A further discussion of . .: id., Beitr. Phys. fr. Atmos., v. 9, 1920, p. 78-90.] Feb., 1935, pp. 7-10. BJERKNES, J., et H. Solberg, Les Coiiditions DOUGLAS, C. K. M., Divergent isobars and tions Tneteorologiques de formation de la winds. Met. Mag., v. 73, pp. 177-178, 207, France, Office Nat. Met., Memorial, pluie, 1938. no. 6, 81 pp., 1923. (Transl. of Met. conditions for the formation of rain, Geofys. DOUGLAS, C. K. M., Fronts and depressions. Met. Mag., v. 71, 34-39. Publ., V. 2, no. 3, 1921.) March, 1936, pp. Cirrus BJERKNES, v., Ein prognostisches Prinzip DOUGLAS, C. K. M., Movements of clouds in relation to fronts, QJRMS, v. 57, der dynamischen Meteorologie, Ber. d. math.- 1931, 90-2, (also see Met. Mag., May phys. Kl. sach. Gesell. Wiss., 1917. (abstr. in p. 1932, p. 89-91.) M.Z. 1917, p. 345). DOUGLAS, C. K. M., On the relation, between BROOKS, C. F., The distribution of snowfall temperature and pressure in the tropo- in cyclones of the eastern U. S., MWR, v. sphere. Royal Met. Soc, Memoirs, v. 3, no. 42, 1914, p. 318-30. 29, pp. 159-168, 1930. BROOKS, C. F., Microbarometric oscillations C. K. M., On the relation between at Blue Hill: Fart 3—Air waves at Blue DOUGLAS, temperature changes and wind structure in Hill, Dec. 17-18, 1931, BAMS, v. 16, p. 159- the atmosphere, Roy. Met. Soc, Mem- 1935. upper oirs, v. 1, no. 7, pp. 95-104, 1927. BRUNT, D., and C. K. M. Douglas, The modi- C. K. M., On the relation between fication of the strophic balance for changing DOUGLAS, the source the air and the upper air tem- pressure distribution, and its effect on rain- of perature up to the base of the stratosphere, fall, Roy. Met. Soc, Memoirs, v. 3, no. 2, QJRMS, V. 51, July, 1925, pp. 229-23a pp. 29-51 ; 198-201, 1929. (diag. ). BUGAIEV, V. A., On the relation of cyclonic K. M., Some facts and theories, trajectores with the position of arctic front DOUGLAS, C. upper atmosphere, QJRMS, v. 61, in winter, Moscow, Met. Hydrol., 1936, no. about the no. 258, pp. 53-70, 1935. 8, pp. 11-18. C. K. M., Tennperature variations BYERS, H .R., The ascent of air at warm DOUGLAS, in the lowest four kilometers, QJRMS, v. 47, fronts. QJRMS., v. 63, July, 1937, p. 431. pp. 23-43, 1921. BYERS, H. R., Divergence and deepening of C. K. M., Rainfall from above extra-tropical cyclones, QJRMS, v. 66, Sup- DOUGLAS, 6000 in relation to upper winds and plement, pp. 60-67, 1940. feet, fronts, QJRMS, v. 62, pp. 207-218, 1936. CECCHINI, E., Stdl'andamento della tempara- K. M., Some factors influencing tura eguipotenziale nei bassi strati della tro- DOUGLAS, C. the development and occlusion of warm, posfera a Vigna di Valle, Rivista di Met. sectors, QJRMS, v. 65, pp. 525-531, 1939. Aeronautica, Rome, anno. 3, no. 4, pp. 3-8, 1939. Disc, id; Jan. 1940, p. 79.) CHAO, Shu, The Relation between wind direc- DOUGLAS, C. K. M., Further researches into tion and weather, Tsing Hua Univ. Met. the European upper air data, QJRMS, v. Obsy., Supplement to Quarterly Met. Bull., 50, 1924. p. 339-64. pp. 5-12, 1932. (In English) DUFOUR, L., Etude du vent geostrophigue et CHAPMAN, E. H., The relationship between du vent de gradient a Uccle, Ciel et Terre, pressure and temperature at the same level v. 53, pp. 1-10 ; 75-80, 1937. in the free atmosphere. London, Roy. Soc, DURST, C. S., The form of cold fronts, Proc, V. 98, A., pp. 235-248, 1920. QJRMS, V. 58, July, 1932, pp. 302-303. DINES, L. H. G., An analysis of the changes DURST, C. S., The wind structure beneath of temperature with height in the strato- warm fronts, QJRMS, v. 64, no. 276, pp. sphere over the British Isles, Mem. Roy. 516-522, 1938. Met. Soc, V. 2, no. 18, pp. 137-151, 1932. EGERSDoRFER, L., Korrelationen zwischen DINES, L. H. G., A comparison between the Luftdruck und Temperatur vom Boden bis geostrophic wind, surface wind and the up- 9 km Hohe iiber MUnchen, Deutsches Met.

per winds from pilot ballons, at Valentia, Jrb. f. Bayern, 1930. Anhang J, 5 pp ; Par- Met. Off. Lond., Prof. Notes, no. 83, 1938. tielle Korrelationen .... id, 1931, D, 7 pp. DINES, W. H., The characteristics of the EKHOLM, N., Wetterkarten der Luftdruck- free atmosphere, Geophys. Memoirs, no. 13, schwankungen, M. Z., v. 21, pp. 345-357, ,

196 AIR MASS ANALYSIS

1904 ; further, MZ, 1906, p. 228 ; 1907, pp. May, 1935, pp. 87-88 ; Douglas, Sept., 1935, 1, 102, 145. 189-190. EXNER, F. M., Zur Frage, ist der ilberadiaba- GOLD, E., Barometric gradient and wind tischen Gradienten reell? WL, Bd. 36, pp. force (Rept. to the Director of the Met. 245-253, 1919. Office on the calculation of v^ind velocity from pressure distribution and on the varia- EXNER, F. M., On the str-ucture of anticyclones and cyclones in the stratosphere over tion of meteorological elements with altitude), London, Met. Office, Pub. 190, 1908. Europe, M. W. R., v. 49, pp. 653-655, 1921. GOLDIE, A., Depressions as vortices. Lon- EXNER, F. V, Studien iiber die Ausbreitung don, Met. Off., Geophysical no. kalter Luft auf der Erdoberfiache, Sitzb. Memoirs 79, 1939. Wien. Akad. Wiss., Abt. Ila, v. 127, H. 6, A. H. R., determining pp. 1-53. 1918 ; see also id., v. 120, 1911, p. GOLDIE, Circumstances 1411; V. 131, 1922, p. 366; v. 133, 1924. the distribution of temperature in the upper air under conditions of high and low EXNER, F. M., Vber dew Aufbau hoher Anti- barometric pressure, QJRMS, v. 49, no. 205, zyklonen und Zyklonen in Europa, M. Z., pp. 6-20, 1923. Bd. 38, pp. 296-299, 1921. GOLDIE, A. H. R., Kinematical features of S. P., Exploration of the air FERGUSSON, Depressions, London, Met. Off., Geophys. means kites, Ann. Astron. Obsy. Har- by of Memoirs, No. 72, 43 pp., 1937. vard College, V. 42, pt. 1, Append. B, pp. 41-128, 1896. GOLDIE, A. H. R., Some characteristics of the mean annual circulation over the British FERGUSSON, S. P., and H. H. Clayton, Ex- Isles, QJRMS, v. 62, pp. 81-103, 1936. ploration of the upper air by means of ballons-sondes at St. Louis in the years 1904-07, G6LLES, F., Untersuchungen iiber den Luft- Ann. Astron. Obsy. Harvard College, v. 63, druckgang bei Kdltewellen im Gebiete des 97-107, pt. 1, pp. 1-92, 1909. kaspischen Meeres, MZ, Bd. 39, pp. 1922. FICKER, H. von, Bemerkungen Uber die Agua- torialfront, M. Z., Bd. 41, pp. 202-206, 1924. GREGG, W. R., The relations between free air temperatures and wind directions, MWR, v. FICKER, H. von. Die 'knderungen der Grosse 52, pp. 1-18, 1924. der Luftdruckschwankungen in den untersten Schichten der Atmosphdre, M. Z., Bd. GRIMMINGER, G., The intensity of lateral in the as 37, pp. 145-151, 1920. mixing atmosphere determined from isentropic charts, Trans. Amer. Geo- FICKER, H. von, Der Transport kalter Luft- phys. Union, 1938, pt. 1, p. 163. massen iiber die Zentralalpen, Denks. Akad. Stanislav, Die Rdumliche Vertei- Wiss. Wien, v. LXXX, 1905. (See also, HANZLIK, lung der meteorologischen Elemente in den MZ. 1910, pp. 1-12). Antizyklonen (ein Beitrag zur Entwicklungs- FICKER, H. von., Bemerkungen iiber die geschichte der Anticyklonen), Akad. der Konstitution zusammengesetzter Depressio- Wiss., Denkschriften der Math-naturw. 65-70, 1921. nen, M. Z., Bd. 38, pp. Klasse, Bd. 84, 94, pp., 1908. FICKER, H., KdlteeinbriXche Uber Lindenberg, HANZLIK, S., Beitrage zur Entwicklungs- MZ., Bd. 39, pp. 65-72, 1922. qeschichte der Zyklonen, Akad. Wiss., Wien, FICKER, H. von, Beziehungen zwischen An- benkschrift., 1912, pp. 67-128. der Tempera- derungen des Luftdruckes und HARIHARAN, A. S., Inversions of lapse rate tur in den unteren Schichten der Tropos- over Karachi, India Met. Dept. Sci. Notes, der Depressionen) phare (Zusammensetzung V. 5, no. 56, 1934. Ber. d. Akad. Wiss. Wien., Math.-Na- Sitz. HARTMANN, W., Schichtgrenzen und Wolken- turw. kl., Abt. Ila, Bd. 129, pp. 763-810, hohen im nordwestdeutschen Flachland, MZ, 1920 (abstr. MWR, 1921, p. 652). Bd. 49, pp. 459-466, 1932. FICKER, H. von, Maskierte KdlteeinbriXche, HAURWITZ, B., Beziehungen zwischen Luft- M. Z., Bd. 43, pp. 186-188, 1926. druck- und Temperaturanderungen: Ein FICKER, H. von, Polarfront, Aufbau, Entste- Beitrag zur Frage des "Sitzes" der Luft- hung und Lebensgeschichte der Zyklonen, druckschwavkungen, Veroff. Geophys. Inst. Z., 65-79, 264-267, 1923 [rev. M. Bd. 40, pp. Univ. Leipzig, Bd. 3, pp. 267-335, 1927. of literature]. HAURWITZ, B., Pressure and temperat%irc FUJIWHARA, S., Examples of cyclones and variations in the free atmosphere and their and pure depressions of pure thermal of effect on the life history of cyclones, BAMS, Japan, Ser. dynamical origin, Jn. Met. Soc, V. 20, pp. 282-287, 1939. 2, V. 3, 1925, pp. 1-5. HAURWITZ, B., Symmetry-points in the air- FUJIWHARA, S., Short note on the behavior pressure. Trans. Amer. Geophys. Union, vortices, Proc. Phys. Math. Soc. or two 1936, pt. 1, pp. 118-120. Japan, Ser. 3, v. 13, no. 3, 1931. HAURWITZ, B., and E. Haurwitz, Pressure FUJIWHARA, S., et al.. On vorticity in the and temperature variations in the free atmosphere as a weather factor, J. Fac. atmosphere over Boston. Harvard Met. Sci., Imp. Univ. of Tokyo, Sec. 1, v. 3, pt. Studies, no. 3, 71 pp., 1939. 2, pp. 65-106, 1935. HAURWITZ, B., and W- E. TurnbuU, Rela- GEORGII, W., Der Luftaustausch zwischen tions between interdiurnal pressure and niederen und hoheren Breiten iiber dem ost- temperature variations in troposphere and lichen Mittelmeer. Beitr. z. Phys. d. fr. Atm., stratosvhere over North America. Canadian Bd. 15, pp. 61-88, 1929. Met. Memoirs, v. 1, no. 3, pp. 67-92, 1938. GIBLETT, M. A., Line-squalls, M. W. R., v. HESSELBERG, Th., Die Luftbewegungen im 56, pp. 7-11, 1928. Cirrusniveau. Leipzig, Univ., Geophys. Inst., VerofF., 2. Serie, Spezialarbeiten aus dem GOLD, E., Rain in advance of true "warm Inst., Heft. 73 1913. front" rain. Met. Mag., Nov., 1934, pp. 235- Geophs. 2, pp., 237 T further remarks under same title by HOFFMEISTER. J.. Vsber die Struktur der Ockenden and Read, Id., Aug., 1935, pp. NiederscMagsintensitdt bei langandauernden

160-161 ; Bailey, Dec, 1934, p. 264 ; Daking, niederschldaen. Preuss. Met. Inst., Bericht

Mar., 1935, pp. 40-42 ; Dewar and Douglas, Tiber die Tatigkeit, 1932, pp. 111-120. :

BIBLIOGRAPHY 197

HOFFMEISTER, H., ijber die ijbergangs- M6LLER, F., Hohenwindmessungen und hori- schicht zwischen verschieden temperierten zontales Temperaturfeld, Beitr. Phys. fr. At., Luftmassen, Preuss. Met. Inst., Bericht iiber Bd. 22, pp. 299-307, 1935. die Tatigkeit, 1928, pp. 111-120. M6LLER, F., iJber die pseudopotentielle Teni- HOFFSTEDT, H., Korrelationen zwischen peratur an Inversionen, MZ, 1929, h. 6. Teniperatur Luftdruck, und Tropopausen- MOLTCHANOV, P. A., Concerning the aero- hohe. Mitt. d. Met. Inst., Univ. Helsingfors, logical scheme of the structure of the at- no. 1935. 27, mosphere, Moscow, Met. Hydrol., 1937, no. HOLZMAN, B., Detailed characteristics of •i-5, pp. 48-66. surface fronts, BAMS, v. pp. 155-159, 18, MOLTCHANOFF, P. A., On the aerological 19S7. scheme of the atmosphere structure during IIDA, T., and T. Kinka, On the wind rose of the passage of the warm and cold air masses meteorological elements on Mt. Tukuba, Jn. Moscow, Met. Hydrol., 1936, no. 9, pp. 3-9. Met. Soc. Jap., v. 16, no. 10, 1938, p. (36). MOLTCHANOFF, P. A., On the aerological ISHAQUE, M. A comparison of upper and scheme of the atmospheric structure during gradient winds at Agra and Bangalore, In- the passage of the warm and cold air masses dia Met. Dept. Sci. Notes, v. 1, no. 1, 1928. Un. Geod. et Geophys. Intern., 6ieme Ass. KANITSCHNEIDER, Beitrdge zur Mechanik Gen., Edinbourgh, Sept., 1936, Proces ver- des Fohns, Beitr. Phys. fr. At., v. 18, pp. baux de L'Assoc. de Met., part 2, Mem. et Disc, 120-130. 27-49, 1932 ; v. 24, pp. 26-44, 1938 ; v. 25, pp. pp. 49-58, 1939. NAMIAS, J., Structure and maintenance of KHANEWSKY, W., Zur Frage iiber die Kon- dry-type moisture discontinuities not devel- stituiion und Entstehung hoher Antizyklo- oped by subsidence, M. W. R., pp. 352-358,. nen, MZ, Bd. 46, pp. 81-86, 1929. 1986. KOHASI, Y., and K. Takase, On the amal- NAMIAS, J., Subsidence within the atmos- gamation of cyclones, Jn. Met. Soc, Jap., v. phere. Harvard Meteorological Studies, No. 15, no. 7, 1937, p. (27). 2, 1934, Cambridge. Abstr. BAMS, v. 17, 20-21, prelim, art.. Trans. K6PPEN, W., Entwicklung der Temperatur- pp. 1936; Am. Geophys. Un., 1934, pp. 105-114. Inversionen, M. Z., Bd. 28, pp. 80-81, 1911. NAMIAS, J., Isentropic Analysis, Art. in und F. Wedemeyer, Beziehungen X K6PPEN, W. this zwischen Teniperatur, Luftdruck und Hohe booklet. der Troposphdre im Euroiodischen Flach- NEWNHAM, E. V., Classification of synoptic lande, MZ, Bd. 31, pp. 1-15, 75-87, 1914. charts for the North Atlantic for 1896-1910, KOPPEN, W. Die haufigsten Druckverteilun- Geophys. Mem. Met. Off., No. 26, London, gen und Luftstromungen auf dem Nordatlan- 1925. tischen Ozean und der Luftverkehr, Ann. PALMbN, E., Die Luftbewegung im Cirrusni- d. Hyd., Bd. 56, H. 2, 1928, pp. 41-47. veau iiber Zyklonen, M. Z., Bd. 48, pp. 281- 1931. KUSAKABE, H. and T. Muto, The phenom- 288, enon of the inhibitory effect of strong winds PALMeN, E., iJber die Bewegung der ausser- on rainfall, Tokyo, Univ. Faculty of Sci., tropischen Zyklonen, Mitteilungen des Met. J., Sect. 1, V. 1, pt. 12, pp. 465-480, 1929. Inst. Univ., Helsinfors, no. 4, 102 pp., 1926. LAMMERT, Luise, Der mittlere Zustand der PALMeN, 'Ei.,Versuch zur Analyse der dynam. Atmosphdre bei Siidfohn, Leipzig, Univ., Druckschwankungen in der Atmosphdre, Geophs. Inst., 2. Serie Spezialarbeiten, Bd. Beitr. z. Phys. d. fr. Atm., Bd. 19, pp. 55-

. .2, Heft, 7, pp. 261-322, 1920. 70, 1932. LEMONS, H., Some meteorological aspects of PALMeN, E., Registrierballonaufsteige in Nebraska tornadoes, M. W. R., July, 1938, einer teifen Zyklone, Soc Sc Fenn., Com- pp. 205-208. (Excerpts in: BAMS, Feb. ment. Phys.-math., Vol. 8, No. 3 (Helsing- 1939, p. 51). fors) 1935, 32 pp.; also in Mitt, des Met.- MAL, S., S. Basu and B. N. Desai, Structure Inst. der Univ. Helsingfors, No. 26. Abstr. and development of temperature inversions in M Z, 1935, pp. 17-22. in the atmosphere, Beitr. z. Phys. d. fr. PALMeN, E., Zur Frage der Temperatur~, Atm., Bd. 20, pp. 56-77, 1933. Druck- und Windverhaltnisse in den hoheren. LINDHOLM, F., Sur la structure thermique teilen einer okkludierten Zyklone, M. Z., Bd. de I'atmosphere au-dessus de la Suede me- 53, pp. 17-22, 1936. ridionale sondages faits par avion en 19tU PALMER, Andrew H., Pressure oscillations of et 1925, Stockholm, Met.-Hydro. Anstalt, short wave-length. Blue Hill Met. Obsy., Ob- Meddelanden, Bd. 3, no. 10, 1927, 41 pp. servations, 1911, pp. 210-229. McADIE, The Winds of Boston and vicinity. PEPPLER, W., Aerologische Studien iiber Blue Hill Met'l .Obsy., Observations and In- Temperaiur und Windrichtung, 1. Mitt. vestigations, 1916, pp. 211-231, 1917, pp. 28- Die Mitteltemperatur der Windrichtungen, 46. Beitr. z. Phys. d. fr. Atm.. v. 14, pp. 278- MAHALANOBIS, P. C, On the seat of ac- 290, 1928. tivity in the upper air, Mem. Indid Met. PEPPLER, W., Die Aend^ ungen der Feuch- Dept.. V. 24, no. 1, 1923 10 pp. tigkeit iiber dem Bodensee bei Wdrme-und J. Van, protection meteorolo- MIEGHEM, Une Kdlteeinbriichen, Beitr. Phys. d. fr. Atmos., gique de la navigation aerienne a haute al- Bd. 14, 1928, pp. 131-137. titude est-elle necessaire, Ciel et Terre, 1940, no. 1, 5 pp. PEPPLER, W., Nordliche Winde und Stauwir- kungen iiber dem Alpenvorland, Beitr. Phys. MICHEL, W., iJber einige aerosynoptische fr. At., Bd. 138-146, Merkmale der Anderungen barischer Gebiete, 14, pp. 1928. Recueille de Geophysique, v. 5, h. 3, 1932. PEPPLER, W., Starke Wdrmeeinbriiche in der (Abstr. and comment by Koppen, Ann. d. freien Atmosphdre iiber dem Alpenvorlande, Hyd., 1933, p. 374; Rodewald, id., 1938, p. MZ, Bd. 50, pp. 172-175, 1933. 557.) PEPPLER. W., vber das Vorkommen markan- MOESE, O., and G. Schinze, Zur Analyse von ter Windschichten im, unteren Teil der Tro- Neubildungen. Annalen d. Hydrogr. u. posphdre, Beitr. Phys. fr. At., Bd. 17, pp.. Marit. Met., Bd. 57, Hf. 3, pp. 76-81. 1929. 235-240, 1931. .

198 AIR MASS ANALYSIS

PEPPLER, W., uber die siidlichen Luftstro- Station'dre warme und kalte Antizyklonen in mungen auf dem Sdntis und in der freien Europa, Diss. Leipzig, Wurzburg, 1931 ) Atmosphdre iiber dem Bodensee, Beitr. Phys. SAITO, H., Der Zusa?nmenhang zwischen der fr. At., Bd. 22, pp. 1-11, 1935. fortpflanzen der barometrischen Minima PEPPLER, W., ijber einige Beziehungen zwis- under der Luftbewegung im Cirrusniveau, chen Temperatur und Wind in den unteren Jn. Met. Soc. Jap., v. 15, no. 4, 1937, p. Luftschichten iiber der flandrischen KUste, (15). Beitr. Phys. fr. At., Bd. 18, pp. 209-218, SAMUELS, L. T., A Summary of aerological 1935. observations made in well-pronounced highs PEPPLER, W., Vergleichende Untersuehung and lows, MWR, v. 54, 1926, pp. 195-213. iiber die aerologischen Messungen, besonders SATO, Z., Correlation between the atmospheric der Temperatur, an den deutschen aerolo- pressure and temperature on the top of Mt. gischen Stationen, Beitr. Phys. fr. At., Bd. Huzi, Jn. Met. Soc. Jap., vol. 10, no. 6, 1932. 21, 105-118, 1934. pp. p. (360). W., Aeorologie der wandern- PEPPLER, Zur SCHEDLER, A., Die Beziehungen zwischen den Antizyldonen und Hochdruckrucken. Druck und Temperatur in der freien At- Beitr. Phys. d. fr. Atmos., Bd. 21, 93- pp. mosphdre, Beitr. zur Physik. der fr. At- 104, 1934. mosph., V. 9, pp. 181-201, 1920. (Earlier PEPPLER, W., Zur Aerologie des Fohns, study, id., v. 7, 1917, p. 88-102.) Beitr. z. Phys. d. fr. Atm., Bd. 12, pp. 198- SCHEDLER, A., Die Zirkulation im Nordat- 214, 1926. lantischen Ozean und den anliegenden Teilen PEPPLER, W., Zur Frage des Temperaturun- der Kontinente, dargestellt durch Hdufig- terschiedes zwischen den Berggipfeln und keitswerte der Zyklonen. Ann. d. Hyd., Bd. der freien Atmosphdre, Beitr. Phys. fr. At., 52, H. 1, 1924, pp. 1-14. Bd. 17, pp. 247-263, 1931. SCHERHAG, R., Aufbau, Zerstorung und starker PEPPLER, W., Der Zusammenhang Auswirkung einer der stdrksten iiber Deut- Druckdnderungen Temperatur- und am Boden schland gelegenen Frontalzonen, Ann. d. mit den hoheren Luftschichten iiber dem Al- Hydr., 1936, H. 11, pp. 491-492. penvorland, Beit. Phys. fr. At., Bd. 16, H. 1, zur Diver- pp. 1-8, 1929. SCHERHAG, R., Bermerkungen genztheorie, M. Z., v. 53, March 1936, pp. POGADE, G., Absterbende Warmsektorzyklo- 84 ff. nen, Ann. d. Hydr., 1938, H. 7, pp. 343-346. Theorie der Hoch- und (abstr. BAMS, 1939, p. 356). SCHERHAG, R., Zur Tiefdruckgebiete: Die Bedeutung der Diver- zur Kenntnis der Tro- PORTIG, W. Beitrdge genz in Druckfelder, M. Z., Bd. 51, pp. 129- Beitr. fr. At., Bd. 23, H. 2, popause, Phys. 138, 1934. pp. 121-128, 1936. SCHERHAG, R., Der Einflu^s starker tro- PORTIG, W., Gleichzeitige Temperatur- und posphdrischer Temperaturschwankungen auf Luftdruckdnderungen in der freien Atmos- den Luftdruck. Nach einer statischen Bear- phdre, Beitr. Phys. fr. At., Bd. 23, H. 2, pp. beitung der hollcindischen aerologischen Flug- 85-94, 1936. zeugaufstiege, Ann. d. Hydr., 1933, H. 10, 'QUAYLE, E. T., Relation between cirrus di- pp. 290-293. the rections as observed in Melbourne and SCHERHAG, R., iiber die atmosphdrischen •approach of the various storm systems af- Znstdnde bei Gewittern, Dissertation, Fr.- fecting Victoria. Australia, Comm. Bur. Wilhelms-Univ. Berlin, 1931, 93 pp. Met., Bull. no. 10, 1915, 27 pp. SCHERHAG, R., Warum gibt es in der Hohe und Grenzfldchen in RAETH.JEN, P., Fronten koine Fronten?, Ann. d. Hydr., 1937, H. 8, Ann. d. Hydr., 1938, Theorie und Erfahrung, pp. 367-368. H. 3, pp. 97-103. SCHMAUSS, A., Druckanstiege aus der 'kqua- RAO, J. Krishna, Distribution of temperature torialfront, Deutsches Met. Jrb. Bayern, India Met. Dept. in the lower stratosphere, 1922, Anhang E, 6 pp. Sci., Notes, V. 1, no. 10, 1930. SCHMAUSS, A., Lebensdaten der Mitteleuro- REED, W. G., The cyclonic distribution of paeische Depressionen, Deut. Met. Jahrbuch S., v. 39, 1911, p. rainfall in the U. MWR, f. Bayern, 1923, Anh. B and E, 1924, Anh. 1609-15. A. Vertikal- PEHORN, F. K., Kompensation aus SCHMAUSS, A., Polarfront-AQuatorialfront, Advektion? ("Wetter- bewcgung rder aus M. Z., Bd. 38, pp. 156-57, 1921. dynamik" Nr. 4), Beitr. z. Phys. d. Atm., A., Kohdrente und inkohdrente Bd. 25. pp. 189-219. 1939. SCHMAUSS, Drucksystemc, MZ, Bd. 39, pp. 278-280, 1922. L. F., and D. Proctor, Diffu- mCHARDSON, Temperature Wellen an der sion over distances ranging from 3 km to SCHMAUSS, A., Troposphdre und stratosphere. 86 km, Roy- Met. Soc, Memoirs, v. 1, no. 1, Grenze von Aerol. Stud. no. 1, Beob. an Met. pp. 1-8. 1926. Munch. Stat, in Kon. Bayern, v. 34, 1012, Append. HODEWALD. M., Frontenstun den und Fron- E. G. : further studies, id., Jg. 1913, App. 1936, H. 7. tenlagen, Ann. d. Hydr., pp. 1914; App. E and G, 1920, App. B. (See 314-316 ; further, 1936, H. 10, pp. 448-450. abstr. in Beitr. Phys. fr. Atmos., v. 6, pp. P,ODEWALD, M., Zur Frage der Zyklonenver- 153-172). der Kontinente, Ann. jiivaung am Ostrande SCHMIEDEL, K., Stratosphdrische Steuerung d. Hydr., 1937, H. 1, pp. 41-43. und Wellensteuerungen, Veroff. Geoph. "ROSSBY, C.-G.. Meteorologiska resultat av en Instit. Univ. Leipzig. Bd. 9, pp. 1-103, 1937. sommarseglats rundt de Brittiska Oearna, SCHMIDT, Wm., Hdufigkeitsverteilung des Medd. fran Statens Met.-Hydr. Anst., v. 3, vertikalen Temperaturqradienten. Beitr. z. no. 1. 16 pp., 1925. Phys. d. fr. Atm., Bd. 7. pp. 51-76, 1917. POSSBY, C.-G., Planetary flow patterns in SCHMITT, W., Fohnerscheinungen und Fohn- the atmosphere, QJRMS, v. 66, Supplement, gebiete mit einer Karte 1 .-80,000,000 29 Dia- pp. 68-87, 1940. grammen und Abbildungen, Deutsch. und Alpenvereins, Wissens- PUNGE. H., Zur Frage der Umwandlung besterreichisehen 64 einer kalten Antizyklone in cine wirme, M. chaftliche Veroffentlichungen, No. 8, pp., Z., Bd., 48, pp. 375-382, 1931. (abstr. of: 1930. )

BIBLIOGRAPHY 199

SCHOSTAKOWISTCH, W. B.. Die Beziehun- TRAVNICEK, F., Zur Kenntnis der Quellge- gen der Klimaelemente zueinander, Irkutsk, biete atmosphdrischer Unruhe, Ann. d. Hyd Mag. und Met. Obs., Verhandlungen, No. 4, H. 3, 1936, pp. 100-107. (Distrib. of inter- pp. 58-62, 1929. diurnal pressure variability, bibliog. SCHOSTAKOWITSCH, W. B., iJber die Ents- TSUTSUI, T. and C. Tsuboi, On the correla- tehung der Zyklonen, Irkutsk, Mag. und tion between the weather and the trend of Met. Obs., Verhandlungen, No. 4, pp. 12-16, upper isobars, Tokyo, Univ., Faculty of 1929. Sci., J., Sect. 1, V. 1, pt. 10, pp. 381-390, SCHOSTAKOWITSCH, W. B., ijber die Peri- 1927. odizitdt im Verlauf der Klimaelemente, Uber UDDEN, A. D., A Statistical study of surface die Kdlte-und Wdrmewellen und andere and upper-air conditions in cyclones and verwandte Erscheinungen, Irkutsk, Mag. und anticyclones passing over Davenport, Iowa, Met. Obs., Verhandlungen, No. 25- 4, pp. MWR, V. 51, 1923, pp. 55-68. 28, 1929. UYEDA, R. and others. Notes on correlations SEIFERT, G., Die Bedeutung wandernder pri- between the upper wind and the meteorolog- marer Drucksteiggebiete fiir Labilisierung ical elements, Tokyo, Univ., Faculty of Sci., und Zyklonenbildung, MZ, Bd. 52, pp. 429- J., Sect. 1, V. 3, pt. 2, pp. 107-147, 1935. 433, 1935. VANGENHEIM, G. J., To the Question H., Die rdumliche of SEILKOPF, und Zeitliche typi»ation and schematisation atmospheric Aufeinanderfolqe von Regenschauern, Ann. of processes, Moscow, Met. and Hydrol., 1938, d. Hydr., 58, H. 1-10, 1930. 1, pp. no. 3, pp. 38-58. SOLOT, S. B., The nature orographic Rain, of VENTURELLI, L., Contatti di masse d'aria BAMS, Oct., 1938, 348-9. pp. calda e d'aria fredda neW atmosfera in rela- SPILHAUS, A. F., A detailed study of the zione alia situazione barica, Venice, R. Inst. surface layers of the ocean in the neighbor- Ven., Atti, v. 93, pt. 2, pp. 731-867, 1934. hood of the Gulf Stream with the aid of (Abstr. in MZ, 1934, pp. 397-401.) rapid measuring hydrographic instruments, WAGEMANN, H., iJber Steiggebiete des Luft- J. Marine v. 3, no. of Research, 1, pp. SI- druckes bei russischen Kdltewellen (Ein TS, 1940. Beitrag zur Erkldrung der Luftdruck- STAUDE, R., Sind Schrximpfungsinversionen schwankungen am Boden). Berlin, Preuss. an Luftmassen oder Luftmassengrenzen ge- Met. Inst., Abhandlunsen. Bd. 9, no. 2, pp. bunden?, Ann. d. Hydrog., 1938, pp. 133-34. 5-62, 1929. (Abstr; MZ, v. 47, p. 475-81.) STONE, R. CMicrobarometric— oscillations at WAGEMANN, H., Die Wanderungsgesch- Blue Hill: Part 2 H. Helm Clayton's sta- windigkeit einer Depressionen ; vber Ener- tistical study of wave-like pressure oscilla- gieumsatz und Bildung der Sturmdepressio- tions observed at Blue Hill between 1885 nen, VerofF. Marineobs. Willemshavn, N. F., and 1893, BAMS, v. 16, pp. 158-159, 1935. Heft 2, 1936, pp. 9-39. STiJVE, G., Zur Frage der 'kquatorialfront, WEGENER, A., iJber die Rolle der Inversionen M. Z., Bd. 41, pp. 206-207, 1924. Der Zusam- in den Zyklonen, Ergeb. d. Lindenberg. menbang zwischen der oberen und unteren Tagung, Sonderband d. Beitr. z. Phys. fr. Druckwelle, Beitr. Phys. fr. Atmos., v. 13, At., 1921, pp. 47-51. no. 1. WEXLER, 'H.., Deflections produced in a trop- SVERDRUP, H. U., Ausgedehnte Inversions- ical current by its flow over a polar wedge, schichten in der freien Atmosphdre, Leipzig, BAMS, V. 16, pp. 250-252, 1935. Univ.. Geophs. Inst., 2. Serie, Spezialarbei- WIESE, Bruno, Sind die Uberadiabatischen ten. Heft 3, pp. 75-100, 1914. Gradienten Reell?, Dissertation, Leipzig SWOBODA, G., Grundbegriffe der Wetter- Univ., 1915. 40 pp. analyse, Prag, 1932, 48 pp. YANG, Chien-chu, The rise and fall of tem- THOMAS, H., Zum Mechanismsus stratosphd- perature and pressure over Mt. Taishan, risch bedingter Druckdnderungen, M. Z., Bd. (Abstract in Eng. ), Met. Mag. (China), v. 52, pp. 41-48. 1935. 13, No. 4, p. 255, April, 1937. THOMAS, M., [Radiosonde ascents in depres- ZIERL. H., Grosse Temperaturschwankungen sions in St. Paul. Amsterdamm Crozet, and im bayerischen Alpenvorland. Deutsches Met. Kerguelen Is.^. BAMS, v. 20, 1939, p. 323. Jrb., Bayern, 1923, Anhang G, 22 pp. v. and p. 359 ; C. Rend. Acad. Sci., Paris, ZISTLER, P., fiber die Zusammenhdnge zwis- 208, 1939, pp. 1419-20. chen troposphdrischen und stratosphdrischen THORNTHWAITE, C. W., The life history of Druckwellen, M. Z., Bd. 52, pp. 424-429, rainstorms, Geogr. Rev., v. 27, no. 1, 1937. 1935.

3. Air Mass Properties and Correlations

ALISOV, B. P., Dynamico-climatical analysis BANNON, J., Higgs, A. J., Martyn, D. F., as an addition to the problems of local cli- and Munro, G. H., The Association of me- matology, J. Geophys., vol. 6, no. 1, 1936, teorological changes with variations of ioni- pp. 33-49. zation in the F region of the ionosphere, Roy. Soc. London, Proc, A, v. 174, pp. 298- ALISOV, P., Geographical types of the cli- 309, Feb., 1940. mates. Moscow, Met. Hydrol., 1936, no. 6, pp. 16-25. BISOV, N. P., About the problem of applying the sounding of temperature for the char- ALISOV, B. P., Peculiarities of the meteoro- acteristics of weather types. Jn. of Geophys., logical regime of the summer of 1936 in V. 6. no. 1 (19), pp. 107-108 (summary in the central riart of the USSR. Moscow, Met. English), 1936. Hydrol., 1936, no. 12, pp. 3-17. BAKALOW, D.. Tiber die Transformation der ARAKAWA, H.. The air masses of Japan, Luftmassen, Beitrage z. Phys. fr. At., v. 26, BAMS, V. 18, pp. 407-410. 1937. h. 1, pp. 1-23, 1939. ASKNASY, A., The Cloudiness in Kislovodsk BLAKE, D., Further conclusions from addi- and mountain Sedlovaya in different tro- tional observations in the free air over San posnheric air masses (English summ.), Jn. Dieqo, Calif., M. W. R., v. 62, pp. 195-199, of Geophysics, v. 4, no. 3, 1934, pp. 311-331. 1934. 200 AIR MASS ANALYSIS

HESSELBERG, Th., and A. Friedmann, Die BLAKE, D., Temperature inversions at San Grossenordnung der meteorologischen Ele- Diego, as deduced from aerographical ob- mente und ihrer rdumlichen und zeitlichen servations by airplane, M. W. R., v. 56, pp. Ableitungen, Veroff. Geophys. Inst. Univ. 221-224, 1928. Leipzig, 2nd Ser., Bd. 1, H. 6, 1914, pp. BOTTS, A. K., Time-line cross-sections: Ap- 148-173. plication of a method of analyzing climatic lAROSLAVTZEV, I. M., Typhomologen der data by air masses, BAMS, v. 18, pp. 290- Hauptluftmassenarten iiber Zentralrussland, 297, ly37. Moscow, Met. Hydr., 1936, no. 7, pp. 26-42. BRAZELL, J. H. The relation between blue- JAW, J., Zur Thermodynamik der Passat- ness of the sky and (A) the polarity of the Grundstromung, Veroff., Met. Inst. Univ., air and (B) the gradient wind. Met. Off. Berlin, Bd. 2, H. 6, 1937, 24 p. Lond., Prof. Notes no. 85, 1938. JEOU-JANG, J., A preliminary analysis of DINES, L. H. G., Lapse rates in polar and the air masses over eastern China, Memoir equatorial air. Met. Mag., Jan. 1929, p. Nat. Res. Inst. Met., China, no. 6, 24 pp., 285-6. 1935. CHROMOV, S. P., vber die dynamische Kli- KALININ, N. F., Characteristical curves of matologie der Krim, J. Geophysics, v. 5, no. Rossby for certain air masses in Minor Asia, 1, pp. 156-159, 1935. Moscow, Met. Hydrol., 1938, no. 3, pp. 35-39. P. E., Dynamic climatology, BAMS, CHURCH, KEIL, K., and W. Kopp, Vsber die Bezeich- V. 15, pp. 128, 1934. nung der Luftkorper, Mitt. d. preuss. Aeron. DEJORDJIO, v., and A. Bugaev, On the air Obs. Lindenberg, 1927, pp. 109-111 mass classification in Middle Asia, Moscow, KIMBALL, H. H., Turbidity and water-vapor Met. Hydr., no. 6, pp. 72 ff, 1936. determinations from solar radiation meas- DINIES, E., Luftkorper-Klimatologie, Aus urements at Blue Hill and relations to air- Bd. dem Archiv der deutschen Seewarte, 50, mess types, M. W. R., v. 62, pp. 330-333, nr. 6, 21 pp., 1932. 1934. DROZDOV, M. P., Conditions of the summer KNOCH, K., Polar- und Tropikluft nach transformation on the air masses in the Registrierungen der Temperatur und der Moscow region, Moscow, Met. Hydro!., 1936, relativen Feuchtigkeit auf dem Atlantischen no. 5, pp. 36-40. Ozcan, M. Z., Bd. 42, pp. 297-302, 1925. graphical EARL, K., and T. A. Turner, A LANDSBERG, H., The air mass climate of Inst, means of identifying air masses, Mass. central Penna., Gerl. Beitr. z. Geophys. Bd. No. 4, 1930, Tech. Met. Course, Prof. Notes, 51, pp. 278-85, 1937. [Abstract in BAMS, v. out of print. 19, pp. 30-33, 1937.] EGERSDORFER, H., Fragen der praktischen LAPAYRE, Mesure an avion de I'humidite at- Aerologie, M. Z., Bd. 54, pp. 483-485, 1937. mospherique en altitude a Djibouti, Annal. EVSEEV, P. K., The course of meteorological de Phys. du Globe, No. 33, 1939, p. 92. through elements with passing of fronts LINKE, F,, Achtjahrige Luftkorperbestim- Moscow during the summer months, Moscow, mungen in Deutschland, Bioklimat. Beiblat- no. 4-5, 28-47. Met. Hydrol., 1937, pp. ter, Jg. 4, pp. 101-106, 1937. the anti- FEDEROV, E. E., Weather types at LINKE, F., Luftmassen oder Luftkorper? the European cyclones in the steppe track of Bioklim. Beiblatter, Bd. 3, pp. 97-103, 1936. part of USSR in the summer half-year. Bull. D. H. and Paul Cast, Air Acad. d. Sci. URSS, CI. Sci. Math. Nat., LOUGHRIDGE, intensity. Bull. Ser. Geogr. et Geophys., v. 1937, no. 1, p. mass effect on cosmic-ray no. 7 ff, 1940. 147-8. Am. Phys. Soc, v. 14, 6, pp. FONTELL, N., Zur Frage der inneren Stabili- MOESE, O., and G. Schinze, Die Erkennung tdt der Luft-inassen verschiedenen TJrs- der troposparischen Luftmassen au^ ihren prungs. Mitt, des Met. Inst, der Univ., Hel- Einselfeldern, M. Z., Bd. 49, pp. 169-179, aingfors, no. 22, pp. 1-20, 1932. 1932. GEIGER, R., iiber die Entwicklung von Luft- M6LLER, F., Statistische Untersuchungen korperwetterlagen und iiber Luftkorperfol- iiber die Konstanz der Luftkorper, Gerl. gen in Munchen, Zeit. f. angew. Met., Das Beit. Geophys., Bd. 37, pp. 387-435, 1929. Wetter, Jg. 49, pp. 359-370, 1932. NISHINA, Y., H. Arakawa, et al.. Commie GERLACH, A. C, Distribution of air-mass rays as a possible meteorological factor, J- types and frequency of change in the west- Met. Soc, Japan, v. 18, no. 5, p. 160-163, R., ern United States driving 19S7-3S, M. W. no. 8. pp. 256-60. [Abstr. in Eng. on pp. V. 66, pp. 376-377, 1938. (17-18) ], 1940. A. H. R., Characteristics of rainfall GOLDIE, PICK, W. H. and Davies, Ground horizontal distribution in homogeneous air currents visibility at Valentia and the type of air and at surfaces of discontinuity. Met. Off., prevailing, QJRMS, v. 55, 1929, p. 81-2 ; London, Geophys. Mem., No. 53, 1931, 19 see also, v. 53, p. 293. pp. GOLDIE, A. H. R., Rainfall at fronts of de- POLIAKOVA, A. N., The Distribution of pression, London, Met. Off., Geophysical equivalent-potential temperature in tro- Memoirs, No. 69, 17 pp., 1936. pospheric air masses over Moscow, Jn. of Geophysics, vol. 6, No. 6 (24), pp. 524-525 H., und K. BiJRGER, Bin GOLDSCHMIDT, in English), 1936. Beitrag zur Abhdngigkeit des luftelektrischen (summary Potentialgefdlles vom, Lnftkorper, M. Z., Bd. POULTER, R. M., Configuration, air mass 51, pp. 286-289, 1934. and rainfall, QJRMS, v. 62, pp. 49-80, 1936. GRITZENKO, M. V., and A. F. Dubuk, Com- RODEWALD, M., ijber die Festlegung von plete energy reserve of air-mass instability Frontalzonen, Annal. der Hydrog., Bd. 60, over Moskow, Moscow, Met. Hydr., 1939, no. h. 5, pp. 180-183, 1932. [Position of polar 5, pp. 29-43. front in No. America.] HAURWITZ, B., Day time radiation at Blue Hill Observatory in 1933 with application RODEWALD, M., Zum Artwandel der Luft- to turbidity in American air masses. Har- massen, Ann. d. Hydrog. Bd. 65, pp. 583- vard Met. Studies, no. 1, 1934, 31 pp. 1937. BIBLIOGRAPHY 201

SCHELL, I. I., On the diurnal variation of TROEGER, H., Die Aequatoriale Luftmasse, wind, Gerl. Beitr. Geophys., Bd. 47, pp. 60- Annal. d. Hydrog., Bd. 65, H. 11, 1937. pp. 72, 1936. 525-526. SCHINZE, G., Troposphdrische Luftmassen TSCHIERSKE, H., Geographische Grenzen der und vertikaler Temperaturgradient, Beitr. z. Luftmassen Europas im Jahresgang der Phys. d. fr. Atm., Bd. 19, pp. 79-90, 1932. Verlagerung, Mitt. Ver. der Geographen SCHULZ, L., lonenspektrum und Luftkorper Univ. Leipzig, Heft 14/15, 1936. verschiedenen Orten, nach Messungen an TU, Chang-Wang, The air masses of China, Frankfurt, Wetterdienststelle, Synoptische Memoir Nat. Res. Inst. Met., China, v. 12, 19-22, Bearbeitungen, Linke Sonderheft, pp. no. 2, 50 pp., 1938. 1933. TU, C.-W., Chinese air mass properties, SCHWANDKE, F., Die innere Beibung der QJRMS, V. 65, pp. 33-51, 1939. Atmosphdre in Abhdngigkeit von der Luft- masse, M. Z., Bd. 53, pp. 396-397, 1936 VOIGTS, Heinrich, Zum Luftkorperklima der Lilbecker Bucht, MZ, Bd. SERRA, A., and L. Ratisbonna, Air Masses of 50, pp. 498-503, 1933. southern Brazil, M. W. R., v. 66, pp. 6-8, 1938. WEGER N., Luftkorper und Grossenvertei- SHOSTAKOWITSCH, W. B., Herkunft der lung der atmospharischen lonen, Gerl. Beitr. Niederschlag (Zur Klimatologie der Luftkor- Geophys, Bd. 42, Hf. 2/3, 1934. (Diss. per), Mem. Inst. Hydro!., Leningrad, v. 14, Frankfort, 1934.) 1935, p. 35 ff. WILLETT, H. C, American air mass prop- SHOWALTER, A. K., Further studies of erties. Papers in Physical Oceanography American air-mass properties, M. W. R., v. and Meteorology, Mass. Inst, of Tech. and 67, pp. 203-217, 1939. Woods Hole Oceanogr. Inst., Vol. II, No. 2, 116 pp., 1933, out of print. Abstr., Jn., STONE, R. G., On some possibilities and limi- Aeron. ScL, Apr., 1934. (Abstr. in Appen- tations air mass climatology , Annals of of dix the Assoc. Amer. Geographers, March, 1935. to this booklet.) [See ad. by Showaiter, (abstr.) MWR, V. 67, p. 203-17, 1939.] STONE, R. G., A modern classification of WEXLER, H., A comparison of the Linke and weather tyi:>es for synoptic purposes, BAMS, Angstrom measures of atmospheric turbidity V. 16, pp. 324-326, 1935. and their application to North American air masses, Amer. Geophys. Un., Trans., STUMMER, G., Unterschiede in der Luftkor- 14th ann. meet., 1933, pp. 91-99. perhdufigkeit von Miinchen und der Zug- spitze, Bioklima. Beiblatter, Jg. 4, pp. 97- WEXLER, H., Cooling in the lower atmos- 100, 1937. phere and the structure of polar continental air. M. R., TAKAHASHI, K., Dynamic climatological con- W. v. 64, pp. 122-135, 1936. sideration on the alternation of weather in WILLETT, H. C, Ground plan of a dynamic early winter in the Far East, J. Met. Soc. climatology, M. W. R., v. 59, pp. 219-223, Japan, v. IS, pp. 177-190, 1940. 1931. E. SPECIAL AIDS TO ANALYSIS AND FORECASTING 1. Charts, Rules, Techniques, Thermodynamics, Formulae, Nomograms ALLEN, C. C, Minimum tew.perature fore- BAUER, L. H., Die Beziehuvgen zwischen po- casting in the Central California citrus dis- tentieller Temperatur und Entropie, M. Z., trict, M. W. R., V. 67, pp. 286-294, 1939. Bd. 25, pp. 79-82, 1908. (In English, Phys. ALVORD, C. M., and R. H. Smith, The tephi- Rev., 1908) gram—its theory and practical use in BAUR, F., Die interdiurne Verdnderlichkeit weather forecasting, M. W. R., v. 57, pp. des Luftdrucks als Hilfsmittel der indirek- 361-369. 1929. ten Aerologie, Synoptische Bearbeitungen, ARAKAWA, H., Energy realisable in the un^ Wetterdienststelle Frankfurt, no. 4, pp. 21- stable atmosphere, Geophys. Mag., Tokyo, v. 28, 1933. 12, no. 1, 2, pp. 8-13, 1938. BAUR, F., The significance of the strato- ARAKAWA, H., A new type of Rossby Dia- sphere for the broad-weather situation, gram, BAMS, V. 21, p. 111. 1940. BAMS, V. 18, pp. 378-80, 1937. ARAKAWA, H., Thunderstorm forecasting BERG, H., Nomogramme zur Ermittlung des with the aid of charts representing the to- Gradientwindes aus Karten der Topographic pography of condensation level, J. Met. Soc. bestimmter Isobarenfldchen, Erfahrungsbe- Japan, 1939, pp. 101-103. (Abstract in richte des deutsch. Flugwetterdienstes, 8. English, pp. 10-11). Folge, Nr. 18 bis 21, pp. 153-155, Marz, AUJESZKY, L., iJber die Benutzung der Aquiv- 1934. alenttemperatur in der wetterdienstlichen BERGERON, Tor, Hydrometeorbeschreibungen Praxis, Gerl. Beitr. Geophys., Bd. 34, pp. mit den vom internationalen meteorologis- 131-141, 1931. chen Kommittee in Salzburg 1937 angenom,- AUJESZKY, L., Zur praktischen Differential- menen Anderungen, ( Text in German, French diagnose der hohen und niedrigen Druckten- and English), Sweden, Statens met.-hydro. denzerschcinungen auf der Wetterkarte, Anstalt, Communications, Series of papers Ann. der Hydrog., Bd. 43, pp. 430-432, 1935. no. 22, 1939. [The new Int. code for hydro- meters] FUJIWHARA, S., Pressure maps at three kilometers in Japan, M. W. R., v. 49, pp. BERGERON, T., On a manual of weather 571-572, 1921. map analysis, Un. Geod. et Geophys. Intern. Sept., 1936, BALLARD, J. C, Table for facilitating com- 6ieme Ass. Gen., Edimbourgh, Met., part 2, putation of potential temperature, M. W. Proces verbaux de I'Ass. de Disc, 266-272. R., V. 59, pp. 199-200, 1931. Mem. et pp. BANERJI, S. K., Microseisms associated with BILANCINI, R., Sul metodo delle variazioni, disturbed weather in the Indian Seas, Roy. le correnti regolari di perturbazione, Rivista Soc. Lond., Philos. Trans., Series A, v. 229, di meteorologia aeronautica, An. 1, no. 2, pp. 287-328, 1930. pp. 1-18, 1937. )

202 AIR MASS ANALYSIS

BJERKNES, v., Wettervorhersage. Zeit. f. DOUGLAS, C. K. M., A further note on "The Phys., Bd. 23. pp. 481-490, 1922. application of wet-bulb potential temperature to air analysis" v. BLEEKER, W., Beitrag zum Definition von mass , QJRMS, 64, Aequivalentund reuchttemperaturen, M. Z., no. 273, pp. 122-123, 1938. Bd. 57, pp. 111-115, 1940. DUFOUR, L., Notes sur le probleme de la ge~ BLEEKER, W., A diagram for obtaining in lee nocturne, Belgium, Inst. Roy. Met., Me- a simple manner different humidity elements moires, v. 9. 24 p., 1938. and its use in daily synoptic work, BAMS, DYKE, R. A., Upper winds as related to the V. 20, pp. 325-329, 1939. moveme?it of tropical disturbances over the BLEEKER, W., On the conservatism of the Gulf of Mexico, BAMS, v. 20, pp. 281-282, equivalent potential and the wet-bulb po- 1939. tential temperatures. QJRMS, v. 65, Oct. EKHOLM, N., Wetterkarten der Luftdruck-

1939, pp. 542-550. schwankungen, MZ, v. 21, 1904, pp. 845-357 ; BOEREMA, J.,Daily forecast of windforce on further, MZ, 1906, p. 228, 1907, p. 1, 102, Java, Kon. Mag. en Met. Obs. Batavia, Ver- and 145. hand. no. 27, 1934, 8 p. ELLISON, E. S., A critique on the construc- BOWIE, E. H. and R. H. Weightman, Types tion and use of minimum-temperature for- of Storms of the U. S. and their average mulas, M. W. R., v. 56, pp. 485-495, 1928. movements, MWR Suppl. 1, 1914 ; Types of FJELDSTAD, J. E., Graphische Methoden zur Anticyclones , MWR Suppl. no. 4, Ermittelung adiabatischer zustandsdnderun- 1917. gen feuchter Luft, Geofys. Pub,, v. 3, no. 13, BROWN, C. v., A design for a geostrophic pp. 3-25. 1925. wind scale, BAMS, v. 21, pp. 178-181, 1940. FRIEND. A. W.. Developments in Meteorolog- BRUNT, D., The adiabatic lapse-rate for dry ical Sounding by Radio Waves, J. Aero. Sci., and saturated air, QJRMS, v. 59, 1933, p. V. 7, 1940, pp. 347-352. (Abstr., BAMS, v. 351-60; (see also his "Physical and Dynam- 20, 1939, p. 202-5.) [troposphere discontin- ical Meteorology." uities] BUREAU, R., Centres of thunderstorms and FUJIWHARA, S. and Z. Kanagawa, On the "centres" or sources of atmospherics, barometric oscillation with period more than QJRMS, V. 64, pp. 331-335', 1938. 10 minutes and its use in weather forecasting, Geophys. Mag., Tokyo, v. 1, no. 6, H. R., On the thermodynamic inter- BYERS, 1928. pretation of isentropic charts, M. W. R., v. 66, pp. 63-67, 1938. GILKESON, W. R., The use of weather forecasts in electric power system operation, BYERS, H. R., The meteorological phase of BAMS, V. 20, pp. 338-340, 1939. flood-forecasting. Trans. Amer. Geophys. Union, 1939, Part 2, pp. 205-207. GOLD, E., Aids to forecasting : types of pressure distribution, with notes and tables- H. R., The use of free-air soundings BYERS, for the fourteen years 1905-191S. London, in general forecasting, MWR, v. 62, pp. 376- Met. Off., Geophys. Mem., no. 16, pp. 179- 378, 1934. 200, 1925. (Add. by Pick, QJRMS, v. 55, BYSOV, N. P., Some remarks to the question p. 403, 1929.) of using the baric topographical charts in GOLD, E., day temperatures synoptic practice, Moscow, Met. HydroL, Maximum and the tephigram, London, Met. Office, Prof. 1939. no. 3, p. 28. Notes, no. 63 (v. 5), pp. 3-9, 1933. CANNEGIETER, H. G. und Bleeker, W., TabeUen Zur Ermittlung von Druckwerten in GREGG, W. R., and I. R. Tannehill, Interna- geodynamischen Stufen aus denen in geo- tional standard projections for meteorological charts, M. R., v. 411-414, metrischen Hohen und umgekehrt, Beitr. W. 65, pp. 1937. (See also: Comm. on Proj. Met. Phys. fr. At., Bd. 24, pp. 18-25, 1938. Charts, 1937, Secret. Org. Met. Int., Pub. DAY, J. A., Aviation wind forecasts over the No. 39, 1939.) Pacific. BAMS, v. 20, pp. 340-345, 1939. GROSSMAN, Wie steht es um unsere Wetter- DEUTSCHE FLUGWETTERDIENST, Berlin. vorhersage? Ann. d. Hydrog., 1912, pp. 1-23. Erfahrungsberichte. Neudruche (reprint) GUILBERT, G., La prevision scientifique du vols. 1-4 ; Berlin, 1937-8. [These reports contain many brief articles on details of air- temps. Traite pratique. Paris, Augustin ways weather analysis and services, instru- Challamel, 1922, 439 pp. (2nd. ed.) ments, reduction of aerological observations, HARTMANN, W., Die Ermittelung der Verti- etc., helpful for students and airway mete- kalbewegung aus der Stromung, deutsch. orologists even outside of Germany.] Flugwetterdienstes, Erfahrungsberichte, Folge- DIESING, K., Graphische Ermittlung von 9, Nr. 26, pp. 159-163, Mai 1936. Aquivalenttemperaturen und spezifischer HARTUNG, K., Die Wiedergabe periodischer Feuehte. Ann. der Hydrog., Bd. 39. pp. 381- Druckschwankungen auf gemittelten Isallo- 382, 1931. barenkarten, Ann. d. Hydr., 1935, H. 11, pp. 421-429. DINIES, E., Untersuchungen des Referats PrognosenbeurteilUng in der Synoptischen HAURWITZ, B., and J. R. H. Noble, Maps of Abteilung des Reichsamts fUr Wetterdienst, the pressure distribution in the middle tro- Deutsch. Flugwetterdienstes, Erfahrungsbe- posphere applied to polar anticyclones, richte, Sonderband 5, Teil 1 und 2, pp. BAMS, V. 19, pp. 107-111, 1938. Corr., id.,,

1/1-1/2 ; and ix/l-x/4 with weather maps, p. 272. 1936. HAYNES, B. C., Upper-wind forecasting, DINIES, E., Zur methodik der Wettervorher- M. W. R., V. 64, pp. 4-5, 1938. sage, Ann. d. Hyd., v. 548-51. 66, 1938, pp. HEIDKE, P., ijber periodische und unperio- DOPORTO. M., Tipos de distribucion isobdrica dische Luftdruckschwankungen sowie iiber y de tiempo en el Golfo de Vizcaya. 1. In- tropische synchrone Luftdruckkarten. Gerl. troduccion y generalidades. San Sebastian, Beitr. Geophys., Bd. 34, pp. 186-218, 1931. Obs. de Igueldo, Trab. Publ. 4.4. 1929, 40 HILAIRE, P., et J.-M. Pruvost, Bases de la pp. prevision a tres courte echeance au Ca/me- DOUGLAS, C. K. M.. Bergen daily charts. roun. Annales de Phys. du Globe, no. 31,. Met. Mag., v. 62. 1927. pp. 61-63. pp. 8-27, 1939. BIBLIOGRAPHY 20S

HOLTZMANN, M. J., Zur Frage des Genauig- MEISINGER, C. L., The preparation and sig- keitsgrades der Luittemperatur und Feucli- nificance of free-air 2^ressure maps for trie tigkeitsbesthnniungen in natiirlichen Ver- central and eastern United States, M. W. hdltnissen, M. Z., Bd. 53, pp. 327-336, 1936. R.. Suppl. no. 21, 77 p., 1922. INT. MET. ORGANIZATION and Deutsche MILLAR, F. G., Rapid methods of calculating Seewarte, Cartes synoptiques de I'hemisphere the Rossby diagram, BAMS, v. 17. pp. 176- nord, Aug. 1, 1932 to July 30, 1933. [Issued 180, 1936. in parts of 3 months each ; —the Polar year MIRRLEES, S. T. A., Climatology and fore- results] Hamburg, 1937. casting. Met. Mag., v. 74, no. 878, pp. 40- INTERNATIONALE METEOROLOGISCHE 44, 1939. ORGANIZATION, Internationale Aerolo- L., \ MITCHELL. C. Forecasts for a week in / gische Kommission, Mher Aerolcgische Dia- advance based on northern hemisphere des Praesiden- grammpapiere, Denkschrift weather maps, BAMS, v. 9, pp. 101-102. ten der Internationalen Aerologischen Kom- 1928. mission Prof. Dr L. Weickmann, Berlin, MONTGOMERY, R. B., Circulation in upper 1938, 2 Vols. [Thorough review; bibliog.] layers of southern North Atlantic deduced JACOBS, W. C., Applications of Brunt's ra- with use of isentropic analysis, Mass. Inst. diation equation to minimum-temperature of Tech. and Woods Hole Oceanographic 433-439 forecasting, M. W. R., v. 67, p. Inst.. Papers in Met. and Oceanogr., v. 6, 1939. no. 2, 49 pp.. 1938. KASTER, H. B., and Counts, R. C, Quantita- MONTGOMERY, R. B., A suggested method tive evaluation of fronts, BAMS, v. 21, 1940, of representing gradient flow in isentropic pp. 125-6. surfaces, BAMS, v. 18, pp. 10-12, 1937. KINKA, T., Some problems concerning storm M6LLER, F.. Pseudopotentielle und dquivalent- prediction for the Oosaka district, Jn. Met. potentielle Temperatur, M. Z„ v. 56, pp. Soc. Jap., V. 15, no. 9. p. (34)-(35) ; (also: 1-12, 1939.

On the prediction of rain for Osaka, id. ) ; NAMEKAWA, T., A study of minor fluctua- 2nd paper, id., v. 16, no. 5, 1938, p. (16). tions of the atmospheric pressure, Mem. KLENIM, I. A., Synoptical conditions of the Coll. Sci., Kyoto Imp. Univ., A, v. 18, no. flight and meteorological protection of the 2, 1935, pp. 83-127, and no. 4, pp. 173-200. North Pole Expedition, Moscow Met. Hydrol., NAMIAS, J., The forecasting significance of no. 6, pp. 23-41, 1937. anticyclonic eddies on the isentropic chart. KNOBLOCH, H., Nomogram zur Bestimmung Trans. Amer. Geophys. Union, 1938, pt. 1, der Aequivalenttemperatur, M. Z., Bd. 49, pp. 174-176. p. 318, 1932. NEWNHAM, E. V., Classification of synoptic KoNIG, W., Vsher die Erschliessung hoher charts for the North Atlantic for 1896-1910. Druckwellen durch Anderungskarten, Ber. London, Met. Off., Geophys. Mem., V. 3, no. Tat. d. Preuss. Met. Inst, fur d. Jr. 1927, 26, pp. 179-200, 1925. pp. 56-61. NICHOLS, E. S., Predicting minimum tem,- KRICK, I. P., Air mass symbols for use on perature, especially as a function of pre- synnqjtic charts, J. Aeron. Sci., v. 2, p. 55, ceding temperature, M. W. R.. v. 58. pp. 1935. 179-189, 1930.

KRICK, I. P., Forecasting problems in the NORMAND, C. W. B.. On instability from western United States, BAMS, v. 15, pp. water vapour, QJRMS, v. 64, no. 273, pp. 231-234, 1934. 47-170, 1938. (Reply to crit., id., p. 338-40.) LANSING, L., Weather preceding forest fires NORMAND. C. W. B., Wet bulb temperatures in New Hampshire, BAMS, Jan. 1939, pp. and the thermodynamics of the air, India 10-26 [bibliogr.]. Met. Dept.. Memoirs, v. 23, pt. 1, pp. 1-22, 1921. LARSON, O. T., The relationship between air- line dispatching and meteorology, with ref- OGASAHARA, K., Frontological studies on erence to the practice of the United Air the rain belt distributed along the skirt of Lines, BAMS, v. 18, pp. 331-335, 1937. the continental high in the low latitude LEE, A. W., Microseisms and weather. Met. West Pacific coasts, Taiwan, Formosa, J. Soc. Trop. Agric, v. 2, no. 3, 1939, pp. Mag., V. 73, 1939, pp. 317-324 ; A world-wide 258-268. survey of Microseism,ic Disturbances, Geo. phys. Mem., Met. Off., London, No. 62, PAGE, L. F., (ed. ), Reports on critical stud- 1934, 33 pp. ies of methods of long range weather forecasting, no. 1940. LEJAY, R. P. P., Etude des Atmospheriques M. W. R., Suppl. 39. 1932-1935, Zi-ka-wei, Obs., Notes de Meteoro- 130 p. logie Physique, Fasc. 4, 16 pp., 1935 (in PAGLIUCA, S., The problem of forecasting French). [Tracking storms] sleet for highway and industrial purposes. Trans. Am. Geophys. Union, 1937, pp. 551- LETZMANN. J., Zur Darstellung der dquiva- 554. (Bibliography of sleet and glaze.) lent-potentiellen Temperatur in Schnitten, Ann. der Hydrogr., Mar. 1938, pp. 109-115. PAGLIUCA, S., Some aspects of industrial weather forecasting, BAMS, v. 20, pp. 287- LICHTBLAU, S., A design for a geostrophic 293, 1939. wind-scale, M. W. R., v. 65, pp. 109-110. 1937. PEMBERTON, B. V., Weather forecasting in Techn., v. 2, LITTLE. D. M., and E. M. Vernon, Reduction New Zealand, N. Z. Jn. Sci. 165-179, 1919. of the barometric pressure over the plateau no. 2, no. 3, pp. 87-94, to the 5,000 foot level, M. W. R., v. 62, pp. PEPPLER, W., iJber Temperatur und Feuch- 149-155, 1934. tigkeit in der freien Atmosphdren an Gewit- At., Bd. LONDON, Met. Office. Computer's handbook, tertagen, Beitrage z. Phys. der fr. 1916 and 1921. 21, pp. 121-128, 19341 MEISINGER, C. L., Concerning the accuracy PETITJEAN, L., Le temps et la prevision du of free-air pressure maps, MWR. v. 51. 1923, temps en Algerie et en Sahara, Algeria, pp. 190-199. Service Met., Etudes Sci., 70 pp., Paris. 1930. 204 AIR MASS ANALYSIS

PIERCE, C. H., On the use of vertical cross raison synoptique des ondes de pression et sections in studying isentropic flow, M. W. de variation de pression, Beitr. z. Phys. d. R., V. 66, pp. 263-267, 1938. fr. Atmos., v. 14, pp. 111-118, 1928. POGADE, G., Vsber die interdiurne Verdnder- SCHERHAG, R., Die Entstehung der im lichkeit der Hohenschwankungen der einzel- "Tdglichen Wetterberich" der Deutschen nen Hauptisobarenfldchen, Ann. d. Hydr., Seewarte veroffentlichten Hohenwetterkarten 1939, H. 5, pp. 277-281. und deren Verwendung im Wetterdienst, M. PORTIG, W., Numerische Berechnung des Z., Bd. 53, pp. 1-6, 1936. straiosj^harischen Einflusses auf den Boden- SCHERHAG, R., Verbesserung der Wettervor- druck, Ann. d. Hydrog., 1936, H. 2, pp. 35- hersage durch Berechnung der Druckvertei- 36. lung des Folgetages mit Hilfe der Hohen- wetterkarte, Ann. d. Hydr., 1939, H. 9, pp. PRAMANIK, S. K., Upper air data and daily 462-465. weather forecasts, Proc. Nat. Inst. Sci. of India, v. 5, no. 1, pp. 123-128, 1939. SCHINZE, G., and R. Siegel, A large-scale upper-air stream chart, BAMS, v. 20, pp. RAETHJEN, P., Warum virtuell-feuchtpoten- 258-260, 1939 (Aus dem Archiv der d. See- tielle Temperatur in Vertikalschnitten?, warte, V. 58, no. 2, 1938). Criticism by R. M. Z., V. 56, pp. 263-265, 1939. SCHERHAG, Bull. Amer. Met. Soc, June praktischen Anwendung RAETHJEN, P., Zur 1939, pp. 260-262. (Ann. d. Hydrog., June, der Margidesschen Gleichgewichtsbedingung, 1939). M. Z., V. 56, pp. 58-62, 1939. SCHMIDT, G., Die Druckdnderungsgebiete der EAMDAS, L. A., The prediction of minimum 500 Mb-Fldche und ihre prognostische Ver- selected sta- temperature on clear days at wertung, MZ, Bd. 57, pp. 26-32, 1940. tions in India, Met. Mag., v. 73, pp. 237- SEILKOPF, H., Eindrilcke und meteorolo- 238, 1938. gische Erfahrungen auf der Weltfahrt des RAO, P. R. Krishna, Weather forecasting for Luftschiffs "Graf Zeppelin" , Hamburg, Mitt. reference to local fore- aviation with special Geog. Ges., v. 41, pp. 228-259, 1930. casts, Proc. Nat. Inst. Sci. of India, v. 5, H., Meteorologische Arbeiten zur no. 129-138, 1939. SEILKOPF, 1, pp. Vorbereitung und Sicherung des Ozeanluft- REFSDAL, A., Das Aerogratnm, Ein neues verkehrs. Probleme und Ergebnisse, M. Z., Aerologische Berech- Diagrammpapier fiir Bd. 51, pp. 1-0, 1934. nungen, M. Z., v. 52, no. 1, Jan., 1935, pp. SEILKOPF. H., Die Meteorologischen Pro- 1-5. Aerologisches Diagrampapier, Geof. bleme des Transatlantischen Luftverkehrs, Publ. Vol. 11, No. 13, 1937. Jarhbuch d. Wissenschaftlichen Gesellschaft F. Meteorological REICHELDERFER, W., fiir Luftfahrt, E. V., 5, pp., 1935-36. aspects airship ojieration, Daniel Guggen- of SEILKOFF, H., Ozean-flug und Hohenwetter- Airship Institute, Pub. No. 3. 1935, pp. heim dienst, Ann. der Hydrogr., Jan., 1938, pp. 97-103. 35-42. L. F., Weather prediction by RICHARDSON, SEKIGUCHI, R., High-level isobars as tised in process, Cambridge, 1922, 236 p. numerical everyday weather service, MWR, v. 50, 1922, ROBITZSCH, M., Die Verwertung der durch pp. 242-243. aerologische Versuche gewonnenen Feuch- SELLICK, N P., Weather maps and the short- tigkeitsdaten zur Diagnose der jeweiligen _ period forecast in Southern Rhodesia, Rhod. atmosphdrischen Zustdnde, Arbeiten d. pr. Sci. Assoc, Proc, v. 33, pp. 15 ff., 1934. Aeronaut. Obs. Lindenberg, Bd. 16, 1930, Puri, Air-mass anal- pp. C 1-28. SEN, S. N., and H. R. ysis and short period weather forecasting in M. Die Entstehungsbedingun- RODEWALD, India, Proc. Nat. Inst, of Sci. of India, v. gen der tropischen Orkane, M. Z., Bd. 53, 5, no. 1, pp. 75-92, 1939. pp. 197-211, 1936. SENGUPTA, S., Zur Verwendung von Pilot- M., Hohenwetterkarte und Wet- RODEWALD, balloonen im Wetterdienst, Berlin, Univ. tervorhersage, Ann. d. Hydrogr., Jan. 1938, Met. Inst., Veroffentl., Bd. 3, H. 5, 18 pp., 42-48. pp. 1939. M., Zur Weltwetterkarte, Annal. RODEWALD, P., iJber die theoretischen 1931. SMOLIAKOW, d. Hydrog., v. 59, p. 304, Grundlagen der Exner und Defantschen ROME, Ministero deH'Aeronautica, UfRcio Pre- Regeln, Moscow, J. Geophys., v. 3, no. 1, pp. sagi, Principali tipi isobarici interessanti 64-76, 1933. ritalia (quinquennio 1926-1930). Rome, 1931. 12 pp. SOHONI, V. v., and M. M. Paranjpe, Latent instability in the atmosphere revealed by Thermodynamics applied to ROSSBY, C.-G., some Indian tephigrams, India Met. Dept., air mass analysis, Mass. Inst, of Tech. Me- Memoirs, v. 26, pt. 7, pp. 131-149, 1937. teorological Papers, Vol. I, No. 3, 41 pp., 1932. SPILHAUS, A. F., Comment on Refsdal's the "Tephigram", BAMS, ROSSBY, C.-G., and Collaborators : Isentropic "Aerogram", and Analysis, BAMS, v. 18, pp. 201-209, 1937. V. 21, pp. 1-3, 1940. ROY, A. K., On the forecasting of rain over SPILHAUS, A. F., Contribution to the tech- South Bengal during the nor' wester season, nique of isentropic analysis, BAMS, v. 21, mid-March to mid-May, India Met. Dept., pp. 239-248, 1940. Scientific Notes, v. 8, No. 83, 8 pp., 1939. SPILHAUS, A. F., Hyperbolic dividers for RUDLOFF, W., Berechnung der Hohe einer geostrophic wind computations, BAMS, v. Fldche gleichen Druekes mit Hilfe des Sen- 19, pp. 351-353, 1938. krechten Temperaturgefdlles, Ann. d. Hydr., 1938, H. 6, pp. 302-304. SPILHAUS, A. F., Isentropic airplane flights suggestion, BAMS, v. 19, pp. 279-280, SCHELL, I. I., Chromov's rules for forecast- —a 1938. ing synoptic situations BAMS, v. 16, pp. 21-22, 71-73, 108-110, 1935. STARR, v.. The construction of isentropic SCHERESCHEWSKY. Ph., and Ph. Wherle, relative motion charts, BAMS, v. 21, pp. Sur la prevision barometrique par compa- 236-248, 1940. BIBLIOGRAPHY 205

STEVENS, W. R., Meteorological conditions Obs., pp. 165-168, 1928, [surface maps of preceding thunderstorms on the national equivalent, equiv.-pot., and pot. temp, com- forests. 1. Western and central Oregon, M. pared]. W. R., V. 62, pp. 366-375, 1934. U. S. WEATHER BUREAU. Numeral Weather STiJVE, G., Die Darstellung meteorologiseher Code, 1939. Deutsch. Elemente in Vertikalschnitten, U. S. WEATHER BUREAU, Distribution of Flugwetter dienstes. Erfahrungsberichte, weather information by radio, WB Radio 1-7, Juli, 1934. Folge 9, Nr. 1, pp. Circ. No. 1, Rev. annually, 54 pp. mimeo. STiJVE, G., Potentiell und pseudo-Pot. Temp., U. S. WEATHER BUREAU, Instructions for Beitr. z. Phys. d. fr. Atm., Bd. 13, p. 218, airways meteorological service. WB Circ. N., 1927. Aerolog. Div., 4th ed., 1939. SUR, N. K., Latent instability in the atmos- U. S. WEATHER BUREAU, Normal pressure phere and its consequences, Proc. Nat. Inst, change in three hours preceding the observa- 107-116, of Sci. of India, v. 5, no. 1, pp. tion, 4 pp. [maps, for U. S.] 1939. U. S. WEATHER BUREAU, The preparation the prediction air tem- TAKAHASI, K., On of of manuscript maps, W B Circular, 6 pp., perature, Jn. Met. Soc. Ja., v. 17, no. 3, 1939. 1939, p. (9). WILLETT, H. C, Problems in weather map TERASIMA, M., R Uyeda, and Y. Oka, The analysis and forecasting in connection with at height five upper winds in Japan a of transatlantic flying, Jn. Aero. Sci., v. 7, kilometers and attempts to weather fore- 1940, pp. 248-251. casting therefrom, J. Met. Soc. of Japan, v. VERNON, E. M., and E. V. Ashburn, A prac- 13, no. 6, pp. 277-288, 1935 [Abstract in tical method English]. for computing winds aloft from pressure and temperature fields, M. W. R., THOMAS, H., uber funftdgig gegldttete Luft- V. 66, pp. 267-274, 1938. deren vierundzwanzigstiindige druck- und H., Die Begriindung zur Wetter- WAGEMANN, und Differenzenkarten als Hilfsmittel Brauchbarkeit der Guilbertschen Regeln, M. vorhersage, MZ, Bd. 45, pp. 381-385, 1928. Z., Bd. 49, pp. 262-266, 1932. THOMAS, H., Wetterkartenkatalog?, MZ, Bd. WENSTROM, W. H., and W. O. J. Roberts, 50, pp. 229-231, 1933. Regional weather maps, BAMS, v. 18, pp. THORN, W. A., Recent developments in the 41-46, 1937. Meteorological Division, British Columbia ZISTLER, P., Aerologische Aufstiege und BAMS, V. 21, pp. 10-12, 1940. Wetterdiagnose, Deutsch. Flugwetterdienst, TROEGER, H., Eine Wetterkarte mit Aequiva- Erfahrungsberichte, Sonderband 2, pp. 119- lenttemperatur Lindenberg, Mitt. Aaron. 126, 1930. Kinematic Methods

ANGERVO, J., Beispiele zur numerischen DuBfJCK, A. F., ijber Methoden zur Vorav^- Voransberechnung retrograde Tiefdruckbah- berechnung von Wetterkarten, Moscow, Met. nen, Gerl. Beitr. Geophys., Bd. 37, pp. 1-7, Hydrol., 1937, no. 3, pp. 32-38. 1932. GIAO, A., La mecanique differentielle des ANGERVO, J. M., Einige aus der Luftdruck- fronts et du champ isallobarique, France, verteilung herleitbare Gesdtzmdssigkeiten bei Office Nat. Met., Memorial, no. 20, 127 pp., der Bewegung der Hoch- und Tiefdruckzen- 1929. 354-364, 1930. tren, M. Z., Bd. 47, pp. HARNEY, P. J., Note on H. C. Huang's in- ANGERVO, J. M., Einige Formeln fur die vestigation of frontogenesis in the North numerische Vorausbestimmung der Lage und Pacific, M. W. R., v. 65, Sept. 1937, pp. Tiefe der Hoch und Teifdruckzentren, Met. 335-6. Zeit., Bd. 47, pp. 314-315, 1930. KOBAYASI, T., On the mechanism of cyclones ANGERVO, J. M., Wann Ensteht aus einer and anticyclones, QJRMS, v. 49, no. 207, pp. V-Depression ein selfstdndiges Teilminimum 177-189, 1923. Oder aus einem, Keil hohen Druckes ein Hoch- KOBAYASI, T., iJber die Mechanismen der druckszentrum ? Gerl. Beitr. Geophys., Bd. Zyklonen und Antizyklonen, Report of 35, pp. 265-290, 1932. Aeron. Research Inst., Tokyo Imperial ANGERVO, J. M., Zur Theorie der Zyklonen- Univ., V. 1, no. 7, pp. 189-212, 1924. Antizyklonenbahn. Gerl. Beitr. Geophys. und KOUZNETZOV, E. S., To the question about Bd. 34, pp. 45-59, 1931. mathematical basis for methods of extra- ARAKAWA, H;, On the kinematical analysis polation of barical field, Moscow, Met. Hy- of the field of pressure, Jn. Met. Soc. Jap., drol., V. 1937, no. 9, p. 26. V. 14, no. 3, 1936, p. (11) ; Proc. Phys. LAMATSCH, Bruno, Zur Vorausberechnung Math. Soc. Jap., v. 18, 1936, no. 9. der Bewegung von Hoch- und Tiefdruckzen- BLATON. J., Zur Kinematik nichtstationdrer tren nach der Methode von J. M. Angervo, Luftstromungen, Bulletin of the Geophys. MZ, Bd. 50, pp. 137-140, 1933. Soc, Warsaw, 1938. PETTERSSEN, S., Contribution to the theory DeDeBANT, G., La geometric isobariqu^, Pro- of frontogenesis, Geofys. Publ., v. 11, No. 6, ces-verbaux des Seances de I'Assoc. de Met., 1936. I., Lis- 5th Assemblee Generale, U. G. G. PETTERSSEN, S., Frontogenesis and fronts in bonne, 1935. the Atki.ntic Area, Un. Geod. et Geophys. DINKELACKER, O., Graphische Methode zur Intern. 6ieme Ass. Gen., Edimbourgh, Sent., Bestimmung der Verlagerungsgeschwindig- 1936, Proces verbaux de I'Assoc. de Met., keit, und -richtuna eines Tief- oder Hoch- part 2, Mem. et disc, pp. 83-105. 1933. druckgebiets, MZ, Bd. 50, pp. 166-171, PETTERSSEN, S., Kinematical and dynamical DuBiJCK, A. F., To the question about fronto- properties of the field of pressure with appli- genesis and gradient wind. Met. i Hidrol., cations to forecasting, Geofys. Publ. V. 10, 1938, no. 8, pp. 31-63. No. 2, 1933. 206 AIR MASS ANALYSIS

PETTERSSEN, S., On the distribution of SEN, S. N., Mechanism of cyclones in the Bay horizontal divergence in moving pressure of Bengal, Sci. and Culture (Calcutta), v. 3, systems, QJRMS, v. 66, Supplement, pp. 102- pp. 458-461, 1938. 111, 1940. STEVENS, W. R., Relation of pressure changes PETTERSSEN, S., Practical rules for Prog- to cyclones and fronts. M. W. R., v. 66, nosticating the movement and the develop- March, 1938, pp. 68-70. ment of pressure centers, Proces-Verbaux d. s. de I'Assoc. de Met., Pt. 2, Un. Geod. et STiJVE, G., iJber lineare Deformationsfelder, Geophys. Int., 5th Assemb., 1933, Lisbon. Beitr. z. Phys. d. fr. At., Bd. 19, pp. 250- Paris, 1935, pp. 35-70. 271, 1932.

F. HISTORICAL FORERUNNERS OF FRONTAL ANALYSIS

BIGELOW, F H., Studies on the statistics and K6PPEN, W., Beitrdge zur Kenntnis der Boen kinematics of the atmosphere in the United und Gewittersturme, Ann. d. Hydrog., Bd. States, Pt. 5: Relations between the gen- 7, pp. 324-335, 1879. circulation the cyclones and anti- eral and K6PPEN, W., Der Gewittersturm vom 9 Au- cyclones, M. W. R., V. 30, pp. 250-257, May, gust, 1881. Ann. d. Hydrog., 1882, H. 10, pp. 1902. 595-619, H. 12, pp. 714-737. Synoptical representation BJERKNES, V. F., K6PPEN, W., H. W. Dove und wir, M. Z., Bd. v. 36, no. of atmospheric motions QJRMS, 38, pp. 288-292, 1921. 155, pp. 267-286, 1910. (Note also: Synop- tischeDarstellung atmos. Zustande, Veroft. KoPPEN, W., Vsber Boen, insbesondere die Boe vom 9. September 1913, Ann. d. Hydr., Bd. Geophys. Inst. Univ. Leipzig, Ser. I, 1911- 32, pp. 303-320, 1914. 13.) KoPPEN, W., tJber die mechanischen Ursachen BLASIUS, Wm., Storms, their nature, clas- der Ortsverdnderung atmosphdrischer Wir- sification and laws, Phila., 1875, 342 p. bel, Zeit. d. Oest. Gesell. f. Met., Bd. 15, BRILLOUIN, M., Vents contigus et nuages, (Hann Band), 1880, pp. 41-53. Annales du Bureau Central Meteorologique, LEMPFERT, R. G. K., and R. Corless, Line- 1938, Paris. squalls and associated phenomena, QJRMS, CLAYTON, H. H., Studies of cyclonic and an- V. 36, pp. 135-170, 1910. ticyclonic phenomena with kites. Blue Hill LEY, C, The Eurydice squall, Symons' Mo. .Obsy., Bulletin no. 1, 1899, 15 pp., and Bull. Met. Mag., v. 13, pp. 3-39, 1878. no. 1, 1900, 29 pp. (2 memoirs). LEY, C, On the inclination of the axes of 'CLAYTON, H. H., Weather forecasting, MWR, cyclones, QJRMS, v. 5, pp. 167-177, 1879. V. 48, 1920, pp. 83-84. LOOMIS, E., On the storms which were ex- DIECKMANN, A., Fitz-Roy : Ein Beitrag zur perienced throughout the U. S. in the month Geschichte der Polarfrcmttheorie, Die Natur- of February, 18^2, Trans. Am. Philos. Soc, wissenschaften, no. 36, 1931. n. s., V. 9, 1846. DOVE, H. W., The law of storms, 2nd ed., MEINARDUS, W., iJber die absolute Bewegun- London (trans, from German by R. H. gen der Luft in fortschreitenden Zyklonen, Scott), 1862. M. Z., V. 20, pp. 529-544, 1903. (See also DURAND-GReVILLE, M. E., Les grains et Kiewel, Abhand. Preuss. Met .Inst., v. 4, les orages, France, Bur. Centr. Met., Ann., no. 2, 1911 ; and Exner, Ann. d. Hyd., Nov. tome 1, Part B, pp. 250-272, 1892. 1920.) DURAND-GREVILLE, E., La theorie du grain PEPPLER, A., Die Temperaturverhaeltnisse et de I'orage. Paris, Bull. Soc. Astr. France, der freien Atmosphaere am 5-7. Dez. 1906. 1906, pp. 326-336. Beitr. Phys. fr. Atmos., v. 4, pp. 116-127; DEFANT, A., Ueber die Beziehung des Nie- Zur Kenntnis der Luftstroemungen in gros- derschlags zu den Temperatur-und Luft- sen Hoehen ueber Zyklonen und Antizyklo- druckverhdltnissen der Atmosphdre, Beitr. nen, Beitr. Phys. fr. Atmos., v. 6, pp. 73-99.

129-146 ; Phys. fr. Atmos., v. 4, pp. Die PEPPLER, W., Zur Kenntnis der Tempera- in kalten und warmen Windverhdltnisse tur-Inversion, Arb. d. preuss. Aeronaut. Obs. und weitere Folgerungen iiber Luftsdulen Lindenberg, Bd. 8, pp. 255-262, 1913. das Wesen dieser Gebilde, id. v. 5, pp. 161- R. M. and E. L. Hawke, Cycles 178. (See also Sitz. Wien. Akad. Wiss., 2a, POULTER, in meteorological knowledge, QJRMS, v. 60, V. 119, 1910, p. 739). pp. 341-344, 1934. PESSLER, A., Die Kalteeinbriiche in Mittel- RAETHJEN, P., 50 Jahre Zykonentheorie und Europa im Winter 1908/09, M. Z., Bd. 27, die gegenwartige Entwicklung, M. Z,, v. 54, pp. 1-12, 1910. pp. 393-405, 193". TICKER, H. v.. Das meteorologische System SCHMIDT, W.. Ziir Mechanik der Boen, M. Z., von Wilhelm Blasius, Die Naturwissenschaf- Bd. 28, pp. 355-362, 1911; id., 1912, p. 103; ten, Jg. 16, Heft 33, 1928. disc, by Defant. Beitr. Phys. fr. Atmos., v. FITZROY, H., The weather book, 2nd ed., 9, 1920, pp. 98-113. London, 1863. SHAW, W. N., The meteorological as^pects of Feb. 26, 1903, QJRMS, v. 29, HANN, J., and C. Jelinik, Vsber das Luftdruck- the storm of Maximum vom 23. Jdnner bis 3. Febru/ir pp. 233-258. 1903. 1876 nebst Bemerkungen iiber die Luftdruck- SHAW, W. N., and R. G. K. Lempfert, Life Maxima im allgemeinen, Zeit. d. Oest. Ge- history of surface air currents, London, Met. sell. f. Met., Bd. 11, Nr. 9, pp. 129,135, 1876. Off., no. 174, 1906, 107 pp. HAZEN, H. A., On the retardation of the SIMPSON. G., The development of weather maxima and minima of air pressure at high forecasting. XlXth Cen., London, v. 101, pp. stations, Amer. J. of Ssi., v. 24, pp. 105-113, 557-573. 1927. 1882. VINCENT, J., Sur I'origine et la constitution HUNT, H. A., Essay on southerly bursters, des cyclones, Brussels, Acad. roy. de Bel- Sydney, 1894. gique, 1928, 43 pp. BIBLIOGRAPHY 207

WEICKMANN, L., Die Gewitter vom 11 Udrz WUNDT, W., BaroTn&trische Teildepressionen 1910, Ein Beitrag zum Studien der Boen, tend ihre wellenformige Aufeinanderfolge, Deut. Met. Jahrbuch, Bayern, Bd. 33, 1911, Preuss. Met. Inst., Abhandlungen, Bd. 2, Anhang, pp. J 1-8. no. 5, pp. 1-25, 1904.

G. DETAILED ANALYSIS OF SYNOPTIC SITUATIONS

1. North America

1927 and earlier MEISINGER, C. L., The precipitation of sleet and the ANDRUS, C. G., The application of Bjerknes formation of glaze in the eastern lines to the development of secondary lows, United States, January 20 to 25, 1920, with rem,arks M. W. R., V. 49, pp. 11-12, 1921. on forecasting, M. W. R., v. 48, pp. 73-80, 1920. ANDRUS, C. G., Meteorological aspects of the International Balloon Race of 1920, M. MEISINGER, C. L., The Pressure distribution at various levels W. R., V. 49, pp. 8-10, 1921. during the passage of a cyclone across the plateau region of the BJERKNES, J., and M. A. Giblett, Retro- United States, MWR, v. 50, 1922, pp. 347- grade Depression in the Eastern United 356. States, M. W. R., v. 52, pp. 521-527. 1924. ROSSBY, C.-G., and R. H. Weightman, Appli- BLAIR, R., Free balloon ascensions at W. cation of the polar front theory to a series and Indianapolis Sept.- Oct. 1909, Omaha of American weather maps, M. W. R., v. 54, Bull. Mt. Wea. Obsy., v. 3, 1910, pp. 127- pp. 485-496, 1926. 135 ; Sounding balloon ascensions at Indian- SAMUELS, L. T., Note on deep easterly apolis, Omaha, and Huron, Bull. Mt. Wea. winds over the Middle West on January 2U, Obsy.. V. 4, 1911, pp. 183-304. 25, and 26, 1921, M. W. R., v. 49, pp. 13- BROOKS, Charles F., The Ice storms of New 15, 1921. England, Blue Hill Meteorological Observa- SHIPMAN, T. G., The East wind and its lift- tory, Observations and Investigations, 1914, ing effects at Fort Smith, Arkansas, MWR, 77-84. pp. V. 53, 1925, pp. 536-537. F., sleet and how BROOKS, C. The nature of WEIGHTMAN, R. H., Some observations on it is formed, M. E., v. 48. pp. 69-73, W. cyclonic precipitation of Feb. 22-23, 1925, 1920. in central and eastern U. S., MWR, Sept., BROOKS, C. F., Origin of some secondary cy- 1925, pp. 379-384. clones in the Middle Atlantic coast, MWR, 1928 to 1936 V. 49, 1921, pp. 12-13. ANDRUS, C. G., Notes on line squalls, M. W. BROOKS, C. F., Winds and weather of cen- R., V. 57, pp. 94-96, 1929. tral Greenland: Meteorological results of the Swiss Greenland expedition, MWR, v. 51, BAUMANN, G. H., Gronland-Flug von Gro- 1923, pp. 256-260. nau 1931 (Beitrdge zur Meteorologie des Luftweges ilber Gronland, II), Aus dem Ar- Schultz, and Ward, R. DAVIS, W. M., L. G. chiv der deutschen Seewarte, Hamburg, Bd. DeC, An investigation of the sea-breeze. 52, nr. 4, pp. 33-42, 1933. New England Met'l. Soc, Observations, v. BLAKE, D., Mexican West Coast Cyclones, M. 21, Part 1, pp. 214-264, 1888. W. R., V. 63, pp. 344-347, 1935. GREGG, W. R., International aerological soundings at Royal Center, Ind., May, 1926, BLAKE, D., Storm types and resultant precipitation in the area, M. R., v. MWR, V. 55, pp. 293-297, 1927. San Diego W. 61, pp. 223-225, 1933. GROGAN, S. A., Northers on the east coast of BOWIE, E. H., A remarkable occurrence of Mexico, MWR, v. 47, 1919, p. 469-71 ; Heavy cyclones in series, M. W. R., v. 61, pp. 266- rains at Tampico, id., p. 468-9 ; Hot winds at Tampico, id., 1919, p. 234. 267, 1933. HALLENBECK, C, The Topographic thunder- BROOKS, C. F., A period of thunderstorms storms, MWR, V. 50, 1922, pp. 284-287. originating in the upper air, BAMS, v. 17, pp. 315-317, 1936. HAYDEN, Everett, The great storm off the phe- Atlantic Coast of the United States, March BYERS, H. R., Characteristic weather nomena California, Mass. Inst, of Tech. 11-H, 1S8S. Nautical Mon. no. 5, U. S. of Hydrogr. OS., 1888. (See also Upton, Amer. Met. Papers, v. 1, no. 2, 54 pp., 1931. Met. Jn., V. 5, 1888-9, p. 19-37). BYERS, H. R., On the meteorological history the hurricane November, 1935, M. HENRY, A. J., Temperature inversions at the of of W. Mt. Weather Observatory, Bull, of the Mt. R., v. 63, pp. 318-322, 1935. Weather Obsy., v. 1, pp. 143-175, 1908. CAMERON, D. C, Easterly gales in the Co- lumbia River Gorge during the winter of HENRY, A. J., Variations of temperature and — pressure at summit and base stations in the 1930-31 some of their causes and effects, 411-416, 1931. Rocky Mountain region. Bull. Mount M. W. R., V. 59, pp. Weather Obsy., v. 3, pp. 201-225, 1910. CAMERON, D. C, Great dust storm in Wash- ington and Oregon, April 21-21,, 1931, M. W. HENRY, A. J., Daily changes in temperature R., V. 59, pp. 195-197, 1931. up to i.000 meters. Bull. Mt. Wea. Obsy., v. 5, 1912, pp. 1-18. CAMERON, D. C, and A. B., Carpenter, De- tructive easterly gales in the Columbia River JAKL, V. E., An analysis of some free-air Gorge, December, 1935, M. W. R., v. 64, pp. observations in the relation to precipitation, 264-266, 1936. MWR, Aug., 1925, pp. 337-343. CARPENTER, A. B., Behavior of a warm JAKL, V. E., Some observations on tempera- front on the Oregon-Washington Coast, tures at elevations and winds moderate above BAMS, V. 17, pp. 319-320, 1936. the ground, MWR, v. 47, 1919, pp. 367-373. CARPENTER, A. B., Subsidence in maritime MEISINGER, C. L., The Great cyclone of mid- air over the Columbia and Snake River ba- February, 1919, MWR, V. 48, 1920, pp. 582- sins and associated weather, BAMS, Oct., 586. 1935, p. 224 (also MWR, 1936.) 208 AIR MASS ANALYSIS

CHAPEL, L. T., Note on the probable intru- PIERCE, C. H., The cold winter of 1933-3J,, sion of southern hemisphere air to the re- BAMS, v. 15, pp. 61-78, 1934. 243- gion of Panama, M. W. R., v. 61, pp. PIERCE, C. H., The dust storm of November 249, 1933. 12 and IS, 1933, BAMS, v. 15, pp. 31-35,. COOK, A. W., Marked summer air-mass dis- 1934. their placements in California and effects REED, T. R., Gap winds of the Strait of 39-45, 1934. an weather, M. W. R., v. 62, pp. Juan de Fuca, M. W. R., v. 59, pp. 373-376, EMMONS, G., Atmospheric structure over the 1931. southern United States, Dec. 30-31, 1927. SAMUELS, L. T., Sounding-balloon observa- Determined with the aid of sounding bal- tions made at Broken Arrow, Oklahoma, loon observations, M. I. T., Met'l. Course, during the International Month, (Summ. December^ Prof. Notes, No. 9, 1935. 58 pp. 1929, M. W. R., V. 59, pp. 297-309, 1931. in BAMS, V. 17, pp. 268-271, 1936.) SAMUELS, L. T., Sounding-balloon observa- FRENCH, G. M., Windstorm in the Los An- tions at Royal Center, Ind., during the In- geles area November 22, 1930, and som,e ternational Mcnith, September, 1930, M. W. re- effects of wind flow in a mountainous R., V. 59, pp. 417-426, 1931. gion, M. W. R., V. 59, pp. 223-225, 1931. SAMUELS, L. T., Sounding-balloon observa- HALLENBECK, C, Squall lines in New Mex- tions made at Groesbeck, Tex., during the ico, M. W. R., V. 58, pp. 402-405, 1930. International Month, October, 1927, M. W. HOLZMAN, B., Synoptic determination and R., V. 57, pp. 231-246, 1929. cold fronts aloft, forecasting significance of SAMUELS, L. T., Sounding-balloon observa- 400-413, 1936 ; Sum- M. W. R., V. 64, pp. tions made at Royal Center, Ind., during the mary in BAMS, v. 18, pp. 1-5, 1937. International Month, February, 1931, M. W. HUMPHREYS, W. J., On the occasions, or R., V. 60, pp. 12-22, 1932. extratropical cyclones, incidental causes, of SAMUELS, L. T., Special series of sounding- M. W. R., V. 61, p. 112, 1933. balloon observations made during the winter JOHNSON, H. N., The dry chinook wind, of 1929-30, M. W. R., V. 62, pp. 121-128, BAMS, V. 17, pp. 23-27, 1936. 1934. KRICK, I. P., Foehn winds of southern Cali- SCHNEIDER, L. R., Greenland West-coast fornia, Gerl. Beitr. Gteophys., v. 39, pp. 399- foehns: A discussion based on the foehns 407, 1933. of January, 1929, M. W. R., v. 58, pp. 135- 138, 1930. KRICK, I., Brooks, C. F., and Willett, Foehn wind cyclogenesis, BAMS, June-July, 1935, SHOWALTER, A. K., Fronts and depressions pp. 162-164. in the Plateau Region of the United States, 206-208, 1932. LOEWE, F., PilotbaUonaufstiege im Umanaqf- BAMS, V. 13, pp. jord (Westgronland) im Sommer 1932, MZ, SMITH, W. L., Weather problems peculiar to Bd. 52, pp. 155-158, 1935. the New-York-Chicago Airway, M. W. R., v. 503-506, 1929. LOPEZ, R., Ciclones tropicales cruzando el 57, pp. altiplano de Mexico, Rev. de Met. y. Aero- TANNEHILL, I. R., Severe cold waves on the

log., V. 1, no. 6, 1930, pp. 114-28 ; MWR, Texas Coast, M. W. R., v. 56, pp. 41-46, 1930, p. 210. 1928. LOPEZ, E., Estudio sobre Nortes, Mem. y TANNEHILL, I. R., Wet and dry northers, Rev. Soc. Cient. "Antonio Alzate", v. 41, M. W. R., V. 57, pp. 136-142, 1929. 1932, p. 91-108. WAIBEL, Leo, Norder und Fohn in der Sierra LINK, O., Die Kdltewellen in Nordamerika Madre de Chiapas, MZ, Bd. 49, pp. 254-258, und ihr Einbruch in das amerikanische Mit- 1932. telmeergebiet. Diss., Wiirzburg, 1934, 146 p. WARD, R. A., Some notes on the squall of LITTLE, D. M., Some effects of California August Sth, 1936, in the Los Angeles area, mountain barriers on upper air winds and BAMS, V. 17, pp. 329-331, 1936. 376- sea-level isobars, M. W. R., v. 59, pp. WEBER, J. H. and Brooks, C. F., The weath- 383, 1931. er-map story of the flooding rainstorm of McATJLIFFE, J. P., Morning showers over New England and adjoining regions. Novem- the Gulf, and afternoon showers in the in- ber 3-lf, 1927, Jn. New Eng. Water Works terior near Corpus Christi, Tex., M. W. R., Assoc, V. 42. no. 1, March, 1928, pp. 91-

V. 61, pp. 229, 1933. 103 ; reprinted, id., v. 44, no. 1, March, 1930, MASON, W. A., The Santa Ana or desert pp. 106-118. storm of Southern California, Proc. U. S. WEXLER, H.. Analysis of a warm-front-tyve Naval Inst., Jan. 1935, pp. 56-66. occlusion, M. W. R., v. 63, pp. 213-221, 1935. MINSER, E. J., Icing of aircraft. Air Com- WILLETT. H. C, Discussion and illustration merce Bull., Dec. 15, 1934, and reprinted in of problems suggested by the analysis of BAMS, V. 16, pp. 129-133, 1935. atmospheric cross-sections, Papers in Phys. Oceanogr. and Met., Mass. Inst. Techn., v. NAMIAS, J., Structure of a wedge of continental polar aid determined from aerological 4, no. 2, 1935, 41 pp. observations. Mass Inst, of Tech., Meteoro- YOUNG, F. D., Desert winds in southern Cali- logical Course, Prof. Notes, No. 6, 39 pp., fornia, M. W. R., v. 59, pp. 380-388, 1931. 1934. 1937 and later ON Synoptic Conditions for tornadoes. BAMS., V. 20. pp. 50-51, 1939 (Excerpt from: U. S. BLAKE, D., Movement and effects of an un- Met. Yearbook, 1936, pp. 29-30, D. C, 1938.) stable tropical air mass aloft over the far PAGLIUCA, S., The Janvary 1931, cold wave west. August 7-13th, 1936, BAMS, v. 18, pp. on Mount Washington, N. H., M. W. R., 360-364, 1937. V. 62, pp. 57-58, 1934. BLAKE, D., Note on the hurricane of Aug. PARKINSON, G. R., Dust storms over the 5 to S. 1936, in Mexican West-Coast waters, Great Plains: their causes and forecasting, M. W. R., V. 65, pp. 59, 1937. BAMS, V. 17, pp. 127-135, 1936. (See also BLAKE. D., On the origin of tropical air near Samuels, J. Aero. Sci., v. 3, no. 1, p. 52, the western American mainlands, BAMS, v. 1935.) 20, pp. 385-389, 1939 )

BIBLIOGRAPHY 209

BLAKE, D., Unusual fluctuations in the dew- NAMIAS, J., Thunderstorm forecasting with point along the southern California coast, the aid of isentropic charts, BAMS, v. 19, M. W. R., V. 67, pp. 39-41, 1939. pp. 1-14, 1938. BROOKS, C. F., The southerly gale of Jan. NAMIAS, J., Two important factors control- 2U-25, 193S, in the N. E. U. S., BAMS, Jan. ling winter-time precipitation in the south- 1938, p. 46-7. eastern United States, Trans., Amer. Geo- phys. Union, 1939, pt. 3, pp. 341-348. BROOKS, C. F., and L I. SCHELL, Certain synoptic antecedents of severe cold waves OSMUN, J. W. W., Flow patterns in selected in southern New England, BAMS, v. 20, synoptic situations. Mass. Inst. Tech., M. pp. 439-444, 1939. A. Thesis, 1937. (also mimeographed by U. S. W. B., 1937, in revised BROOKS, C. F., and A. H. Thiessen, Mete- form). orology of the great floods in eastern U. S., OSMUN, J. W. W., An introductory discus- Geogr. Rev., April, 1937, pp. 269-290. Re- sion of the isentropic chart, Mimeo. U. S. vised, Smithsonian Inst. Ann. Rept. for 1938, Weather Bureau, Wash., Oct., 1937, 18 pp. pp. 325-348. PIERCE, C. H., The meteorological history BYERS, H. R., Meteorological conditioiis dur- of the New England hurricane, M. W. R ing the March 1936 and other great flood v. 67. pp. 237-286, 1939. storms of the Atlantic seaboard, BAMS, v. PIERCE, C. H., Synoptic analysis of the 18, pp. 132-136, 1937. southern California flood of March 2, 1938, M. W. R., V. DORSEY, H. G., Jr., Local forecasting of 66, pp. 135-138, 1938. heavy winter precipitation at Blue Hill, POGADE, G., Zyklolyse und Zyklogenese an BAMS, V. 19, pp. 281-296; 335 338, 1938. nordamerikanischen Kaltfronten, Ann. der. Hydrographie, DORSEY, H. G., Jr., Some local reversals of Jan. 1938, pp. 32-5. pressure gradient at Blue Hill, BAMS, v. REED, T. R., The unusual windstorm of 19, pp. 453-454, 1938. February 9, 1938, at San Francisco, M. W R., V. GEORGE, J. J., and R. D. Elliott, A new 66, pp. 235-237, 1938. temperature chart, BAMS, v. 20, pp. 105- RILEY, J. A., Aircraft icing zones on the 117, 1939. Oakland-Cheyenne airway, M. W. R., v. 65 HARRISON, H. T., Terminal weather on the pp. 104-108, 1937. Chicago-New York Airway, typecript, 20 ROSSBY, C.-G., J. Namias and R. G. Simmers, pp., charts. United Air Lines, 1939. Fluid mechanics applied to the study of at- HEWSON, E. W., The application wet-bulb mospheric circulations. Part I, A study of of flow potential temperature to air mass analysis. patterns with the aid of isentropic I, analysis, M. I. T. and Woods Hole Oceanogr. Part QJRMS, v. 62, pp. 387-420 ; Part II, Inst., Papers in Physical Oceanogr. v. 63, pp. 7-30 ; Part III, v. 63, pp. 323- and Met., V. 7, 1938. 338 ; Part IV, v. 64, pp. 407-422, 1936-1938. HOLZMAN, B., Sources of moisture for pre- SHOWALTER, A. K., Frontal movements contrary ' cipitation in the U. S., U. S. Dept. of Agric. to the indicated gradient flow pro- Techn. Bull. No. 589, Oct. 1937. duced by minor waves, M. W. R., v. 66 pp 165-174, 1938. HOLZMAN, B., Use of aerological soundings in determining sources of moisture for pre- SHOWALTER, A. K., Relationship of low temperatures cipitation. Trans. Amer. Geophys. Un., 1987, aloft to precipitation. Trans. Pt. II, pp. 488-90. Amer. Geophys. Union, 1939, pt. 3, pp. 352- 353. IVES, R. C, Weather phenomena of the Colo- rado Rockies. J. Franklin Inst., v. 226, no. SWENSON, B., The Ohio and Mississippi River 6, pp. 691-755, 1938. floods of January-February, 1937, M. W. R., Suppl. No. 37, pp. 26-37, 1938. LICHTBLAU, S., Upper-air cold fronts in North America, M. W. R., v. 65, pp. 414- WARD, R. de C, Climates of the United States. 425, 1937. Boston, 1925, 518 pp. (descriptive met., bibliog.) and (with C. F. Brooks LICHTBLAU, S., Weather associated with the and A. J. Connor) The Climates of North floods of March 1936, in U. S. Geol. Survey America. Band 2, Part J of the Koppen-Geiger Water-Supply Paper No. 800, pp. 12-31, 1937. "Handbuch der Klimatologie", Berlin, 1936- 38. (Valuable description, statistics and MANLEY, G., Meteorological Observations of bibliogr. the British East Greenland Expedition, 1935- WAIBEL L., Zum Naturgeschichte 6, at Kanderdlugssuak, QJRMS, v. 64, der 1938, Norther, Geograph. p. 253-76. Zeit., 1938. MINSER, E. J., Studies of synoptic free-air WEIGHTMAN, R. H., Progress in applying new synoptic aids to conditions for icing of aircraft, BAMS, v. day-to-day forecasting, 19, pp. 111-122, 1938. BAMS, V. 20, pp. 169-177, 1939. MINSER, E. J., and G. Hathaway, Synoptic WENSTROM. W. H., Papagayo of March 7, analysis of some excessive rainfalls in the 1939, BAMS. V. 20, pp. 119-121, 1939. Mississippi Basin due to squeezing of trop- WEXLER, R., The filling of the New England ical air between anticyclones, BAMS, v. 19, hurricane of September, 1938, BAMS v. 20, pp. 34-42, 1938. pp. 277-281, 1939.

2. North Atlantic and Caribbean

1927 and earlier FASSIG, O. L., Pilot-balloon observations at San Juan, Porto Rico, MWR, v. 52, 1924, DANISCHEN Meteorologischen Institut and pp. 22-26. Deutsche Seewarte, Tagliche synoptische GEORGII. W.. und H. Seilkoff, Wetterkarten Ergebnisse fur den nordatlantischen Ozean einer flugwissenschaftlichen Forschungsreise und die anliegenden Teile der Kontinente, nach Columbia (S. A.). Aus dem Archiv der 30 vols., 1880-1911, in quarterly parts, Cop- deutschen Seewarte, Hamburg, Bd. 43, nr. penhagen and Hamburg. 3, 56 pp., 1926. 210 AIR MASS ANALYSIS

HURD, W. E., Northers of Mexican and Cen- PORTIG, W., Die Entstehung einer Golfstrom- tral Ainerican waters, U. S. Hydrog. Off., zyklone, Ann. d. Hydr., 1931, H. 4, pp. 197- Pilot Charts of Central American Waters, 199. of various issues, 1927. published on backs PUMMERER. Paul M. und Steiner, R. O., KNOCH, K., iiber die unperiodischen Schwan- Hohenwindmessungen und andere Beobach- kungen der Temperatur im, atlantischen Stil- tungen auf einer flugwissenschaftlichen lengiirtel, Preuss. Met. Inst., Bericht iiber Forschungsreise nach Rio de Janeiro und die Tatigkeit, 1926, pp. 69-84. dem La Plata, Aus d. Arch. d. Deutsch. Seewarte, Bd. 49, Nr. 4, 92 pp., 1930. einer Fahrt MEY, A., Pilotballonaufstiege auf RODEWALD, M., Der Bermuda-Orkan vom 2G bis Dezember 1922, nach Mexiko September April 1933, Der Seewart, Hamburg, 1934, Aus d. Arch. d. Deutsch. Seewarte, Jahr- pp. 119-124. gang 41, Nr. 4, 33 pp., 1923. RODEWALD, M., Meteorologische beobachtun- SEILKOPF H. und Stiive, G., Ergebnisse von gen auf einer Studienfahrt nach Island—mit Hohenwindmessungen auf deni Nordatlantis- bes. Berucksichtigung der Flugmeteorologie, chen Ozean und im, Golf von Mexico, Febru- Ann. d. Hyd., v. 57, no. 11, 1929, pp. 41-53. ary bis Mai 1923, Aus. d. Arch. d. Deutsch. SEMMELHACK, W., Die Staubfdlle im nord- Seewarte, Jahrgang 42, Nr. 2, 38 pp., 1928. west-afrikanischen Gebiet des Atlantischen WAGEMANN, M., ijber die Erwdrmung kalter Ozeans, Ann. d. Hydr., 1934, H. 7, pp. 273- Luft zwischen dem amerikanischen Festlande 276. und den Berm.udas-Inseln, Preuss. Met. Inst., SOLTAU, K. H., Hohenwindmessungen und Bericht iiber die Tatigkeit, 1926, pp. 134- sonstige meteorologische Beobachtungen zwis- 142. chen Hamburg und dem La Plata auf der Einweisungsfahrt von April bis Juni 192S, A. und Kuhlbrodt, E., Pilotbal- WEGENER, Aus d. Arch. d. Deutsch. Seewarte, Bd. 49, lonaufstiege auf einer Fahrt nach Mexiko Nr. 1, 37 pp., 1930. Marz bis Juni 1922, Aus d. Arch. d. Deuts- G., chen Seewarte, Jahrgang 40, Nr. 4, 46 pp., TINGLEY, F. The genesis of a tropical 1922. cyclone, M. W. R., v. 59, pp. 340-347, 1931. WAGNER, F., Die meteorologischen Beobach- 1928 to 1934 tungen wdhrend der Einweisungsfahrt fiir die Hohenwindmessstelle F nach dem La G. H., Gronaufliige 1930/31 auf BAUMANN, Plata im Friihjahr 1931, Aus d. Arch. d. der Nordroute, Deutsch. Flugwetterdienst, Deutsch. Seewarte, Bd. 52, Nr. 3, 52 pp., 99- Erfahrungsberichte, Sonderband 2, pp. 1933. 109, 1930. WHERLE, Ph. et A. Viaut, Les traversees et ECKARDT, B. und Luhe, P., Ergebnisse von tentatives de traversees aeriennes de I'At- Hohenwindmessungen auf dem Ostatlantis- lantique Nord en 1927 au point de vue Me- chen Ozean Idngs der westafrikanischen teorologique, France, Office Nat. Met., Mem- Kiiste im Januar und February 1929: Aus orial No. 19, 235 pp., 1928. d. Arch. d. deutsch. Seewarte, Bd. 51, Nr. 1, 39 pp., 1932. 1935 and later ERICKSON, B. E., Climatology and Meteor- BRANDTNER, G., Seeverkehrsweg : Nord- ology, Pt. VI, Sci. Results of the Swedish- westafrikanische Region des Atlantischen in 1931, Norwegian Arctic Exped. Geogr. Ozeans, Ann. d. Hydr., 1936, H. 11, p. 493. Ann., 1933, pp. 113-145. (Spitzbergen) CRICHTON, J., Iberian peninsula swept by ERNST, W. und Seilkopf, H., Meteorologische severe gales. Met. Mag., vol. 72, 1937, p. Beobachtungen auf dem Las Palm,af-Flug 62-4. der Deutschen Luft Hansa Juni und Juli A. und Helland-Hansen, Bj., Be- 1928, Aus d. Arch. d. Deutsch. Seewarte, DEFANT, richt iiber die ozeanographischen Unter- Bd. 48, Nr. 4, 24 pp., 1930. suchungen im zentralen und ostlichen Teil FASSIG, O. L., The Trade-winds of the east- des Nordatlantischen Ozeans im, Friihsom,- ern Caribbean, Am. Geophys. Un., Trans., mer 193S (Internationale Golfstrom-Expedi- Fourteenth Ann. Meeting, pp. 69-78, 1933. tion), Akademie der Wissenschaften, Ab- GEIGER, R. und Wasner, F., Hohenwinde vor handlungen, Jahrgang 1939, Phys.-math. der westafrikanischen Kiiste im Herbst, Aus Klasse. Nr. 5, 64 pp. [Radiosonde observa- d. Arch. d. deutsch. Seewarte, Bd. 51, Nr. 2, tions] 63 pp., 1932. DUNN, G. E., Cyclogenesis in the tropical GEORGI, J., Meteorologische Beobachtungen Atlantic, BAMS, v. 21, pp. 216-229, 1940. einer Forschungsreise mit "Meteor" auf DURANDIN, P., V. Mironovitch, et A. Viaut, nach Island und Gronland im Sommer 192S, Structure verticale de I'atmosphere en au- der Seewarte, Aus dem Archiv deutschen tomne entre les Azores et les Bermudes. Hamburg, Bd. 49, nr. 3, 74 pp., 1930. France, Office Nat. Met., Memorial, no. 29, KAYE, W. C, and C S. Durst, Some exam- 81 pp., 1938. (Rev. in BAMS, v. 20, pp. ples of development of depressions which 315-18, 1939.) Also art. by Mironovitch and affect the Atlantic, QJRMS, v. 58, pp. 151- Viaut in La Met., March-April 1939, p. 99- 164, 1932. 112. KNOCH, K., und A. Lohr, Ergebnisse von DURST. C. S., The revolving storm of trop- Hohenwindmessungen auf dem Nordatlan- ical origin which travelled across the Atlan- tischen Ozean und dem Karibischen Meer tic in Sept., 1936, QJRMS, v. 63, pp. 355- im April und Mai, 1927, Aus dem Archiv 364, 1937. der Deutschen Seewarte, Hamburg, Bd. 46, ENTWISTLE. F., Atlantic flight and its bear- nr. 2, 44 pp., 1928. ings on meteorology, QJRMS, v. 64, pp. 355- PERLEWITZ. P., Hohenwindmessungen und 391, 1938. andere Beobachtungen zwischen dem Kanal ENTWISTLE, F., The meteorological problem und dem. La Plata Mnrz bis Juni 192k, Aus of the North Atlantic, J. Roy. Aero. See., v. d. Arch. d. Deutsch. Seewarte, Bd. 45, h. 3, 43, no. 338, pp. 69-104, 1939. [valuable pa- 54 pp., 1928. per.] .

BIBLIOGRAPHY 211

EXTERNBRINK, H., Ein Beitrag zum Wet- PORTIG, W., Die Entstehung einer Golfstrom- tergeschehen im Golf von Mexiko, im Kari- zyklone, Ann. der Hydr., Apr. 1939, pp. bischen Meer und auf den Westindischen 197-200. Inseln, M. Z., v. 413-417. 54, pp. 354-359, PORTIG, W., Die Mdchtigkeit der Kdltewellen EXTERNBRINK, H., Kaltlufteinbriiche in die auf dem Atlantischen Ozean, Ann. der Hy- Tropen, Aus dem Archiv der Deutschen See- drogr., Jun. 1938, pp. 314-316. warte, Bd., nr. 57, 7, Hamburg, 28 pp., RODEWALD, M., Die Bedeutung des Drei- 1937. massenecks fur die subtropischen Sturmtief- EROLOV, S., Les cyclones des Antilles en bildungen, Ann. der Hydrogr., Zweites Kop- 1935, Annal. de Phys. du Globe, no. 18, pp. pen-Heft, Sept. 1936, pp. 41-54. 163-168, 1936. RODEWALD, M., Die Bildungsweise einer EROLOV, S., La frontologie aux Antilles, nordatlantischen September^turmzyklone, Ann. de Phys. du Globe de la France d'outre- Ann. d. Hydr., 1936, H. 9, pp. 411-414. mer. An. 5, no. 28, pp. 114-124, 1938. RODEWAL":) M., Die nordatlantsche Lufttein- EROLOV, S., Observations Tneteorologigue en peraturverteilung vor Entstehung einer lan- avion a Martinique, Ann. de Phys. du Globe, glebigen Oktober-Sturmzyklone auf dem 50. no. 20, April, 1937, pp. 41-53. Breitenkreis, Ann. d. Hydr., 1936, h. 6, pp. EROLOV, S., [on weather analyses in the 264-266. Caribbean], Annal. de Phys. du Globe, no. RODEWALD, M., Der "Deutschland"-Orkam 15, pp. 68-69, 77-80, 1935. vom 13 Januar 1938, Ann. der Hydrogr.,

1,AMB, H. H., A visit to Iceland, QJRMS, v. 1938, pp. 243 ff. ; Der Orkan sudlich Neus- 65, no. 280, pp. 244-48, 1939. chottland vom 13-H Jan. 1938, Der Seewart, LOHR, A., Orkanartiger Sturm auf den Azo- Jahrg. 7, 1938, hf. 8, pp. 221-7. ren am 9. Februar 1936, Ann. d. Hydr., RODEWALD, M., Wetterskizzen. Nr. 8: Die 1937, H. 9, pp. 401-406. Entstehungsbedingungen einer Labrador- LOHR, A., Beitrdge zur Flugmeteorologie der strom-Sturmzyklone, Ann. der Hydrog., Bd. h. 371-373, 1936. (C/., Scherhag, Azoren, Aus d. Arch. d. Deuts^h. Seewarte, 44, 8, pp. id., 1937, p. 90.) Bd. 58, Nr. 5, 1938, 45 p., plates. Golfstromzyklonen. syn- LI, S., Untersuchungen iiber Taifune RUDLOFF, W., Eine optisch-dynamische Untersuchung iiber die Veroff. Met. Inst. Univ. Berlin, Bd. 1, h. 5, zyklonen, pp. 34, 1936. Entstehung nordatlantischer Sturm in ausgewdhlten Beispielen., Ann. der Hy- LOCKHART, W. M., Some upper-air observa- drogr., May, 1936, pp. 185-198. (Comments tions made in the Pacific. Trans. Amer. by Scherhag, id., 1936, p. 256.) Geophys. Union, 1939, pt. 3, pp. 348-352. SCHERHAG, R., Die Mdchtigkeit der Kalte- MILDNER P. und Markgraf. H., Meteorologis- wellen auf dem Atlantischen Ozean, Ann. cher Reisebericht u. Hohenwindmessungen der Hydrogr., Jan. 1938, pp. 49-50. auf der Fahrt nach Kamerun Mai bis Juni SCHERHAG, R., Synoptische Untersuchun- 1933, Aus d. Arch. d. Deutseh. Seewarte, Bd. gen iiber die Entstehung der atlantischen 54, Nr. 3, 49 pp., 1935. Sturmwirbel, M. Z., v. 54, pp. 466-469, 1937. MOORHEAD, H. B. F., Remarks on upper-air SCHNAPAUFF, W., Untersuchungen iiber die results obtained during the approach of a Kalmenzone des Atlantischen Ozeans, Veroff. hurricane to Bermudn. August 20-23, 1935, Met. Inst., Univ. Berlin, Bd. 2, h. 4, pp. QJRMS, V. 62, pp. 123-124, 1936. 34, 1937. PIERSIG, Walter, Die Gewitterhdufigkeit im SCOFIELD, E., On the origin of tropical cy- Meeresgebiet vor der nordwestafrikanishchen clones. BAMS, V. 19, pp. 225 ff., 1938. Kilste: ihr jahreszeitlicher Gang und ihre U. S. NAVY, Hydrographic Off., Naval air Verteilung zur Lage der Tropikfront, Ann. pilot. Central America, Washington, 1937, der Hydrog., 1935, pp. 461-466. 282 pp. PIERSIG, W., Schwankungen von Luftdruck ZISTLER, P. und F. M6LLER, Meteorologis- und Luftbewegungen sowie ein Beitrag zum cher Reisebericht und Ergebnisseder Hohen- Wettergeschehen im Passatgebiet des ostli- windmessungen von der Fahrt nach Kame- chen Nordatlantischen Ozeans, Aus dem Ar- run Juli-August 1933, Aus d. Arch. d. chiv der deutschen Seewarte, Hamburg, Bd. Deutseh. Seewarte, Bd. 54, Nr. 2, 41 pp.. 54, Nr. 6, 1936, 41 pp. 1935.

3. North Pacific (and Japan)

1927 and earlier Jn. Met. Soc. Japan, v. 1, no. 3, p. 48-9, no. 61-71; (K. Okubo, id., p. 72-76.) ; no. 5, DAINGERFIELD. L. H., Kona storms, M. W. 4, p. 137-44, 1923. R., V. 49, pp. 327-329, 1921. To- DAIHO, T., On the evolution of secondary NAKIZIMA, H., Upper air currents over the general isobaric depressions off the coast of Tosa in winter. korozawa correlated with Met. Soc. Jn. Met. Soc. Japan, v. 2, no. 7, 1924, pp. weather types in the vicinity, Jn. 206-10. Japan, v. 3, no. 8, 1925, p. 226-231, 1925. HAN'I, K., Southerly wind at Nase as an in- TAMAMURA, M., Evolution of traveling cy- dication of coming rain in Japan. Jn. Met. clones in the Far East, Jn. Met. Soc. Jap., Soc. Jap., V. 3, no. 4, p. 96-102, (15), 1925. V. 3, 1925, p. (31), 294-9, no. 11. (note also 195.) HORIGUTI, H., Life history of the typhoon Tokuyama, id, v. 2, no. 6, 1924, p. on the end of March, 1923, Mem. Imp. Ma- Also Tamura, Cold front of Oct. 15-6, 192Jt, 234-7. rine Obs., Kobe, vol. 2, pp. 9-25. id., v. 2, no. 8, 1924, p. T., cyclone which crossed KOBAYASHI, On a 1928 to 1934 the Korean Peninsula and the variations of its polar front. QJRMS, v. 48, July, 1922, BYERS, H. R., The air masses of the North pp. 169-184 (Abstr. in MWR, 1922, p. 356). Pacific. Scripps Inst, of Oceanography Bul- MISAWA, K., On the glaze storm of the letin, Technical Series, Vol. 3, No. 14, pp. 22nd-23rd Jan. 1923, in Nagano Prefecture, 311-354. 212 AIR MASS ANALYSIS

FUJIWHARA, S., Decay of a cyclone by seg- FUJIWHARA, S., On the evolution of the mentation, Geophys. Mag., Tokyo, v. 4, no. 3, Muroto Typhoon, Kobe, Imp. Marine Obsy., pp. 167-169, 1931. Memoirs, v. 7, pp. 141-159, 1939. FUJIWHARA, S., On the behavior of lines FUJIWHARA, S., On the quick development of discontinuity, cyclones and typhoons in of cyclones by amalgamation, Geophys. Mag., the vicinity of Japan, Geophys. Mag., v. 2, Tokyo, v. 11, No. 1, pp. 41-50, 1937. 1929, pp. 120-131, Tokyo. FUTI, H., Relation of the movement of ty- REED, T. R., Weather types of the northeast phoon to the distribution of temperature at Pacific Ocean as related to the weather of the earth's surface, J. Met. Soc. Japan, v. the north Pacific coast, M. W. R., v. 60, pp. 13, pp. 555-564, 1935. 246-252, 1932. HORIGUTI, Y., The passage on land of the SELGA, M., Pilot balloons and southwesterly Muroto Typhoon, Kobe, Imperial Marine winds at Manila, Philippine Weather Bureau, Obsy., V. 7, pp. 159-192, 1939. Meteorological Note No. 27 (pp. 241-244 of KIZIMA, M., and S. Ooma, On the warm Met. Bull., for Nov., 1933). front on 2\-25 Sept., 1935, in Kwanto Dis- trict, Jn. Met. Soc. Jap., v. 14, no. 5, p. 1935 and later (21), 1936. AOKI, S., Two examples of typhoon consisting KOBE, Imperial Marine Obsy., Daily Weather of main and secondary typhoons, Kyoto Imp. charts of the North Pacific : issued in Univ., Met'l. Research Inst., Met'l. Notes, monthly volumes, 1923-. No. 2, Sept., 1936, 5 pp. (Abstract in English). OGASAHARA, Prof., Introduction to Formo- Misc. Inst. and ARAKAWA, H., Heavy rainfall in Central san frontology. Paper Met. Geophys., Imp. Univ., Japan, 1940. Japan June 2S-July 5, 1938, Jn. Met. Soc. Taihoku Jap., V. 17, no. 1, p. (1). OOMA, S. and M. Utugi, On the development ARAKAWA, H., Die Luftmassen in den of cyclones in the neighborhood of Japan, the relation between the japanischen Gebieten, MZ, Bd. 54, pp. 169- 2nd paper: On 174, 1937. direction of a line of diccontinuity and the development of cyclones, J. Met. Soc. Japan, ARAKAWA, H., The vertical structure of ty- V. 18, pp. 243-256, 1940. phoons, J. Met. Soc. Japan, v. 14, no. 8, 1936, pp. 405-413, 1936. (Abstract in En- OOTANI, T. and S. Yamada, On the depression of China Eastern Sea, Jn. Met. Soc. glish on p. 36 ; repr. in BAMS, v. 17, 1936, 1938. pp. 313-314). In fuU, Beitr. Phys. fr. Atmos., Jap., V. 16, no. 7, p. (23), v. 24, p. 156-61. OOTANI, T., and K. Sone, Heavy rainfall in Jn. Met. ARAKAWA, H., The effect of topography on the Kwanto district in Sept. 1935, no. 1936. the winds and cyclone paths, J. Met. Soc, Soc. Jap., V. 14, 5, p. (19) -(20), Japan, v. 18, pp. 67-68 [summary in Eng. OTUBO, K., Thunderstorm activity and ty- p. (5)], 1940. phoon in western Japan, Jn. Met. Soc. Jap., DEPPERMANN, C. E., Are thunderstorms V. 17, no. 5, 1939, p. (18).

around isolated island stations in the Phi- RODEWALD, M . Das fernostliche Dreimasse- lippines frontal?, Philippine Weather Bu- neck, Ann. d. Hydrog., 1938, pp. 516-519. reau. Meteorological Note No. 9, (pp. 13-18 TAKAHASI, K., Distribution of pressure and of Met. Bull, for Jan. 1936). wind in a typhoon, Jn. Met. Soc. Jap., v. DEPPERMANN. C. E., Are there warm sec- 17, 1939, pp. 422-33, (42). tors in Philippine Typhoons? .Wea. Bur. TAKAHASI, K., On the local rain in Kwanto Manila, 1937, 19 pp. district due to northeasterly wind, Jn. Met. also v. DEPPERMANN, C. E., The Weather and Soc. Jap., V. 18, 1940, p. 175 ; see clouds of Manila, Manila Central Observa- 17, no. 7, p. 261 (27), 1939. tory, Philippines Weather Bureau, 37 pp., TAKAHASI, T., Sudden rise of air-tempera- many plates of clouds, 1937. [Important ture near ground during the night at the contrib. to trop. met.] basin of Kyoto, Kyoto Imp. Univ., Met'l. Research Inst., Met'l. Notes. No. 1, July, DEPPERMANN, C. E, Typhoons and depres- 1936, 4 pp. (Abstract in English). sions originating to the Near East of the Philippines, Philippine Wea. Bur., Manila, TERADA, K., The thunderstorm as a forerun- 21 pp., maps, 1940. ner of the typhoon, BAMS, v. 17, p. 44, DEPPERMANN. C. E., Typhoons Originating circulation the atmos- in the China Sea, Phil. Wea. Bur., 1938. TODYO, S., General of phere and two types of mechanism of falling DEPPERMANN, C. E., Typhoons oriainating rain, Jn. Met. Soc. Jap., v. 18, no. 4, 1940, in the China Sea (Abstract), BAMS, v. 19, p. (14). pp. 375-377, 1938. VISSER, S. W., The Snellius Expedition in DEPPERMANN, C. E., Wind and rainfall the eastern part of the Neth. East Indies, distribution in selected Philippine typhoons, V. 3, Met. Observations, Leyden, 1936, Phil. Wea. Bur., Manila, 1937. 113 pp.

4. Southern Hemisphere

BARNETT, M. A., The cyclonic storms in deutschen Seewarte, 1922, no. 4, 1923, no. 4, northern New Zealand on Feb. 2 and 26 1924, no. 2, 1925, no. 3). of March 1936, New Zealand, Met. Off. Note, no. 22, 34 pp., 1938. BUREAU, R., et al, Radiosondages dans les mer australes, C. R. Acad. Sci. Paris, v. BERICHT Uber den deutschen Atlantischen 208, 1939, pp. 1419-1420. Expedition auf dem Vermessungs und For- schunsschiff "Meteor", Zeit. d. Gesell. f. Erd- COMMISSION REGIONALE No. Ill, (Ameri- la premiere kunde zu Berlin, 1926, No. 1, 5-6 ; 1927, no. que du Sud), Proces verbaux de 5-6. (upper winds and kite ascents in south session, Lima. 1937, Publ. no. 41 Secret, de 1939, pp. Atlantic, cross-sections) : (see also Ann. d. L'Organ. Met. Intern., Leyden,

Hyd., V. 54, 1926, pp. 57-64 ; and Archiv d. 160. :

BIBLIOGRAPHY 213

ESCOBAR, J. S., Notes on the meteorology of MaDE, a., Der Passat im Rossbyschen Dia- Patagonia and Tierra del Fuego, BAMS, v. gramm, Beitr. Phys. fr. At., Bd. 20, H. 1, 21, No. 2, pp. 71-75, 1940. pp. 51-55, 1932. (S. E. trades) GEORGI, J., Pampero secco vom 17 Juli 1935, METEOROLOGICAL CONFERENCE FOR Der Seewart, Hamburg, v. 5, pp. 199-205, THE SOUTHWEST PACIFIC, Minutes of y-Ed, Pampero sudostlich meetings at Wellington, Publ. no. 1936 ; (see also E 1937, 42, vom Rio Grande do Sul, 1927, Ann. d. Hyd., Secret. Organ. Met. Intern., Leyden, 1939, V. 56, p. 3-5.) 92 pp. HEPWORTH, M. W. €., The Relation between MONTS, De, Le front polaire dans I'Ocean pressure, temperature, and air circulation Indien, Annal. de Phys. du Globe, no. 9, over the South Atlantic Ocean, London, pp. 93-5. 1917, 14 Met'l. Comm., M. O. No. 177, p. MONTS, De, La Meteorolopie des Mascarei- (2nd ed.) gnes. Ann. de Phvs. du Globe, no. 14, pp. HESSLING, N. A. Ciclones y Anticiclones eyi 51-52 and 58-62, 1936. Oficina Met. Nac. la Rc-uhlica Argentina, MONTS, De, Role catalyseur de I'air polaire Bol. Men., 1926. dans la genese d'un cyclone tropical, Ann. HOWARD, A. C., South African Meteorology de Phys. du Globe, no. 12, pp. 178-181, 183- Types of atmospheric pressure, their dura- 7, 1935. tion and movements. So. African Jn. Sci., NAVARETTE, J. Bustos, A meteorological V. 16. pp. 273-284, 1920. study of the antarctic region and the at- KIDSON, E., The Canterbury "Northwester" mospheric circulation over the extreme New Zealand Meteorological Office Note No. southern Pacific Ocean, MWR, v. 56, pp. 12, pp. 65175, 1932; (from N. Z. Jn. of Sci. 174-176, 1928. and Techn. v. 14, no. 2, pp. 65-75, 1932.) NAVARRETE, J. B., Meteorological conditions KIDSON, E., The Wairarapa Floods of Aug- on the Santiago (Chile)-Buenos Aires (Ar- ust, 1932, New Zealand Meteorological OfHce gentina) Airway, M. W. R., v. 58, pp. 444- Note No. 13, pp. 220-227, 1933. 446, 1930. KIDSON, E., Meteorological conditions during PUMMERER, P., Aerologische Fluazeugaufs- the first flight across the Tasman Sea, tiege an der Mittel- und Siidbrasilianischen QJRMS, V. 55, 1929, pp. 53-4. Kiiste im Januar-Februar 192S, Deutsch. Flugwetterdienst, Erfahrungsberichte. Son- KIDSON. E., The analysis of weather charts, derband 2, pp. 88-97, 1930 : (see also Ann. d. Australian Geographer, v. 1, no. 5, 14 pp., Hyd., June 1929, 186-92). Jan., 1935. pp. ROOY, M. P. van. Influence of berg winds on KIDSON. E., Flood rains of 11th March 192J,, the temperatures along the West Coast in Hawkes' Bay, N. Z.. N. Z. J. Sci. Techn., of South Africa, QJRMS, v. 62, no. 267, pp. V. 12. no. 1, pp. 53-60, 1930. 528-537, Oct., 1936. (with comments by KIDSON, E.. and J. Holmboe, Frontal meth- Durst, following.) ods of weather analysis applied to the Aus- SCHONLAND, B. F. J. and D. Hodges, Di- tralia-New Zealand area. N. Z., Dept. Sci. rection findinci of sources of atmospherics & Ind. Res., Met'l. Branch, 1935, Pt. I, and South African meteorology, QJRMS, v. Disc. 20 pp., Pt. II. Weather Charts. 66, 1940, p. 23-46. KINZL, H. and G. Wagner, Pilotmifsteigen in SERRA, A. B., Trovoadas locais no Rio de den peruanischen Anden, Gerl. Beitr. (jleoph., Janeiro, Brazil, Divisao de Meteorologia, V. 54, 1938, pp. 29-55. Boletim Mensal, Sept. 1934. LA.MMERT, I.. Frontologische Untersuchun- SPENCER, H. A., Subtropical Meteorology in aen in Australien. Beitr. z. Phys, d. Atm., the Transvaal, Discovery, vol. 7, pp. 100- Bd. 19. pp. 203-219, 1932. 104, 1926. LEIGHLY. J. Marquesan meteorology, Univ. SUCKSDORFF, G., Die Ergebnisse der Unter- Calif. Pub. in Geogr., v. 6, no. 4, pp. 147-72, suchungen an tropischen Gewittern und eini- 1933. gen anderen tropischen Wettererscheinungen. Gerl. Beitr. Geophvs.. v. 55, H. 1, 1939, pp. LOCKYER. Wm. J. S., Southern Hemisphere 138-185. (Africa and Atlantic). Surface-Air CircvJation Solar Physics Com- mittee, London, 1910, 109 p. WADSWORTH, J.. Speed of depressions near the Falkland Islands, Met. Mag., v. 61, p. LOEWE, F., The cold spell of mid-m.arch in 195.1926. Victoria, QJRMS, v. 65, 1939, p. 61-4. WEBSTER, H. C. et al. Thunderstorms in the LOEWE. F., Pressure waves in Adelie Land, Tasman Sea and Coral Sea. March 1934, QJRMS, v. 61, no. 262, pp. 441-444, 1935. Met. Mag., v. 71, 1936, pp. 59-62.

5. E urope 1927 and earlier BJERKNES, J., Practical examples of polar BILHAM, E .G., Pressure type in relation to front analysis over the British Isles in 1915- fog frequency at Scilly during the summer 1926, Geophys. Mem., No. 50. Met. Off., Lon- months. Met. Off. London, Prof. Notes no. don. (Out of print.) Prelim, abstr.. Met. 37, 1924, 5 pp. Mag., March, 1926, pp. 32-33. BILHAM, E. G., Structure of the atraosphere BJERKNES, J., The structure of fronts. Met. over Benson on 3rd March 1920. Met. Off. Mag., V. 61, Mar., 1926, pp. 32-33. Lond., Prof. Notes, no. 21, 1921, 9 pp. BERGERON, T., and G. Swoboda, Wellen und BJERKNES, J., and H. Solberg, Meteoro- Wirbel an einer quasistationdren Grenz- logical conditions for the formation of rain, fldche aber Europa. Veroff. Geophys. Inst, Geofys. Publ., Vol. 2, No. 3, 60 pp., 1921. der Univ. Leipzig, Rd. 3, Hf. 2, Leipzig, In french, Mem. off. Fr. Nat. Met., No. 6, 1924, out of print. Rev'd. in M. W. R., v. 1923) 54, pp. 458-459, 1926. BJERKNES, J., Diagnostic and prognostic BJERKNES, v.. The structure of the atmos- application of mountain observations, Ge- phere when rain is falling, QJRMS, v. 46, ofys. Pub., V. 3, no. 6, pp. 3-35, 1924. pp. 119-140, 1920. 214 AIR MASS ANALYSIS

CALWAGEN, E. G., Zur Diagnose und prog- 1928 to 1934 nose lolcaler Sommerschauer : Aerologische ABSALOM, H. W. L., Storm of Nov. 11-12,. Fhigzeugaufstiege in Ostnorwegen, Geofys. 1929, Met. Mag., Dec. 1929, p. 249-252. Pub., V. 3, no. 10, pp. 3-124, 1926. [ANON], Structure of depressions. Met. Mag.,. CAVE, C. J. P., Winter thunderstorms in the March, 1929, p. 34-37. British Isles, QJRMS, v. 49, 1923, p. 43-53. [ANON], Great snowstorm of Feb. 1933, Met^ DIESING, K., Der Warmeeinbruch (Warm- Mag., March 1933, p. 29-34. front) vom 12. bis IS. Januar 1920 in Mit- BARTNICKI, L., and St. Kolodziejczyk, Con- teleuropa. Veroff. Geophys. Inst. Univ. Leip- ditions synoptique de la formation des zig, Bd. 3, pp. 1-62, 1924. chasse neige en Pologne, Mem. de I'lnst. DINES, L. H. G., Remarkably low base of the Nat. Met. de Pologne, No. 6, 1931. stratosphere during passage a depression. of BERG, H., Aerologische Diagnose einer Auf~ Met. Mag., April, 1926. 68-70. p. gleitfldche, deutsch. Flugwetterdienstes, Er- DOUGLAS, C. K. M., On some summer de- fahrungsberichte, Folge 9, Nr. 4, pp. 25-30, pressions. Met. Mag., 1926, Aug., p. 152-6. Juli 1934. DURWARD, J., A discontinuity of the chan- BERG, H., Anomale Niederschlag in Siid- nel, on March 2U, 1926, QJRMS, v. 52, 1926, deutschland und ihre Bedingungen, Gerl. p. 198-9. Beitr. Geophys., v. 37, pp. 148-166, 1931 FICKER, H. von, Die Ausbreitung kalter Luft BERG. H., Beitrag zur Struktur eines Warm- in RussJnnd and Nordasien, Sitzber. K. K. htfteinbruekes, Gerl. Beitr. Geophys., Bd. Akad. Wiss. Wien, Math.-Nat. Kl., Abt. 2a, 30. pp. 1-39, 1931. V. 119, 1910, pp. 1769-1837. BERG, H., Der Zustand der freien Atmosphiire FICKER, H. von. Das Fortschreiten der am 27. Oktober 1933, Erfahrungsberichte Warmewellen in Russland und Nordasien, des Deutschen Flugwetterdienstes, 8. Folge, Sitz-ber. Wien. Akad. Wiss.. Math.-Naturw. Nr. 14, pp. 121-125, Jan., 1934.

Kl., v. 120, Sec. Ila, June, : 1911, 92 pp. [Cf. BERSON, F. A., Kaltfronten und prdfrontale Henry, Bull. Mt. Wea. Obsy., v. 5, 1912, pp. Vorgdnge ilber Lindenberg in der unteren 1-18, for comp. with U. S. data.] Troposphare, M. Z., Bd. 51, pp. 281-286. FONTSERe, E., Sobre els vents estivals de 1934. conveccio a la casta Catalana, Barcelona, BJERKNES, J., and E. Palmen, Aerologische Inst, de Ciencies, 1918. 63 pp. Analyse einer Zyklone. Beitr. Phys. d. fr. GOLD, E., The travel of depressions. Met. Bd. 21, pp. 53-62, 1933. Mag., April, 53-6. 1926, p. BJERKNES. J., and E. Palmen, Synontische- GOLDIE, A. H. R.. Gustiness of wind in par- o.erologische Untersuchungen eines Kdltein- ticular cases, QJRMS, v. 51, pp. 357-362, briickes. Gerl. Beitr. Geophys. Bd. 32 (Kop- 1925. pen-Band I), pp. 158-172, 1931. INTERNATIONAL commission for the explo- BULL, G. A., Weather conditions over the ration of the upper air. Comptes rendus des central and western Meditterranean during jours internationaux 1923, 192k. (Obtainable the period February 10-li, 1929, London, from Roy. Met. Sc., London). [Elaborate Met. Office, Prof. Notes, no. 60 (v. 4), pp. display of soundings]. 2-8, 1930. KOPP, W. Wie Gestallet sich aus der Friih- CHMIELSKL K., (Etudes sur le temps). Mem. knrte vom 20 Juni 1925 eine Diagnose der de I'Inst. Nat. Met. de Pologne, No. 5, part Wetterlage? Lindenberg Mitt. Aeron. Obs., 1. 1931. pp. 29-35, June 1925 [with cross sections]. CHRISTIANS. H.. Die stratospharische Steue- KUNZ, C, Ueber t^'pische Niederschlagsver- rung in dem kalten February, 1932. Ein tei'ungen in der Schweiz, insbesondere bei Beispiel eines selbststandiaen stratosvhdris- Fohn, Ann. d. Schweiz. Met. Anstalt, An- chen Systems. Synoptis"he Bearbeitungen hang No. 7, 1912, 48 p. Wetterdienststelle, Frankfurt, no. 3, pp. 14-20, 1933. MOESE. O., and G. SCHINZE, Die Schleif- zone vom, 15 und IS Oct., 1926, Das Wetter, CROSSLEY. A. F. and C. W. G. Daking. A Bd. 44, pp. 1-7, 1927. double occhided front at Cardington, QJRMS, 94-96, 1931. MiJGGE. R.. ijber warme Hochdruckgebiete v. 57, no. 238, pp. und ihre Rolle im atmospharischen Wdrme- DIGHT F H.. Conditions in the upper air haushalt. Veroff. GeoDhys. Inst. Univ. Leip- on Oct. 2, 192S, QJRMS, v. 55, 1929, p. zig. Bd. 3. pD. 239-266, 1927. 82-6. NEWNHAM. E. V., The formation of thun- DIGHT. F. H.. Thunderstorm of Nov. 2, 1930;. derstorms over the British Isles in winter. Met. Mag., Dec, 1930, pp. 249-253. Met. Off._ Lond., Prof. Notes, no. 29. 1922, 6 K. M.. The cold spells of Dec.^ pp. (trajectories of air across the Atlantic). DOUGLAS. C 1927, Met. Mag., Jan., 1928, pp. 279-283. READ. R. S.. Cold Fronts Sept. 1, 1925, QJRMS, V. 51, 1925, pp. 416-421. DOUGLAS, C. K. M., The cyclonic devres- sion.-i of November 16 to 23. 1928, QJRMS, READ. R. S., The depression of Feb. 5-7, 1926, V. 56, no. 234, pp. 121-130, 1930. QJRMS, V. 52, 1926, p. 342-4. SCHUBERT. O. von. Bin typisches Beispiel DOUGLAS. C. K. M., The secondary depression fiir den Zusammenhang hoher und niedriger on the niaht of January 28-29, 1927, QJRMS, Luftdruckschwankungen, M. Z., Bd. 44, pp. V. 54, Jan., 1928, pp. 19-26. 310-311, 1927. DURST, C. S., Note on a remarkable temr)era- SPINNANGR. F.. Nedborst oslenfjelds, Natu- ture record at Aberdeen, Met. Mag., Sept. ren, pp. 38-57, 1926. 1928, p. 177-81. SPINNANGR, F., Nedborstudien pa Vestlan- EREDIA, F., Lo Scirocco in Italia, Rome, det. Naturen, pp. 221-238, 1925. Ufficio Presagi, Ann., 5, pp. 155-172, 1932. STiJVE. G., Aerol. Untersuchungen zum Studien- Zwecke d. Wetterdiagnose. Arb. d. Preuss. FALCKENBERG, G., Aerologische Luft- Aeron. Obs. Lindenberg, Bd. 14, pp. 104- reise des Drachevbootes der Rostncket 16, 1922. warte, MZ, Bd. 45, pp. 55-60, 1928. BIBLIOGRAPHY 215

FICKER, H. von, ijber die Entstehung lokaler Beitr. Geophys., Bd. 26, pp. 63-78, 1930. Wdrmegewitter, Sitz. Preuss. Akad. Wiss., (Nachtrag, id., v. 28, p. 235, 1930.) Phys.-Math. Kl., 1931, h. 3, 1932, h. 16, READ, R. S., Warm front fog. Met. Mag., v. 1933, h. 14, 1934, h. 29. 66, 1931, p. 68-9. FONTSERe, E., Die "Ilevants" der katalanis- REIDAT, R., Gewitterbildung durch Kaltluf- chen Kiiste, Beitr. z. Phys. d. £r. Atm., Bd. teinbruch in der Hohe, Beitr. z. Phys. d.. 15, pp. 55-60, 1929. Atm., Bd. 16, pp. 291-297, 1930. GARNETT, H. and Heywood, G. S. P., Notes REINHARDT, H., Aerologie der Warmfront on a cold front on the 23rd of May, 1929, voin 22. Febrvxir 1934. Erfahrungsberichte- QJRMS, v. 56, April, 1930, pp. 186-191. des deutsch. Flugwetterdienstes, 8. Folge, GIBLETT, M. A., Line squalls, J. Roy. Aeron. Nr. 22 bis 26, pp. 183-186, April, 1934. Soc, V. 41, 1927, pp. 509-549 ; abstr. on ROSSBY, C.-G., Studies in the dynamics of backs of some of the Pilot Charts of the the stratosphere, Beitr. z. Phys. d. Atm., Hydrographic Office, U. S. N., since 1929, Bd. 14, pp. 240-265, 1928. Rev., Jan., 1928, and reviewed in Mo. Wea. SCHERHAG, R., Die Entstehung der Ostge- p. 7-11. witter, M. Z., Bd. 48, pp. 245-254, 1931. a cold front. Met. GOLD, E., Diffusion on SCHERHAG, R., Die Bedeutung der Divergenz 37-38 ; comments, pp. 65-66. Mag., 1932, p. fiir die Entstehung der Vb- Depressionen. GOLDBERG, J. und M. Kovacevie, Der Aerologische Analyse der Wetterentwicklung- Schlammregen in Jugoslavien am 3. und U. vom 17 bis 26 Juli 1930. Ann. d. Hydr., Mai 1933 (Ein Beitrag zur Kenntnis des Bd. 62, pp. 397-406, 1934. Mittelmeerzyklonen) . Kro- Scirocco und der SCHREIBER, K., Analyse der Wetterlage vom atische Geog. Zeitschrift, Zagreb, 1934, Nr. 4. bix 8. Januar 1912: Ein Beitrag zur 5. Bjerknes'schen Methode, Aus dem Archiv HARTENSTEIN, G., iJber Vertikalbewegun- der deutschen Seewarte, Hamburg, Bd. 50, gen an der Vorderseite eines Hochdruckge- nr. 4, 58 pp., 1931. Bearbeitungen, Wetter- bietes, Svnoptische SCHR6DER, R., Die Regeneration einer Zyk- no. 1-27, 1934. dienststelie Frankfurt, 6, pp. lone iiber Nord-und Ostsee (Analyse der HERRMANN, M., Scirocco-Einbriiche in Mit- Wetterepoche 29, September bis 3. Oktober teleuropa (Ein Beitrag zur Analyse der 5- 1912). Veroff. Geophys. Inst. Univ. Leip- b-Depressionen vom 25. April und 16, Mai zig. Bd. 4, pp. 49-116. 1929. 1926). Veroff. Geophys. Inst. Univ. Leipzig, SCHWERDTFEGER, W., Temperaturverhdlt- Bd. 4, pp. 181-252, 1929. (Comment by nisse in einem Polarluftaushruch, Erf. Ber. Petitjean, Met., 1931, p. 459-462.) La d. deutschen Flugwetterdienstes III. Sonder- HERSTR6M, E., Zur atmosphdrischen Steuc- band, pp. 35 ff., 1932. Synoptisfhe Bearbeitungen, Wetterdi^ rung, STENZ, E., u6er den grossen Staubfall 26.-30. 1934. enststelle Frankfurt, no. 5, pp. 1-29, April 1928 in Siidostmropa. Gerl. Beitr. HEYWOOD. G. S. P.. Analysis of cold fronts Geophys., Bd. 34, pp. 313-337, 1931. over Leafield, v. 58, no. 244, pp. QJRMS, STiJVE, G.. Die Umgestaltung der stratosphd- 202-206, 1932. rischen Steuerung vom 1.-8. Oktober 1932, MARKGRAF. H., Druckfall im Warmsektor, Synoptische Bearbeitungen Wetterdienststelle, Beitr. z. Phys. d. Atm., Bd. 19, pp. 71-78, Frankfurt, no. 2, pp. 10-12, 1933. 1932. SUTCLIFFE, R. C. Barometer fluctuations at MARSHALL, A. L., The thunderstorms of Malta, Met. Off. Lond., Prof. Notes no. 62, June 1933, QJRMS, v. 59, 1933, p. 416-21. 1931, 10 pp. MOLTCHANOFF, P., Die Methode der Radio- SUTCLIFFE, R. C, The importance of Atlan- sonde und ein Versuch ihrer Anwendung bei tic ship observations for Mediterranean fore- der Erforschung der hoheren Atmosphdren- casting. Met. Mag., Feb., 1930, pp. 18-20. schichten in Polarregionen. Gerl. Beitr. dem THOMAS, H., Das Zusfandekommen eines Geophys., Bd. 34, pp. 36-56, 1931. Druckanstiegs von 35 m.m durch eine.n MuGGE, R.. Die stratasvhdrische Steuerung stratosphdrischen KaWufteinhruch ohne Mit- wdhrend der Knlteperiode im February 1929, wirkung troposphdrischer Vorgdnge, Sitz.- Synoptische Bearbeitungen Wetterdienst- Ber. d. nreuss. Akad. Wi!=s., Berlin, Phys.- stelle, Frankfurt, no. 1, 8 pp., 1932. Math. Kl., 1934. pp. 222-236. NEWNHAM. E. V., Observations of tempera- WALTERS, A., Periodic pressure oscillations ture and humidity in certain occluded cy- at Malta, Met. Mag., Feb. 1933, p. 1-5. clones (rev. of Ciel et Terre, Jaumotte, WEICKMANN, L., und Moltchanoff, Kurzer 1927), Met. Mag., Feb. 1928, pp. 6-8. Bericht iiber die meteorolonisch-aerologi- NOHASCHECK, H.. Der Zustand der freien srhen Beobachtungen auf der Polarfahrt des Atmosphdre bei Nebelfrost-und Glatteiswet- "Graf Zeppelin", M. Z., Bd. 48, pp. 409- terlagen. Aus dem Archiv der deutschen See- 414, 1931. warte, Hamburg, Bd. 50. nr. 3, 19 pp., 1931. ZIERL, Hermann, Die Ausbreitung der Warm- PALMeN, 'E.,Aerologische Unterschungen der luft am 19. November 1930 und ihre Ablo- atmosphdrischen Storungen mit besonderer sung durch eine polare Welle am 23. Novem- BerUcksichtigung der Stratosphdrischen Vor- ber 1930, Deutsches Met. Jrb. f. Bayern, a^.nge. Mitt. d. Inst. d. Univ. Helsingfors, 1930 Anhang H, 7 pp. No. 25, 1933. 1935 and later PALMeN. E., Die Beziehung zwischen troposphdrischen und stratosphdrischen Tempera- R. T., Wave motion in the upper tur und Luftdruckschwankunpen, Beitrage ANDREWS, air. Met. Mag., v. 72, 1937, p. 156-160. z. physik d. fr. Atmosphare, Bd. 17, Hf. 2, pp. 102-116, 1931. BATTY, R, P., Thunderstorms associated with Mag., Nov., 1935, pp. PALMeN. E., Ein Fall der Regeneration einer a warm front. Met. sterbenden Depression, M. Z., Bd. 46, pp. 233-234. 66-69, 1929. BENDER. Kurt, Die Friihjarhsfrdste an der PALMeN. E.. Die vertikale Mdchtigkeit der Unterelbe und ihre Bekdmpfung, Zeit. fiir Kdlteinbriicke Uber mittel Europa, Gerl. angew. Met., Jg. 56, pp. 273-289, 1939. 216 AIR MASS ANALYSIS

BERG, H., Zur Aerologie der Okklusion, GAIGEROV, S. S., Six tornadoes in Central Beitr., z. Phys. d. fr. Atm., Bd. 22, pp. 12- Provinces of European part of USSR and 24, 1935. their synoptical conditions, Moscow, Met. Hydrol., 1939, no. 44-54. BEST, A. C. and L. Dods, Heavy rainfall at 5, pp. Malta, Feb. 19-20, 193S, Met. Mag., v. 73, HARTMANN, W. Kantzenbach, "E. und 1938, p. 150-4. Hansch, F., Zur Aerologie des Kaltluftvors- tosses vom IJ,. bis 16 Oktober deutsch. B6HMS, G., Analyse der Schwergewitter vom 193A, Flugwetterdienstes, Erf ahr ungsber ichte, 9. September 193i in der Schweiz, M. Z., Folge 9, Nr. 15, pp. 81-84, Feb., 1935. Bd. 53, pp. 58-63, 1936. T. W., Gale Oct. 18-20, 1935, Met. BRAZELL, J., The blizzard of Feb. 27-Uarch JONES, of Mag., Nov. 1935, p. 225-8. 1, 1937, Met. Mag., v. 72, 1937, p. 36-38. BULL, G. A., Wave motion in the upper air. KOCH, H.-G., Einfaehanschnitte bei verschiedenen Wetterlagen, Beitr., z., Phys. d. fr. Met. Mag., v. 73, pp. 231-235, 1938. Atm.. Bd. 25, pp. 171-188, 1939. CHEKHOVICH, S. N., Synoptical conditions H., Die Energie des of the snowstorms on the railways of the KOSCHMIEDER, Sturmes Soviet Union during southern cyclonic in- vom 27 Jan. 1932, Fors^hungsarbeiten des staatl. Obs., Danzig, 1935, Heft 5. vasion. Moscow, Met. Hydro!., 1936, no. 9, pp. 10-32. KtJNNER, J., Vertikalschnitte durch Kalt- DAMMANN, W., Ursachen und Verbreitung fronten, M. Z.. v. 56, pp. 249-263, 1939. der Niederschlage vom 4. zuni 5. August KUPFER, E., Frontbildung durch ein "hohes^' 193 Jf im studlichen und siidostlichen Bayem, Steiggebiet, Ann. d. Hydrog., 1938, pp. 251- M. Z., Bd. 52, pp. 140-182. 1935. 254. DEUTSCHE Seewarte, Tagliche Wetterber- KUPFER, Egon, Die Zyklonenfamilie vom 12. icht. Hamburg. [Issued daily, 8 pp., con- bis 20. Mai 1935, MZ, Bd. 52, pp. 313-317, tains fullest tables of daily reports and up- 1935. per air data for Europe and North Atlantic, KURSANOVA-ERVIE, A., Synoptical condi- with maps.] tions of Fohns in Crimea, Moscow, Met. DIGHT, F., The gale of Jan. 12, 1930, Met. Hydro., 1939, no. 9, pp. 34-51 [in Russian].

Mag., Feb. 1930, p. 1-6 ; Gale of Jan. H-15, Le GALL, Les types de temps du sud ouest de 1938, id., V. 73, 1938, p. 4-8. la France, La Meteorologie, v. 10, 1937, pp. DINIES, E., Die Steuerung bei dem winter- 307-408. lichen Wdrmeeinbruch vom 2i. bis 26. De- MACHT, H. G., Skaggerrak-Zyklonen, Veroflf. zember 1929, Ann. d. Hydrog., 1938, pp. Geophys. Inst. Univ. Leipzig, Bd. 9, pp. 86-89. 103-217, 1937. DINKELACKER, O., Beitrage zur Luftmas- MaRZ, Erhard, Das Aprilwetter und seine senanalyse, M. Z., v. 55, pp. 12-18, 1938. Schauerserien, Dissertation, Leipzig Univ., DOUGLAS, C. K. M., Frost and snow in De- 1936, 68 pp. cember and January, Met. Mag., v. 74, no. MIEGHEM, J. van., Analyse aerologiaue du 877, pp. 12-18, 1939. Cyclone du 17-19 decembre 1936 sur I'Europe DOUGLAS, C. K. M., Some notes on the April Occidentale, Belgium, Inst. Roy. Met., Anticyclone, Met. Mag., v. 73, 1938, p. 84-6. Memoires, v. 10, 42 p., 1939. MEIGHEM, J. Van, Analyse aerologique d'un DOUGLAS, C. K. M., Thunderstorms . . . Inst. Roy. [various articles]. Met. Mag., Oct. 1929, p. front froid remarquable. Mem. 1937. Crit. Scher- 213; Aug. 1929, p. 156; Oct. 1932, p. 210; Met. de Belgique, v. 7, by 130-1. April 1933, p. 53-60, 85-6; Sept. 1932, p. hag, Ann. d. Hyd., 1939, pp.

186-190 (with E. L. Hawke) ; v. 73, 1938, MIEGHEM, J. Van, Sur' V Existence de I'air p. 195-202. tropical froid et de I'effet de foehn dans DOUGLAS, C. K. M., The thunderstorms of I'atmosphere libre, Mem. Inst. Royal Met. August, 193S, Met. Mag., v. 73, pp. 195-202, de Belgique, v. 12, 32 pp., 1939. 1938. MIRONOVITCH, V., and A. Viaut, Sur I'air DOUGLAS, C. K. M., A thundery spell in tropical maritime instable. La Met., 1938, July, 1939, and some previous thundery pp. 217-42. periods. Met. Mag., v. 74, pp. 193-199, 1939. MONTANARI, D., Invasione di aria fredda DROZDOV, M. P., Conditions of the summer suW Italia settentrionale nei giorni 24 e 25 transforination on the air masses in the luglio 1939, Rivista di Met. aeronautica, Moscow reqion. Moscow, Met. Hydrol., 1936, anno 3, no. 3, pp. 14-25, 1939. no. 5, pp. 36-40. NEUMANN, E., Die Rolle der Zirkulations- DUHM, Hans, ijber die Niederschlage w'ihrend leistung und der horizontalen Stromungsdi- der Vb-Wetterlacie vom 21-23. Oktober vergenz bei der Westwetterlage vom. 14.-16. 1935, Diss. Fr.-Wilhelms-Univ. Berlin, 1938. Februar 1935, Berlin. Reichsamt fiir Wetter- dienst, Wissensch. Abh., Bd. 4, Nr. 6, pp. EKHART, E., Die grnsse KnJteeinhruch Ende 1-21, 1938. Nov., 1930. Gerl. Beitr. Geophys., Bd. 53, pp. 161-202, 1938. [Very detailed analysis POGOSJAN, K. P., The inversion of the of cold wave crossing the Alps.] subsidence in the conditions of the north- EVJEN, S., ijher die Vertiefung von Zyklo- west of the Soviet Union, Moscow, Met. nen, M. Z., Bd. 53, pp. 165-172, 1936. Hydrol., 1936, no. 10, pp. 41-51. FABRIS, C, Contatti di masse d'aria e preci- RODEWALD, M., Ein hemerkenswerter Fbh- pitazioni svlla regione Veneta, Atti del 13 neinbruch in der freien Atmosphdre, Ann. d. Congr. Geogr. Italiano, 22 pp. Hydr., 1936, h. 6, pp. 267-268.

FIRESAH, A. M., The distribution of wet-bulb RODEWALD, M., Der Hamburger Dauerregen potential temrierature in four selected cy- vom 7. November 1934, Ann. d. Hydr., 1937, clones, QJRMS, V. 65, pp. 397-410, 1939. H. 9, pp. 407-412. FOITZIK, L., Die Untersuchung eines Kalt- RODEWALD, M., Das norddeutsche Hoch- lufteinbruches durch Serien-Aufstiege, M. Z., druck-Gewitter vom 19. August 1932, Ann. Bd. 57, pp. 115-120, 1940. d. Hydr., 1936, H. 4, pp. 143-152. )

BIBLIOGRAPHY 217

SCHKRHAG, R., Die aerologischen Entwick- SCHERHAG, R., Vereisung durch Luftmasse- lungshedingungen zyklonaler Bora, Ann. d. numwandlung, ( Wetterkizzen, Nr. 3S), Ann. Hydr., 1937, H. 6, pp. 286-289. der Hydrogr., May 1938, pp. 257-259. SCHERHAG, R., Die Entstehung der Vb-De- SCHNEIDER, Adelin, Untersuchung der Kdl- pressionen. Ann. der Hydrogr., Zweites tewellen vom 12. bis 20. Mai 1935, Disserta- Koppen-Heft, Sepr. 1936, pp. 66-74. tion, Fr.-Wilhelms-Univ., Berlin, 1936, 31 SCHERHAG, R., Die Entstehung des Kanal- pp. Starmtiefs vom 23. Oktober 1937, Ann. d. SCHR6DER, B., Untersuchungen iiber die Bil- Hydr., 1938, H. 2, pp. 83-85. dung einiger Mittelmeerdepressionen, Verofif. SCHERHAG, R., Die Entstehung des Nordsee- Marineobs. Willemshavn, N. F., Heft 6, 1936, Orkantiefs vom 19. Oktober 1935, Ann. d. 62 pp. Hydr., 1936, h. 4, pp. 153-159. SCHWERDTFEGER, W. und R. Schiitze. SCHERHAG, R., Ein Grenzfall atmospharis- Wetterflug in einem Wdrmegewitter, Zeit. fiir cher Steuerung : Die Bodenisobaren Steuern angw. Met., Jg. 55, pp. 137-142, 1938. ein Hohentief, Ann. d. Hydr., 1937, H. 1, SEIFERT, G., Instabile Schichtungen der pp. 27-37. AtmosphUre und ihre Bedeutung fiir die SCHERHAG, R., Die Kreis- und Schleifensteu- Wetterentwicklung im, Konigsberger Gebiet, rung des europdischen Regengebiets vom 18. Veroff. Geophys. Inst. Univ. Leipzig, Bd. bis 22. Juni 1937 und die Entwicklungsbe- 6, pp. 223-379, 1935. dingungen des dabei entstandenen Nord- SELLENSCHLO, H., Der Nordseeorkan vom seesturms, Ann. d. Hydr., 1937, H. 8, pp. 27. Oktober 1936, Ann. d. Hydr., 1939, H. 388-390. 9, pp. 443-451. SCHERHAG, R., iJber due Niederschlagsbil- STURM, H., Kaltluftzirkulation auf der Riick- dung an Fronten: Der Frontalregen im seite einer Zyklone, Ann. der Hydrogr.,

Warmluftgebiet . vom 3./ 4.. Januar 1932, Aug. 1937, pp. 354-367. Ann. der Hydrog., Bd. h. 30-37, 43, 1, pp. THOMAS, H., Lassen sich die grossen Nieder- 1935. schlag sintensitdten an quasistationd-ren Fron- SCHERHAG, R., Untersuchungen au'sgewdhlter ten im Sommer zahlenmdssig durch ein- europdischer Zyklonen durch Serien-auf- faches Aufgleiten erkldren? M. Z., v. 54, stiege, Ann. der Hydrog., Apr. 1938, pp. pp. 164-169, 1937. 198-201. TORBINA, N. v.. Synoptical conditions of SCHERHAG, R., Die unvermittelte Entwick- thunderstorms on the European territory Hydrol., no. lung der Vb-Depression vom 6./8. Juli 1929 of USSR, Moscow, Met. 1937, im, Gebiet starker Isothermenund Stromungs- 2, pp. 3-25. divergenz, Beitr. z. Phys. d. Atm., Bd. 22, WIESE, W. J., The Novaya Zemlya bora, pp. 76-87, 1935. BAMS, V. 19, no. 9, 1938, p. 410. Asia

1934 and previous Met. Inst., Bericht iiber die Tatigkeit, 1930, pp. 67-81. ASHBEL, D., Das Klima Palaestinas. A : Die Niederschlagsverhaltnisse im sudliche Liba- HAUDE, W., Monsunbeobachtungen am Siidos- non, in Palaestina und in nordlichen Sinai. trande der mongolischen Steppe im Juni und Berlin, 1930, 77 pp. (Bibliog; weather types, Juli 1927, Beitr. z. Phys. d. fr. Atm., Bd. synoptic studies, cold waves into central 17 pp. 22-39, 1931. Africa. LEE, J., A preliminary study on the appli- BANERJI, B. N., Meteorology of the Persian cation of polar front theory to the winter Gulf and Mekran, Calcutta, 1930. cyclones along the lower Yangtse Valley, China, Nat. Res. Inst. Met., Memoir, no. 2, BASU, S. and Desai, B. N., A Discussion on 51 1930. the structure of the inner zone of some In- pp., dian cyclones, Gerl. Beitrage z. Geophysik, LI, Sjan-zsi, Bemerkungen iiber den Einfluss Bd. 42, 1934, pp. 353-364. der Wiiste Taklamakan auf die Witterung in Tjarchlik, MZ, Bd. 51, pp. 296-301, 1934. BASU, S., and S. K. Pramanik, A note on the rapid fluctuation of atmosnheric pressure LOEWE, F., Ergebnisse von Studienfliigen and the atmospheric instability at Peshawar nach und in Persien 1928. Beitr. z. Phys. d. during 1928-1929, India Met. Dept., Sci. fr. Atm., V. 17, pp. 126-175, 1931. Notes, V. 5, no. 53, pp. 69-88, 1931. MAL, S., and B. N. Desai, A study of the CHAD, Shu, Squalls and Gales observed at structure of the Bay storm of November, Tsing Hua Yuan, Peiping for the year 1932, 1926, India Met. Dept., Sci. Notes, v. 4, no. Tsing Hua Univ. Met. Obsy., Quart. Met. H9. pp. 87-100, 1931. Bull., Supplement, 17-28, 1932. (In pp. PETERS, S. P., Note on a cold front at Che- English) foo, N. China, May 15, 1928, QJRMS, v. 55, DEJORGIO, v.. La tempete du 30 Mars, 1929, no. 229, pp. 86-88, 1929. dans le bassin du Tesek et de la Sounja, J. P., observations upper air of Geophys., Moscow, v. 3, no. 3, pp. 326- PETERS, Some of 338, 1933. temperature in Iraq, Lond., Met. Off., Prof. Notes no. 59, 1930, 11 pp. DEJORGIO, v., Le verglas qui a lieu le 13- 15 Dec. 1930 dans la region du chemin de RAMANATHAN, K. R., and H. C. Banerjee, fer a Krasnodar, J. of Geophys., Moscow, A study of two pre-monsoon storms in the V. 3, no. 3, pp. 310-325, 1933. Bay of Bengal and a comparison of their in DESAI, B. and S. Mai, Vertical structure of structure with that of the Bay storms the surface of discontinuity between conti- the winter months, India Met. Dept., Sci. nental and monsoon air masses in the pre- Notes, V. 4, no., 34, pp. 35-47, 1931. monsoon period, Beitr. Ger. Geophys. v. 40, RAMANATHAN, K. R., and K. P. Ramak- pp. 12 ff., 1933. rishnan. The Indian southwest monsoon and HAUDE. W., Die Ausbreitung und Auswirkung the structure of depressions associated with von KalteweUen in den zentralen Wiisten- it, India Met. Dept., Memoirs, v. 26, pt. 2, gebieten Asiens im, Winterhalbjahr, Preioss. pp. 13-36, 1933. 218 AIR MASS ANALYSIS

ROY, S. C, and Mr. A. K. Roy, Structure and HAUDE, W., Neue Forschungen in Mittelasien inovement of cyclones in the Indian seas, und Tibet: Die meteorologische Arbeiten, Beitr. z. Phys. d. fr. Atm., Bd. 16, pp. 224- Pet. Mitteil., v. 81, pp. 288-289, 1935. 234, 1930. HSU, G., The drought and flood of Lhasa, SCHOSTAKOWITSCH, W. B., Die Bedeutung (abstract in English), Met. Mag. (China), des Windes fiir das Klima Ost-Sibiriens, M. V. 13, No. 1, p. 24, Jan., 1937. [monsoon Z., Bd. 44, pp. 101-105, 1927. crossing Tibet] (See also Lu, QJRMS, v. 65, SEN, S. and G. Chatterjee, Himalayan mete- 1939, p. 297). orology. In: H. Ruttledge, Everest, 1933. JAROSLOVTZEV, J. M., Some peculiarities SOHONI, V. v.. Temperature changes in Cal- of synoptical analysis in Middle Asia, Mos- cutta thunderstorms, India Met. Dept. Sci. cow, Met. Hydrol., 1939, No. 6, p. 26. Notes, V. 4, no. 33, 1931. KURGANSKAJA, Y. M., Synoptic conditions SOHONI. V. v.. Weather types associated of snow storms on the railroad of Western with Nor'westers in Bengal, J. and Proc, Siberia. Moscow, Met. Hydrol., 1936, no. 1, Asiatic Society of Bengal, n. s., v. 28, no. pp. 41-50. 1, pp. 349-357, 1932. LI, S. Z., Die Typen ostasiatische Kdltenwel- SUNG, S. W., The extratropical cyclones of len, Gerl. Beitr. Geophys., Bd. 48, pp. 188- eastern China and their characteristics. 192, 1936. (Die Kalteeinbruche in Ostasien, China, Nat. Res. Inst. Met., Memoir, no. 3, Diss. Berlin, Ohlau, 79, pp. 1935). 60 pp., 1931. LU, A., The cold waves of China, China, Nat. SUR, N. K., On the physical characteristics of Res. Inst. Met., Memoir, no. 10, pp. 6-33, fronts during the Indian southwest monsoon, 1937. India Met. Dept., Memoirs, v. 26, pt. 3, pp. LU, A., The spring thunderstorms of the 37-50, 1933. Szechwan Basin, (Abstract in Eng.), Met. VERYARD, R. G., A preliminary study of a Mag. (China), v. 14, no. 5, pp. 219-220, tornado at Peshawar, India Met. Dept., Sci. Dec, 1938. Notes, V. 5, no. 56, pp. 109-116, 1933. LU, A. and Hsu, C. M., The rainfall distribu- "WALKER, G. T. and K. Rav, Rainfall txjpes tion of the summer cyclones of eastern China in India in the cold weather period Dec. 1 (Abstract in English). Met. Mag. (China), to March 15. Mem. India Met. Dept., v. 24, V. 12, no. 8, p. 397, Aug., 1936. no. 11, p. 347-55. 1925. MAL, S , and B. N. Desai. The mechanisî of thundery conditions at Karachi, QJRMS, v. 1935 and later 64. pp. 525-537, 1938. MALIK, S. A., Masking of fronts 'w Cauca- ASHBEL, D., Conditions of winds on the sus, Moscow, Met. Hydrol., 1939, No. 6, p. western s-ûthern and shores of the Sea of 34. Galilee, Met. Mag., v. 71, 1936, p. 153-5. OCKENDEN. C. V.. High altitude vHot bal- ASHBEL, D.. Great floods in Sinai Peninsula. loon ascents at Habbaniya, Iraq, QJRMS, v. Palestine, Syria the and Syrian Desert, and 65, 1939. p. 551-3. the influence of the Red Sea on their forma- S. K., of tion, OJRMS, V. 64, no. 277, pp. 635-639, PRAMANIK, Forecasting nor'westers Oct., 1938. in Bengal. Proc. Nat. Ins^. of Sci. of India, V. 5, no. 1, pp. 93-100, 1939. BLEEKER, W., Meteorologisches zu den 3. hollandischen Karakoram- Exped.. Proc. OOMA. S.. On the development of cyclones in the Kon. Akad. Wet., Am<;terd=im, v. 39, 1936. neighborhood "f Jannn. J. Met. Soo. Japfin. V. 17. np. 356-3G6 in Eng. nos. 6-8, 27 pp. (Rev'd., Met. Mag., v. 72, [Summary pp. 109-112). p. (33)], 1939. P. R., Squalls BRTJZON, E., La peri'^de du crachin sur les KRISHNA RAO. at Karachi. reg^'^ns du golfe du Tonkin. Ann. de Phys. India Met. Det)t., Sci. Notes, v. 7, no. 75, 75-101, 1938. du Globe, no. 17, pp. 129-133, 1936. pp. DE.TORGIO. W. A., and otlievg. Weaiher tynes RODEWALD. M.. Batumer Starkregen, Ann. d. Hydr., 1937, H. 9. p. 433. of Central Asia. 3. Go'^phys., Moscow, v. 5, no. 2, pp. 200-220, 1935. RODEWALD, M., Bemerkungen zu: Karl Wien. Die Wetterverh^'ltnisse Nanqa DESAI, B. N., and S. Mai, A discussion of am sorne^ aeroplane ascents at Drigh Rnad (Ka- Parbat wdhrend der Kat'^strophe auf der rachi) on dmis of duststor^ns- thunderstorms deutschen Hi-âlaia-Eor.nedition 19 Si, M. Z., and dust raising winds, India Met. Dept., Bd. 53. pp. 182-186. 1936. S-i. Notes. V. 8. no. 87, pp. 31-45, 1940. SEENIVASAIAH. B. N., and N. K. Sur. A EOCHLER-HMTKE, G-. Monsune. Depressio- studi) of the duststorms of Agra. India Met. Memoivci. 1. nen und Taifune Sudchinas. Gerl. Beitr. Dent., v. 27. nt. 29 pp., 1939. Geophys., v. 61, 1935, pp. 233-244. Corriment by Veryard, Met. Mag., June, 1938, p. 112-6. DESAI, B. N.. and S. Mai. Thundersqualls of The distribution temperature Bengal. Gerl. Beitr. Geophys., Bd. 53, pp. SUR, N. K., of 285-304, 1938. in the upper levels of a depression originating in the Bay nf Beng-^l during the In- rUTI, H., On dust-storms in. China and Man- di'-'n s'ûthwest monsoon, India Met. Dept., choukuo. J. Met. Sc.. Japan, v. 17. no. 12. Sci. Notes, V. 6, no. 62, pp. 53 56, 1935. pn. 473-486, 1939. [Abst. in English, pp. 45-46.] SUR, N. K., The thermal structure of the unper air over a (?p"ress!'"n dur^na the In- FUTI, H., and others. On the structure of on dian south-west monsoon. Ind'n Mot. Dont.. extratropical cyclone in the Far East. J. Sci. Notes, V. 6, no. 65, pr.. 113-120, 1935. Met. Soc .Tapan, v. 17, pn. 343-355 (Sum- mary in Eng. p. (33) ), 1939. TAKAHASI. K., and H. Sakata, On some methods rtredicti-ng the pa*'^ and velocity of GOLMAN, S., Si'nopt.irai conditions o^ snti+h a tv^^hnnn. .T. Met. S'^". Japan, v 17. T)p. cyclone inru.sh into the territory of Kazakh- 422-425 [summary in Eng. p. (42)]. 1939. stan and West Siberia, du'î^n the su~nm.er half year. Moscow, Met. Hydrol., 1939, no. TU. C.-W.. A note on the constitution of ty- 1, pp. 36-46. phoons. BAMS, V. 20, pp. 117-119. 1939. )

BIBLIOGRAPHY 219

VENKITESHWARAN, S. P., Rainfall due to YAO, C.-S., The stationary cold fronts of winter disturbances and the associated upper central China and the wave-disturbances developed over the lake-basin, China, Nat. air temperatures over Agra, Proc. Nat. Inst. Res. Inst. Met., Memoir, v. 13, no. 1, 17 pp., of Sci. of India, v. 5, no. 1, pp. 117-122, maps, 1939. In German: Das Wetter 1939, 1939. p. 213-8.

7. Africa (North of the Equator)

BROOKS, C. E. P. and Durst, C. S., The Cir- ''ue Occidental Frangaise, Serie B, no. 3 culation of air by day and night during 1937, 93 p. the south-west monsoon near Berbera, Soma- FROLOV, S., Les variations de la pression en liland, v. 61, no. 259, 167-177, QJRMS, pp. A. O. F. en mai 19Si, Annal. du Phys. du April, 1935. (see also: Prof. Notes, Met. Globe, no. 14, pp. 45-50 and pp. 57-58, 1936. Off. Lond., No. 65, 1934). HUBERT, H., Les Masses d'Air Quest Afri- DAKING, C. G., The Meteorology of Ka- W. caine, Annal. de Phys. du Globe, no. 26, pp. maran Island (Red Sea), QJRMS, v. 58, no. 33-64 [valuable paper.] 247, pp. 441-447, 1932. de HYS, Ion west African meteorology^, Microbarograph oscillations. DURWARD, J., Annal. de Phys. du Globe, no. 15, pp. 65-68. Met. Mag., May 1934, p. 45-8. HUBERT, H., Nouvelles Etudes de la Meteoro- DURWARD, J., Pressure, temperature and logie de I'Afrigue Occidentale Francaise. wind variations at Heliopolis, Egypt, asso- Paris, 1926, 198 pp. ; Nouvelles Recherches ciated with the warm, and cold sectors of a sur les Grains Orageux et les Pliues en depression. Met. Mag., v. 63, April, 1928, Afrique Occidentale, Paris, 1922, 42 pp. pp. 57-61. H., Origine africaine d'un cyclone DURWARD, J., Upper winds at Wadi Haifa HUBERT, (Sudan), Met. Off. Lond. Prof. Notes, no. tropical atlantique [New England Hurri- cane], Annates de Physique du Globe de 72, 1936, 12 pp. France d'Outre-Mer, no. 34, pp. 97-116, DURWARD, J., Weather changes on the West 1939. African air route. Met. Mag., Nov., 1936, pp. 227-229. HUBERT, H., Sur V allure des surfaces de dis- continuite dans le cas de fronts froids en ELFANDY, M. G., The formation of depres- afrique occidentale francais, Proces Ver- sions of the Khamsin type. QJRMS, v. 66, baux des Seances de la Sect, de Met., 4th pp. 323-335, 1940. Assembly Int. Union Geod. and Geophys., FAILLETTAZ, R., La radiation solaire et le Stockholm, Fasc. 2, p. 152, Paris, 1933. trouble atmospherigue a Tamanrasset (Hog- INT. MET. ORGANIZATION, Secretariat, gar), These, Univ. Paris, 1987. ; also Mem. Regional Commission No. I Africa, Minutes Off. Nat. Met. de France, no. 26, 1938, 75 of the first meeting Lusaka, Aug. 1936. Publ. pp. (radiosoundings and upper winds). No. 32, Secret. IMO, Utrecht, 1937, 126 pp. FARQUHARSON, J. S., The diurnal variation JURY, A., et G. Dedebant, Les types de temps of wind over tropical Africa, QJRMS, v. au Maroc, France, OfRce Nat. Met., Mem- 65, no. 280, pp. 165-184, 1939. orial, no. 18, 44 pp., 1925. FLOWER, W. D., An analysis of the cold MORSELLING, N. A., L'evoluzione del tem- front over Egypt on March 7, 1929, QJRMS, po nelV Africa Orientale Italiana, Rivista di V. 57, no. 240, pp. 275-287, 1931. Meteorologia aeronautica. An. 3, pp. 12-28, 1989. FLOWER, W. D., A note on the influx of cold air into Egypt and N. Sudan lS-23 PETITJEAN, L., La frontologie en Afrique April 1930, QJRMS, v. 66, 1940, p. 216-222. du Nord. Beitr. z. Phys. d. Atm., Bd. 19, FLOWER, W. D., Minor haboob at Ismaila, pp. 163-172, 1932. Egypt, Met. Mag., v. 71, 1986, pp. 111-114. PICQ, [On upper air at Djibouti'] Annal. de FLOWER, W. D., Temperature and relative Phys. du Globe, no. 16, pp. 100-101, 109-111. humidity in the atmosphere over lower H., und Torna- Egypt, Met. Off. Lond. Prof. Notes, no. 75, REGULA, Drucksehwankungen Ann. d. 11 pp. (bibliog. does an der Westkuste von Afrika, Hydrog., v. 64, pp. 107-111, 1936. FOISSY, A., and others. Etudes Met. sur I'A- frique Occidental Francaise, Pub. du comite WALTER, A., Annual Report, British East d'etudes historiques et scientifiques de I'Afri- Africa Met. Service, 1938, 40 p. H. METEOROLOGY OF THE FRICTION LAYER Turbulence

AKERBLOM, F., Sur les courants plus bas BOSSOLASCO, M., Sulla struttura del vento dans I'atmosphere, Nova Acta Reg. Soc. Sc. al suolo nella regione di Mogadiscio, Publ. Upsal. Serie 4. v. 2, No. 2, 1908. (See no. 14, Particip. Ital. all'Anno Polare In- also Exner, Ann. d. Hyd., 1912, p. 226-239.) tern. 1932-3, Staz. Geofis. di Mogadiscio. Torino, 1936, 17 pp. (bibliog.) (also see ALI, B., The wind at Agra and its structure, Beitr. Phys. fr. Atmos., v. 28, 1935, pp. Mem. India Met. Dept., v. pt. 1930. 25, 6, 16-23.) BAMFORD, A. J., Vertical air currents as measured by pilot balloons, QJRMS, v. 55, BiJTTNER, K., Die Warmeubertragung durch no. 232, pp. 363-384, 1929. Leitung und Konvektion, Verdunstung und BECKER, R., Untersuchungen iiber die Fein- Strahlung in Bioklimatologie und Meteorolo- struktur des Windes, M. Z., Bd. 47, 1980, gie, Veroff. Pr. Meteor. Inst., Abh. v. 10, pp. 183-184. No. 5, Berlin, 1934. BEST, A. C, Transfer of heat and mom,entum in the lowest layers of the atmosphere, Lon- CORWIN, E. F., The tail method of obtaining don, Met. Office, Geophys. Memoirs, no. 65 data on winds aloft, BAMS, v. 21, pp. 184- (v. 7), pp. 5-66, 1935. 189, 1940. 220 AIR MASS ANALYSIS

DURST, C. S., Notes on the variations in the REGULA, H., Geschwindigkeitsverteilung in structure of wind over different surfaces, Warm- und Kaltluftstromungen iiber See, QJRMS, V. 59, no. 252, p. 361, Oct., 1933. Ann. d. Hydr., 1939, H. 6, pp. 310-314. DURWARD, J., Bumpiness on the Cairo- THE RELATION of bumpiness to lapse of Basra air route, London, Met. Office, Prof. temperature at El Khanta, near Cairo from Notes, no. 52 (v. 4), pp. 2-6, 1929. July 27th to August 3rd, 1920, London, Met. ERDBRiJGGER, W., et al, Untersuchung ther- Office, Prof. Notes no. 20, pp. 118-121, 1921. mischer Vertikalbegungen uber der Ebene RICHARDSON, L. F., Atmopheric diffusion mittels Segelflugzeug, Beitr. z. Phys. der shown on a distance-neighbor graph, Roy. fr. At., Bd. 21, pp. 169-192, 1934. Soc, Proc, V. 110, pp. 709-737, 1926.

FeRIET, J. K. de : La turbulence du vent dans RICHARDSON, L. F., Some measurements of les couches inferieurs de I'atmosphere, Lou- atmospheric turbidence, Phil. Trans, of the vain, Rev. de Quest. Sci., v. 27, 1935, pp. Roy. Soc, London, Ser. A, v. 221, 1920. 18-58, bibliog. ROSSBY, C.-G., A generalization of the the- GEIGER, R., Miroklimatologische Beschreibung ory of the mixing length with applications der Wdrmeschichtunq am Boden, M. Z., Oct. to atmospheric and oceanic turbidence, Mass.

1936, pp. 357-360 ; ibid. Apr. 1937, pp. 133- Inst, of Tech., and Woods Hole Ocean- 138; ibid. Aug. 1937, pp. 278-284. ographic Inst., Papers in Met. and Phys. GIBLETT, M. A., The structure of wind over Oceanogr., v. 1, no. 4, 36 p., 1932. level country, London, Met. Office, Geophys. ROSSBY, C.-G., The vertical distribution of Memoirs, no. 54 (v. 6), pp. 7-119, 1932. atmospheric eddy energy M. W. R., v. 54, HAUDE, W., Temperatur und Austausch der no. S, 1926, pp. 321-332. bodcnnahen Luft Uber einer Wiiste, Beitrage ROSSBY, C.-G., & R. R. Montgomery, The z. Phys. d. fr. At., Bd. 21, pp. 129-142, 1934. layer of frictional influence in wind and HAURWITZ, B., Rossby on turbulent motion ocean currents, M. I. T., & Woods Hole Inst., in the atmosphere, BAMS, v. 18, pp. 142-4, Oceanogr. Papers in Meteorology and 1937. Phys. Oceanogr., V. 3, No. 3, 1935. HELLMANN, G., Uber die Bewegung der Luft SCHELL, I. I., On the vertical distribution of in den untersten Schichten der Atmosphare, wind velocity over mountain summits, (4 .papers), Sitz. Ber. Preuss. Akad. Wiss., BAMS, V. 17, pp. 295-300, 1936.

1915, 1917, 1919 ; MZ, v. 32, 1915, p. 1. SCHMIDT, W., Der Massenaustausch in freier und HEYWOOD, G. S. P., Wind structure near the Luft verwandte Erscheinungen, Ham- 1925. ground and its relation to temperature gra- burg, dient, QJRMS, V. 57, no. 242, pp. 433-455, SCHMIDT, W., Die Struktur des Windes, Sitz.- 1931. Ber. d. Akad. d. Wiss. Wien, Bd. 138, pp. 85 ff., 1929. H6HNDORF, F., Die Lvjtstromung in der oberrheinischen Tiefebene bei westlichen SCHMIDT, W., Stromungsforschuna in freier Winden, Beitr. z. Phys. d. fr. Atm., Bd. 14, Luft, M. Z., Bd. 46, 1929, pp. 495-504. pp. 198-214, 1928. (other similar papers by SCHMIDT, W., Turbulence near the ground, Hohndorf appear in later volumes of this London. R. Aero. Soc, J., v. 39, pp. 355- journal.) 368, 1935. HoHNDORF, F., und R. Marquardt, Ther- SEILKOPF, H., Mittelrdumige atmosphdrische mische Vertikalbewegungen nach Schwebel- Stromungstypen, Ann. d. Hydr., Zweites balloon-Vermessungen, Beitrage z. Phys. d. Koppen-Heft, Beiheft zur September-Num- fr. At., Bd. 21, pp. 147-168, 1934. mer 1936, pp. 79-87. IDRAC, P., Etude sur les conditions d'ascen- SHERLOCK, R. H., and M. B. Stout, Wind dance du vent favorable au vol a voile, structure in winter storms, J. Aero. Sci., France, Office Nat. Met., Memorial no. 7, V. 5, pp. 53-61, 1937. 33 pp., 1923. SUTCLIFFE, R. C, Surface resistance in at- KIDSON, C. I., Model experiments on the site mospheric flow, QJRMS, V. 62, no. 263, pp. of Rongotai Aerodrome, Roy. Aero. Sec, J., 3-14. 1936. V. 42, pp. 165-172, 1938. SVERDRUP, H. U.. The eddy conductivity of KIDSON, E., and Treloar, The rate of ascent the air over a smooth snow Held, Geofys. pilot balloons of at Melbourne, QJRMS, Pub., V. 11, no. 7, pp. 5-69, 1936. (See also 1929, pp. 153-168. "Sverdrup," ref. under Sect. C, above.) KUETHE, A. M., Some features of atmos- TAIT, G. W. C, Diurnal pressure differences / pheric turbulence and the passage of fronts, in regions of high pressure, BAMS, v. 21, ^ Daniel Guggenheim Airship Institute, Pub. pp. 39-43, 1940.

No. 2, 1935, pp. 71-79 ; further report, id. TAYLOR, G. I., Meteorological section in : Ice Publ. No. 3, 1935, 117-124. pp. observation, meteorology, and oceanography. LETTAU, H., Weiterfiihj-ung der Freiballon- Report on the work carried out by the "S, Untersuchungen iiber effektiven Vertikal- S. Scotia" 1913, London, 1914, pp. 48-68. austausch und Luftmassen- Alterung mit Anwcnduna auf die Frage der Land-Verdun- TAYLOR, G. I., Skin friction of the wind on stung, M. Z., Nov. 1937, pp. 406-412. the earth's surface, Proc. Roy. Soc, A, v. MAAS, W., Neuere Untersuchungen iiber die 92, no. A637, 1916. gleitende Reibung an der Erdoberfldche, Dis- THOMPSON, F. L., and others. Air condi- sertation, Leipzig, Univ., 1935, 33 pp. ; tions close to the ground and the effect on MORGANS, W. R., Relation between ground ' airplane landings, U. S. National Advisory contours, atmospheric turbulence, wind ' Com. for Aero., 20th Ann. Rep., No. 489, s'^eed and direction. Research Mem., no. pp. 271-283, 1934. 1456, Aeron. Res. Comm., London, 1932. ULANOV, H., The change of the velocity of MiJLLER, F., Storung der Windstromung und wind with heiaht above the sea. Bull. Acad. des Austausches iiber einem Gebailde, Zeit- Sci. URSS, CI. Math. Nat.. Ser. Geogr.- schr. Geophys., Bd. 12, pp. 173 ff., 1936. Geophys., v. 1939, no. 3, p. 313-4. PAESCHKE. W., Experimentelle Unfersuchun- gen zum Rauhigkeits-und Stabilitdtsproblem WAGNER, A., ijber die Tageswinde in der in der bodennahen Luftschicht, Beitr. z. freien Atmosphdre, Beitr. zur Phys. fr. At., Phys. d. fr. Atm., Bd. 24, pp. 163-189, 1938. V. 25, pp. 145-170, 1938. [Data from U. S.] BIBLIOGRAPHY 221

2. Surface Temperature Influences

ALBRECHT, F., ijber den Zusamenhang zwi- senen Ebene, Wiss. Abh. d. RfW, Bd. 3, p. schen taglichen Temperaturgang und Strah- 10, Berlin, 1937. lungshaushalt, Gerl. Beitr. Geophys., v. 25, NIEDERDORFER, Messungen des Wdrmeum- pp. 1-12. satzes ilber schneebedecktem Boden, MZ, Bd. ANGSTROM, A., The albedo of various sur- 50, pp. 201, ff, 1933. faces of ground, Geog. Ann., 1925, h. 4, p. RAMAN, P. K., The measurement of the 323 S. transmission of heat by convection from insolated BLANC, M. et al. Papers on Fruit-frost ground to the atmosphere, Proc. Indian studies in Florida, BAMS, v. 21, 1940, pp. Acad. Sci., v. 3, no. 2, pp. 98-106, 65-70. 1936. BROOKS, C. F., Oceanography and Meteor- ROBITZSCH, M., Ground surface temperature as ology, Ch. 14, pp. 457-519, with bibl., in dependent on insolation and as control- Physics of the Earth— V. Oceanography. ling diurnxil temperature unrest and gusti- Nat. Res. Counc, Washington, 1932. ness, M. W. R., v. 51, pp. 406-407, 1923. FALCKENBERG, G. und E. Stoecker, Boden- 'SCHUBERT, J., Grundlagen der allgemeinen inversion und atmosphdrische Energieleitung und forstlichen Klimakunde. I., Die Son- durch Strahlung, Beitr. z. Phys. d. fr. Attn., nenstrahlung und der Wdrmeumsatz an der Bodenoberfldche. II. Die Bodenwarme, Zeit. Bd. 13, p. 246 flf., 1927. Forst.—und Jagdw., Berlin, Bd. 62, pp. 689- FITTON, E. M., and C. F. Brooks, Soil tem- 705, 1930 : Bd. 64, pp. 715-734, 1932. peratures in the United States, M. W. R., V. 59, pp. 6-16, 1931. SCHUBERT, J., Das Verhalten des Bodens gegen Wdrme, in Blanck, Handbuch der Bo- GEORGE, J. J., On the distortion of stream denlehre, Bd. 6, pp. 342-375, Berlin, 1930. fields by small heat sources, M. W. R., v. 68, pp. 63-66, 1940. SLOCUM, G., The no'rnal temperature distribu-' tion of the surface water of the western HERR, L., Bodentemperaturen unter besonde- North Atlantic Ocean, M. W. R., v. 66, pp. rer BerUckichtigung der dusseren meteorolo- 39-43, 1938. gischen Faktoren, Berlin, 1936, 63 pp. (Diss. Leipzig, 1936.) TAKAHASI, Y., Sea currents and weather in Japan, J. Met. Soc. Japan, v. 18, no. 5, pp. N. K., and E. L. Davies, JOHNSON, Some 149 [Eng. Abstract on page (17)], 1940. measurements of temperatures near the sur- B. face in various kinds of soils, QJRMS, v. 53, THORNTHWAITE, C. W., and Holzman, no. 221, pp. 45-58, 1927. The determination of evaporation from, land and water surfaces, M. W. R., v. 67, pp. KERaNEN, J., Wdrme und Temperaturverhalt- 4-10, 1939. nisse d. Obersten Bodenschiehtung, in Nip- poldt et al, Einfuhrung in die Geophysik, WEIGHTMAN, R. H., Snow cover in southern Bd. 2, Berlin, 1929, 388 pp. Canada as related to temperatures in the KRuGLER, J. Ndchtliche Wdrmehaushaltsmes- North Atlantic States and the Lake Region, sungen an der Oberfldche einer grasbewach- M. W. R., V. 59, pp. 383-386, 1931.

3. Mountain Meteorology

ARAKAWA, H., The effect of topography on COULTER, J. W., Meteorological reports of the direction and velocity of wind. Geophys. the Mauna Kea Expedition, 1935 (Part 1) :

Mag., Tokyo, v. 5, no. 1, pp. 63-68 ; v. 7, The mean temperature on Mauna Kea and no. 1, pp. 9-18, 1932, 1933; v. 11, p. 488-91; in the free air, BAMS, v. 19, pp. 349-351, also Futi, V. 11, No. 11, p. 492-5. 1938. 'ARAKAWA, H., On the influence of topo- CROSSLEY, A. F., Note on the variation of graphy on the microbarometric oscillations, presstire accompanying a distortion of air Geophys. Mag., Tokyo, v. 5, no. 3, pp. 223- flow, QJRMS, V. 64, no. 276, pp. 477-481, 236, 1932. July, 1938. BALDIT, A., Meteorologie du Belief Terrestre, DbDeBANT, G., a. Baldit, J. Gilbert, La cam- Paris, Gauthier-V., 1929. pagne aerologique 1935 a Banne d'Ordanche, La Meteorologie, v. 12, pp. 111-144, 1936. BALDIT, A., Les perturbations dues au relief terrestre et I'aviation, La Meteorologie, DEFANT, A., Die Windverhdltnisse im Ge- juin, 1935, no. 123, pp. 267-312. biete der ehemaligen oesterr. —Ungar. Mo- narchic, Jahrb. Zentr.-Aust. Met. Geodyn., BAUMANN, G., Stromungseinfluss des mittel- Anhang 1920. Vienna, 1924. deutschen Gebirgsrandes und seine Bedeu- tung fiir die Flugmeteorologie dieses Geb- EKHART, E., Neuere Untersuchungen zur ietes, Aus d. Arch. d. Deutsch. Seewarte, Aerologie der Talwinde: Die periodischen Bd. 49, Nr. 9, 48 pp., 1931. Tageswinde in einem Quertale der Alpen, Beitrage z. Phys. d. fr. Atmos., Bd. 21, pp. BRUECKMANN, W. Beispiele der Gestalt des 24.5-268, 1934. Stromfeldes der Luft in der Schweiz, Ann. d. EREDIA, F., Di una singolarita aerologica Schweiz. Met. Anstalt, No. lb, 1928, Anhang della costa tirrenica della Calabria, La Met. 5 p. Prat., Ann. 17, no. 2, pp. 49-57. BuDEL, A., Zugspitze bahn Versuche, Pt. 1 in ERTEL, H., Turbulenz und Druckerniedrigung Deut. Met. Jahrbuch Bayern, 1929, Pt. 2, auf Bergstationen, MZ, Bd. 49, pp. 199 ff, 1930, Pt. 3, 1931. [remarkable study of 306 ff., 1932. aerology of a large-mountain slope]. FERGUSSON, S. P., The value of high-level BURGER, A., and E. Ekhart, iJber die Tagliche data in forecasting changes of temperature— Zirkulation der Atmosphdre in Bereiche der A contribution to the meteorology of Mount Alpen. Gerl. Beitr. Geophys., Bd. 49, pp. Rose, Nevada, Nevada Univ, Tech. Bull. 341-367, 1937. 83, 1915, 30 pp. CHURCH, P. E., A zone of stagnation be- FERGUSSON. S. P., Aerological studies on tween gorge and gradient wind in British Mount Washington, Trans. Amer. Geophys. Columbia fjords, BAMS, Oct. 1938, pp. 344-5. Union, 1934, pt. 1, pp. 114-117. ; )

222 AIR MASS ANALYSIS

FeRIET, J. de, Atmosphdrische Stromungen WeUensegelflUgen und Beobachtungen an Wolkenstudien nach Kinoaufnahmen im der Moazagotl-Wolke, Beitr. z. Phys. d. fr. Hochgebirge (Jungfrau und Matterhorn), Atm., Bd. 25, pp. 251-299, 1939. MZ, Bd. 53, pp. 277-ff, 1936. LANGE, K. O., iJber Windstromungen an FICKER, H. von, Bermerkungen iiber den HUgelhindernissen, Rhon - Rossitten - Gesell- Verlauf von Stromlinien im Gebirge, VeroflE. schaft e. V., Forschungs-Inst., Veroff., no. 4, d. Preuss. Met. Inst., Berlin, no. 327, pp. C. Abh., 1931, 29 pp. 31-46, 1925. LEE, J., Dynamical effect of eastern Chinese FICKER, H. von, Der Einfluss der Alpen auf coastal winds and its influence upon the Fallgebiete des Luftdruckes, M. Z., Bd. 37, temj>erature, China, Nat. Res. Inst. Met., pp. 350-363, 1920. (Abstr. MWR, 1921, p. Memoirs, v. 12, no. 1, 45 pp., 1938. 510.) RAINE, C. T., Meteorological reports of the FICKER, H. von, Der Vorstoss kalter Luft- Mauna Kea Expedition, 1935 (Part 2) : massen nach Teneriffa, Berlin, Preuss. Met. Meteorological observations at Lake Waiau, Inst., Abhandlungen, Bd. 8, no. 5, pp. 3-34, Aug. 8-19, 1935, BAMS, v. 20, pp. 97-103, 1926. 1939 FIELD, J. H., and R. "Warden, A survey of REINHARDT, H., Ein Beitrag zum Problem the air currents in the Bay of Gibraltar, der hohen Hinderniswolken, Beitr. z. Phys. 1929-30, London, Met. Office, Geophys. Mem., d. fr. At., Bd. 26, H. 1, pp. 23-37, 1939. no. 59 (v. 7), pp. 3-30, 1933. ROSCHKOTT, A., Der Wind auf Berggipfeln GEORGII, W., Die Luftstromung iiber Gebir- und in der freien Atmosphdre : Verallgemei- gen, M. Z., Bd. 40, pp. 108-112, 1923. nerte Windrosen fUr die freie Atmosphdre, HARTMANN, W., Vsber ein Niederschlags- M. Z., Bd. 51, pp. 374-377, 1934. gebiet geringer vertikaler Mdchtigkeit im SCHELL, I. I., Differences between tempera- mitteldeutsehen Bergland, Deutsch. Flug- tures, humidities, and winds on the White wetterdienst, Erfahrungsberichte, Sonder- Mountains and in the free air. Trans. Anaer. band 3, pp. 119-124, 1930. Geophys. Union, 1934, pt. 1, pp. 118-124. HESSELBERG, Th., anf H. V. Sverdrup, SCHELL, I. I., Free-air temperatures from ijber den Einfluss der Gebirge auf die Luft- observations on mountain peaks with appli- bewegung Idngs der Erdoberfldche, Veroff. cation to Mt. Washington, Trans. Amer. Geophys. Inst. Univ. Leipzig, 2nd Ser., Bd. Geophys. Union, 1935, pt. 1, pp. 126-141. 1, H. 4, pp. 101-116, 1914. SCHMAUSS, A., Verhalten der relativen HOFFROGGE, Chr., Experimentelle Unter- Feuchtigkeit auf der Zugspitze, Deut. Met. suchungen der bodennahen Luftstromungen Jahrbuch Bayern Appd. C, pp. 5-19, 1933. am Hang und in ebenen Geldnde, Zeit. f. SEILKOPF, H., Meteorologische Flugerfah- Geophysik., Js. 15, h. 3-4, pp. 184-213, 1939. rungen im nordwestlichen Deutschland, Ann. JELINEK, A., Untersuchung periodischer Ta- d. Hyd., 1926, pp. 75-84, 1927, April no. geswinde in Siidtirol, Beitrage z. Phys. d. (cont. ). fr. Atmos., Bd. 21, pp. 223-244, 1934. STONE, R. G., The history of mountain me- KOCHANSKI, A., Notice concernant les cou- teorology in the United States and the rants axcendants observes sur le terrain diJt Mount Washington Observatory, Trans. vol a voile de Bezmiechowa, Lwow, Geophys. Amer. Geophys. Union, 1934, pp. 124-133. Inst. Univ., Komunikaty, Tom 6, nr. 69, pp. [with extensive bibliography.] 81-119, 1933. TAYLOR, G. F., The influence of topography KOCHANSKI, A., Vols a voile nocturnes d, on weather forecasting at Salt Lake City, Bezmiechowa, Lwow, Geophys. Inst. Univ., Utah, J. Aero. Sci. Nov., 1939, pp. 18-21. Komunikaty, Tom 8, nr. 97, pp. 77-113, WAGNER, A., Neue Theorie des Berg- und 1936. Talwindes, MZ, Bd. 49, pp. 329-341, 1932. KuTTNER, J., Moazagotl und Fohnwelle, (bibliog. Beitr. z. Phys. d. fr. At., Bd. 25, H. 2, pp. WAGNER, A., Der tdgliche Luftdruck- und 79-115, 1938. Temperaturgang in der freien Atmosphdre KuTTNER, Joachim, Zur Entsteheung der und in Gebirgstdllern, Gerl. Beitr. Geophys, Fohnwelle: Untersuchung auf Grund von Bd. 37, pp. 315-344, 1932.

4. Micro-Aerological Analysis and MicrocHmatology

BROOKS, F. A., Engineering factors in- FRITZCHE, G., und R. Stange, Vertikaler volved in orchard heating, Mech. Eng., Tem,peraturverlauf iiber einer Grosstadt, Sept., 1938, pp. 677-681. [inversions and ra- Beitr. z. Phys. d. fr. Atm., Bd. 23, pp. 95- diation.] 110, 1936. CHURCH, P. E., Surface details of a warm GEIGER, R., Beispiel eines Luftkorperkampfes front in the Strait of Juan de Fuca, BAMS, in seiner Abhdngigkeit von der Geldndeges- V. 19, pp. 400-402, 1938. taltung. Beit. Phys. fr. At., Bd. 16, H. 1, CORNFORD, C. E., Katabatic winds and the pp. 57-75, 1929. prevention of frost damage, QJRMS, v. 64, GEIGER, R., Das Klima der bodennahen Luft- no. 277, pp. 553-592, Oct., 1938. schicht. Braunschweig, 1927. [bibliog.] DYKE, R. A., Nocturnal temperature inver- (Later treatise in Koppen-Geiger "Hand- sions near the Gulf Coast, M. W. R., v. 57, buch der KJimatologie," v. I, Teil D, 1930, pp. 500-502, 1929. 47 pp.) FLOWER, W. D., An investigation into the GEIGER, R., iiber einen lokalen Kdlteeinbruch variation of the lapse rate of temperature in Miinchen und seine Ursachen, Deut. Met. in the atmosphere near the ground at Ismai- Jahrbuch Bayern. App. B, 4 p., 1933. lia, Egypt, London, Met. Office, Geophys. GEIGER, R.. M. Woelfle, and L. Ph. Seip, Memoirs, no. 71 (v. 8), pp. 5-87, 1937. Hohenlage und Spdtfrostgefdhrdung, (I-VII

FRANSSILA, M., Mikroklimatische Unter- Mitt. ) , Forstwissenschaftliches Centralblatt, suchungen des Wdrmehaushaltes, Helsinki, H. 17, 1933, pp. 579-592, H. 21, 1933, pp. Mitt. d. Met. Zentralanstalt, No. 20, 1936. 737-746, H. 5, 1934, pp. 141-151, H. 7, 1934, ) )

BIBLIOGRAPHY 223

pp. 221-230, H. 8, 1934, pp. 253-260, H. 11, vapour near the earth's surface, Tokyo, 1934, pp. 357-364, H. 14, 1934, pp. 465-484. Univ., J. Fac. So:., v. 1, Sec. 1, pp. 339- 347, 1927. GRUNOW, J., Der Luftaustausch in der Grosstadt, Zeit. d. Ver. deut. Ingenieure, Bd. MONTGOMERY, R. B., Observations of verti- 80, pp. 70-72, 1936. cal humidity distribution above the ocean surface their relation evaporation, HALES, W. B., Canyon winds of the Wasatch and to Mass. Inst, of Tech. and Hole Ocean- Mtns., BAMS, v. 14, pp. 194-5. Woods ographic Inst., Papers in Phys. Ocean- B., Microbarometric oscillations HAURWITZ, ography and Met., v. 7, no. 4, 30 pp., Feb., at Blue Hill: Part 1 —Waves of pressure 1940. and wind at the top of a ground inversion, NITZE, F. Ndchtliche BAMS, V. 16, pp. 153-157, 1935. W., Austauschstromun^ gen in der bodennahen Luftschicht, herge- JOHNSON, N. K., A study of the vertical leitet durch Stereophotogrammetrischver- gradient of temperature in the atmosphere messene Bahnen von Schwebeballonen, Zeit. the ground, London, Met. Office, Geo- near Geoph., Bd. 11, pp. 247-271, 1935. (abstr. Memoirs, (v. 5,) no. 46, 3-30, phys. pp. Biokl. Beibl., 3, 125-128. 1936) 1929. PAESCHKE, W., Mikoklimatische Unter- _ KOCH, H. G., Usher Temperatur und Austausch suchungen innerhalb und dicht iiber ver- innerhalb der Bodeninversion, Gerl. Beitr. schiedenartigem Bestand, Bioklim. Beiblatter, Geophys., v. 407-26, 1937. 49, pp. Jg. 4. pp. 155-163, 1937. H. G., Zur Mikroaerologie eines gros- KOCH, PHEIFFER, H., Kleinaerologische Untersuch- seren Waldsees Gerl. Beitr. Geophys., Bd. ungen am Collmberg, Veroff. Geophys. Inst. 44, pp. 112-126, 1935. Univ. Leipzig, Bd. 11, No. 5, pp. 265-306., KOROTKEWITSCH, V. N., Eine ijbersich der 1938. das Mikroklima umfassenden Arbeiten, U. S. PIERCE, L. T., Temperature variations along Central Office of the Hydro-Met. Serv- 5. R., a forested slope in the Bent Creek Experi- ice, Central Geophys. Obsy., Trans. Fasc. raental Forest, N. C, M. W. R., v. 62, pp. 3-46, Leningrad, 1936. (In Russian, 6, pp. 8-13, 1934. with summary in German). (An exhaustive RAMDAS, L. A., The variation with height of review ; bibliog. the water vapor content of the air layers H., und Besehrei- KOSCHMIEDER, Nachweis near the ground at Poona, Bioklimatische bung sowie Beitrdge zur Kinematik und Dy- Beiblatter, Jg. 5, pp. 30-34, 1938. namik des Seewindes, Forschungsarb. d. met. Inst. Danzig, H. 8, 1936, 44 p. ROOT, C. J., Airport and city temperature at Detroit. Mich., M. R., v. 99, 1939 KUHNERT, W., Eine Beohachtung des Tem- W. 67, pp. the subject]. peraturgradienten beim Auftreten von Strah- [with bibliog. of lungsnebel; die Entwicklung der Bodenin- R6TSCHKE, M., Untersuchungen iiber die version, Beitr. z. Phys. d. fr. Atm., Bd. 18, Meteorologie der Staubatmosphdre, Veroff. pp. 219-224, 1932. Geophys. Inst. Univ. Leipzig, Bd. 11, no. 1, 78 1937. MADE, A., Messungen mit Widerstandsther- pp., mometern an Funkturmen Beitrage z. Phys. SELTZER, P., Etudes micrometeorologiques en d. fr. Atmos., Bd. 21, pp. 309-312, 1934. Alsace, Ann. de I'lnst. de Phys. du Globe, MATH, F. A., Battle of the Chinook Wind at Strasbourg, 1934, Annexe. 57 pp. (Also sep. Havre, Mont., M. "W. R., v. 62, pp. 54-57, as Theses, Univ. Strasbourg, 1935. 1934. STEINHAUSER, F., Neue Untersuchungen MATUI, H., Atmospheric impurities in the der Temperatur-verhdlt^iisse von Grossstdd- central part of Tokyo. J. Met. Soc. Japan, ten; Methode und Ergebnisse, Bioklim. v. 17, pp. 367-372 [Summary in Eng. p. Beibl., Bd. 1, pp. 105-111, 1934. (34)], 1939. WiJST, G., Temperatur- und Dampfdruckge- MINAMI, T. and Y. Hukumoto. On the fdlle in den unfersten Metern iiber der Meer- distribution of the mixing ratio of aqueous esoberfldche, MZ, Bd. 54, pp. 4-9, 1937.

I. PRECIPITATION AND CONDENSATION; CONVECTION; CLOUDS; STRATUS AND FOG

ABE, C, Distribution and movement of clouds BERG, H., iiber ndchtliche Hochneheleinhriiche around Mt. Fuji, Tokyo, Central Met. Obsy., vor dem mitteldeutschen Berg^and bei Nord- 466 pp., 1937. weststromung, Erfahrungsberiohte des Deut- schen Flugwetterdienstes, 8. Folge, Nummer ANDERSON, J. B., Observations from air- 61-78. 1933. planes of cloud and fog conditions along 7, pp. southern California coast, M. W. R., v. 59, BERG, H., Wolken schichtung und Wolkenstruk- pp. 264-270, 1931. tur, Berlin. Reichsamt fur Wet+erdienst, ARAKAWA., H.. Zur bildung der Cunb Wolken "Wissenschaftliche Abhandlungen, Bd. 3, Nr. in der Kaltluftmassen und zur Bildung und 8, pp. 1-33, 1937. inbesondere ErhaHung des Nebels in der BERGERON, T.. (Lectures on clouds). Moscow Jn. Met. Soc. Jap., v. 18, Warmluftmasse. Centr. Hydro-Met. Comm., 1934. [In Rus- no. 1940, p. (also Takahasi, Transfor- 3, (7) sian only.] mation of cold and dry air by traveling over cloudy and warm sea, id., p. (7) ) BERGERON, T., On the physics of precimtation. Proves Verbaux de la Seinf-e BENNETT. M. G., Some problems of modern I'U. G. G. I. Lisbonne 1933, Paris 1935. meteornlogy. no. 13—The condensation of de a water in the atmosphere, QJRMS, v. 60, no. BJERKNES, J., Saturated adinhafic ascent 253. pp. 3-14, 1934. or air through drn-ndiabatically descending v. 64, pp. 325-330, BERG. H.. Mam/matusbildungen, M. Z., v. 55, environment, QJRMS, pp. 283-287, 1938. 1938. BERG, H., Stromung und Zustandsverteilung BOWIE, E. H., The summer nighttime clouds eines Instabilitutsschauers, Ann. d. Hydrog. of the Santa Clara Valley, Calif., M. W. R., 1938, pp. 565-569. V. 61, pp. 40-41, 1933. :

224 AIR MASS ANALYSIS

BROCKAMP, B., Beobachtungen von Auf- FINDEISEN, W., Das Verdampfen der Wol- gleitwolken in Gronland, MZ, Bd. 53, pp. ken- und Regentropfen, MZ, Bd. 56, pp. 427-430, 1936. 453-460, 1939. BROOKS, C. F., A Cloud cross-section of a FINDEISEN, W., Zur Frage der Regentrop- winter cyclone, MWR, v. 48, 1920, pp. 26-28. fenbildung in reinen Wasserwolken, MZ, Bd. BROOKS, C- F., Types of mammato-cumulus 56, pp. 365-368, 1939. clouds, MWR, 4, 47, 1919, pp. 398-400. FINDEISEN, W., W. Peppier, and T. Berge- ron, BYERS, H. R., Summer sea. fogs of the cen- Outline of physics of the clouds, BAMS, tral California coast, Univ. Calif. Pub. V. 20, pp. 235-247, 1939. Geogr., V. 3, no. 5, 1930. FUCHS, O., Bodenwasser und therinische Kon- vektion, Beitr. Phys. fr. CADEZ, M., Spielt die Verdamx/fungswdrme Atmos., v. 29, 1933, 175 ff. eine Rolle bei der Zyklogenese? MZ, Bd. 56, pp. pp. 271-272, 1939. FULKS, J. R., Rates of precipitation from, adiabatically ascending air, CADEZ, M., ijber den Einfluss des Schmelzens M. W. B., v. 63, 291-294, 1935. des fallenden Schnees auf die Temperatur pp. der Atmosphdre, MZ, Bd. 56, pp. 272-273, GEORGE, J. J., Fog, its co.uses and fore- 1939. casting with special reference to Eastern and Southern United States (I), v. CHAMPION, D. L., Night radiation and fog BAMS, 21, pp. 135-148, 11, 261-269, IH, ibid, associated with different types of pressure pp. no. 7, 1940. distribution. Met. Mag., v. 71, 1937, pp. 286- 7; p. 129. GEORGE, J. J., and W. M. Bradley, A semi- quantitative method of forecasting summer CLAPP, P. F., The causes and forecasting of stratus in N. American tropical maritime fogs at Cheyenne, Wyo., BAMS. v. 19, pp. air, M. W. R., v. 65, pp. 43-46, 1937. 66-73, 1938. (With note by R. G. Stone, p. 73.) GEORGII, W., Gliding in convection currents, Nat. Adv. Commn. Aeron., Techn. Mem. no. CLAYTON, H. H., Discussion of the cloud 761, 13 pp., 1935. Also: Eleventh Rhon observations [at Blue Hill Obsy.], Ann. Soaring Flight Contest. NACA Techn. Mem. Astron. Obsy., Harvard College, v. 30, pt. 4, no. 623, 1931 ; and Future Problems Soar- pp. 271-500, 1896. of ing Flight, NACA Techn. Mem., no. 709. CLAYTON, H. H., A study of clouds with 1933. data from kites, Ann. Astron. Obsy. Har- GEORGII, W., Die meteorologischen Grund- vard Collese, V. 63, pt. 2, pp. 170-187, 1911. lagen des Leisttmgs-Segelfluges, in : Hand- COUNTS, R. C, Jr., Winter fogs in the great buch des Segelfluges, Stuttgart, 1938. Valley of California, M. W. R., v. 62, pp. als aerolo- 407-410, 1934. GEORGII, W., Das Segelflugzeug gisches Forschungsmittel, Beitr. Phys. fr. CRAWFORD, M. E., A statistical study of At., Bd. 17, pp. 294-306, 1931. su7nmer stratus over South Texas, M. W. HARTMANN,_ W., Schichtgrenzen- und Wol- R., V. 66, pp. 131-133, 1938. kenbitdung in der freien Atmosphdre, Veroff. DEPPERMANN, C. E., Relative humidity gra- d. Badischen Landeswetterwarte, Nr. 3, Ab- dient and the form of cloud bases, BAMS, handlungen Nr. 2, 1922, 20 p. V. 21, pp. 43-45, 1940. HAURWITZ, B., iJber die Wellenlange von DEPPERMANN, C. E., Some interesting Luftwogen, GerL Beitr. Geophys., Bd. 34, types of Manila clouds, BAMS, v. 21, pp. pp. 213-232, 1931. 45-46, 1940. HEBNER, E., Die Nebelperiode vom 19. bis DOUGLAS, C. K. M., The physical process of 25. Januar 19 32, Deutsch. Flugvyetterdienst, cloud 333- formation, QJRMS, v. 60, pp. Erfahrungsberiehte, Sonderband' 3, pp. 145- 334, 1934. 150, 1930. C. K. M., The problem rainfall, DOUGLAS, of HELLMANN, G., System der Hydrometeore, 143-152, QJRMS, v. 60, pp. 1934. Berlin, Preuss. Met. Inst., Abhandlungen, DUBUK, A. F., About the calculation of the Bd. 5, nr. 2, pp. 5-27, 1915. (Engl, transl., hozizontally stratified wet air full energy of M. W. R., 1916, pp. 385-392; 1917, 13-19). instability, J. of Geophys., Moscow, v. 5, HOLZMAN, B., A note on Bergeron's ice- no. 4, pp. 486-496, 1935. nuclei hypothesis for the formation of rain, EISENLOHR, R., Systematic observations of BAMS, V. 17, pp. 331-333, 1936. local cumuli, NACA Techn. Mem. 709, 1933. HOUGHTON, H. G., Problems connected with ERTEL, H., Die vertikale Liiftbewegung bei the condensation and precipitation processes Starkregen, MZ, Bd. 50, pp. 149-152, 1933. in the atmosphere, BAMS, v. 19, pp. 152- FICKER, H. v., xJ6e7- die Entstabilisierung 159, 1938. eines geschichteten steigenden auf Luftmas- HOUGHTON, H. G., and W. H. Radford, On sensystems. M. Z., Bd. 472-474, 53, pp. 1936. the measurewent of drop size and liquid FINDEISEN, W., Die kolloidmeteorologischen water content in fogs and clouds, Mass. Inst, Vorgflnge bei der Niederschlagsbildung, of Tech. and Woods Hole Oceanographie M. Z., v. 55, pp. 121-133, 1938. (Engl, Inst., Papers in Met. and Phys. Oceanog., v. transl., mimeo. U. S. Wea. Bur., 1939). 6, no. 4, 31 pp., 1938. HUBER, G., Les brumes de printemps et d'ete FINDEISEN, W., von, Der Aufbau der Regen- sur les eaux froides des parages de Terre- wolken, Zeit. fiir angw. Met., Jg. 55, pp. Neuve, La Meteorologie, 202-213, Avril 208-225, 1938. [Valuable paper]. pp. a Juin, 1929. Die FINDEISEN, W., Kondensationskerne HURD, W. E.. Fog at sea, U. S. Hydrographie Entstehung, chemische Natur, Grosse und office. Pilot Chart of the No. Atlantic Ocean, Anzahl. Beitr., z. Phys. d. fr. Atm., Bd. 25, on backs of issues from Nov. 1927 and later. pp. 220-232, 1939. HUTCHINSON, H. B., A fog situation in the FINDEISEN, W., iJber Wasserdampfiibersdt- United States during the winter of 1928-29, tigung in Wolken, Beitr. z. Phys. d. fr. Atm., Mass. Inst. Tech. Met. Course, Prof. Notes. Bd. 20, pp. 157-173, 1933. No. 3, 1930, out of print. )

BIBLIOGRAPHY 225

HUTCHISON, H. E., and K. C. Kink. On MAL, S., Forms of stratified elouds, Beitr. z. the structure of marine air over the San Phys. d. fr. Atm., Bd. 17, pp. 40-88, 1931. Fernando Valley, Calif., in relation to fore- Abstr. QJRMS, 1931, p. 413-22) casting summertime stratus, M. W. R., v. MUGGE, R., Wolken in Bewegung, M. Z., v. 68, p. 16, 1940. 54, pp. 81-90, 1937. INT. MET. COMMISSION, COMMITTEE FOR MiJLLER, H., Beschleunigungsniessungen im THE STUDY OF CLOUDS, International Fluge zur Erforschung der atmosphdrischen atlas of clouds and of states of the sky, Pt. Luftunruhe, Beitr. Phys. fr. At., Bd. 21, pp. 1, General Atlas, Paris, 1932, 113 p ; Pt. 2, 283-308, 1934. Tropicaux, Paris, 1932, 26 Nuages p. NORMAND, C. W. B., Energy realizable in JACOBS, W. C, Atmos2yheric waves on isen- the atmosphere, QJRMS, v. 64, no. 276, pp. tropic surfaces as evidenced by interfrontal 420-422, 1938. ceiling oscillations, M. R., v. W. 65, pp. NORMAND, C. W. B., Kinetic energy liber- 9-11, 1937. ated in an unstable layer, QJRMS, v. 64, KOCHANSKI, A., Sur les courants thermiques no. 273, pp. 71-74, 1938. Also id., v. 63, p. . . lors dee Cumulus, Lwow, Geophys. Inst. 321-2. (See comments and improvement by Univ., Komunikaty, Tom. 8, nr. 109, pp. Arakawa, MZ, v. 55, 1938, p. 262-4.) 811-427, 1936. PEPPLER, W., Beitrage zur Kenntnis des KOCHANSKI, A., Le regions de la thermique Cirrusniveaus. Gerl. Beitr. Geophys., v. 50, atmospherique en Silesie, Lwow, Geophys. pp. 156-170, 1937. Inst. Univ., Komunikaty, tom 9, nr. 115, pp. PEPPLER, W., Studie Uber die Aerologie des 138-184, 1937. Nebels und Hochnebels, Ann. d. Hydr., 1934, KOPP, W., Aerologie einiger Wolkenformen H. 2, pp. 49-58. und W ellensysteme in der Atmosphare, PEPPLER, W., Der tdgliche Gang der Tempe- Beitr. z. Phys. fr. At., v. 13, pp. '198-217, ratur und Feuchtigkeit an Wolkenoberfld- 1927. - chen, Lindenberg Obs., Arbeit., Bd. 15, pp. KOPP, W., Auslosung von Fallstreifen in 185-193, 1926. ACu-Niveau durch einfallende Ci-Fallstrei- PEPPLER, W., iJber die Dunstsehichten in fen. Mitt. d. preuss Aeron. Obs. Lindenberg, der freien Atmosphare nach Beobachtungen pp. 148-153, 1928. der Wetterflugstellen, Beitr, z. Phys. d. fr. KOPP, W., ijber Angaben von Wolkenschich- Atm., Bd. 24, pp. 260-269, 1938. ten und Schichtdicken durch Aerologische PEPPLER, W., iJber die Temperaturabnahme Stationen fiir die Zwecke des Luftverkehrs, in Nimbuswolken, MZ, 1928, h. 5, pp. 161- Lindenberg, Mitt. Aeron. Obs., pp. 135-139, 166. plates. PEPPLER, "W., Zur Aerologie der Wolken, KOPP, W., Merkwiirdige dynamische Vor- besonders des Nimbus, Beitr. Phys. fr. At., gdnge bei benachbarten stationciren Cumuli, Bd. 23, h. 4, pp. 275-288, 1936, (Crit. by Beitr. z. Phys. d. fr. Atm., Bd. 20, pp. 281- Brooks, BAMS, Jan. 1937, p. 24). 288, 1933. PETTERSSEN, S., Contribution to the theory KOPP, W., Studien Uber den Einfluss von of convection, (Jeofys. Pub., v. 12, no. 9, Dunst und Wolkenschichten auf die ther- 23 pp., 1939. Tnische Struktur der Atmosphare, Beitr. z. PETTERSSEN, S., On the causes and the Phys. d. fr. Atm., Bd. 15, pp. 264-270, 1929. forecasting of the California foa, J. Aeron- KOPP, W., iJber Wolkenmessungen im Zusam- aut. Sci., Vok 3, No. 9, pp. 305-309, 1936. menhang mit der Wetterlage, Lindenberg Reprinted, BAMS, v. 19, pp. 49 55, 1938. Obs., Arbeit, Bd. 15, pp. 271-291, 1926. POULTER, R. M., Cloud forecasting: the KOSCHMEIDER, H., Aufwind und Segelflug, daily use of the tephigram, QJRMS, v. 64, Die Naturwiss., v. 27, 1939. 645-54 (bib- pp. pp. 277-292, 1938. (Comment, p. 541.) ; v. liog. 66, p. 153, 1940 ; reply, v. 66, p. 84. KRICK, I. P., Forecasting the dissipation of RAMDAS, L. A., and S. Atmanathan, A note fog and stratus clouds, J. of the Aeronaut. on fog and haze at Poona during the cold Sei., N. Y.. July, 1937, pp. 366-71. season, India Met. Dept., Sei. Notes, v. 5, LANGE, K. O., Die aerologischen Verhdltnisse no. 54, pp. 89-96, 1932. in Cumulus-und Cumulo-Nimbus Wolken, REFSDAL, A., Der feuchtlabile Niederschlag,, Beitr. z. fr. 131- Phys. d. Atm., Bd. 16, pp. Geofys. Publ., v. 5, No. 12, 1928. (See crit. 137, 1930. by J. Bjerknes, Geofys. Publ., v. 12, no. 2,

LAY, R. B., Berechenbarkeit von Wolkenhohen, p. 14) ; rev., MWR, v. 58, p. 467. Deutsch. Flugwetterdienst, Erfahrungsbe- richte, Sonderband 1, pp. 81-84, 1930. [Nom- REFSDAL, A., Precipitation from air in ogram for de'w-point formula for cloud moist-labile equilibrium, M. W. R., v. 58, p. heights.] 467, 1930. LITTWIN, W., Die Energie trocken- und RENNER, R., Zur Frage der Temperatur in feuchtlabiler Schichtunqen, Forschungsar- entwicklungsfahiaen Quellwolken, Ann. der beiten des stattl. Obs., Danzig, Heft 4, 1935. Hydr., Jan. 1939, pp. 38-42. LITTWIN, W.. Energy of conditional instab- RICHTER, J., Was sagt die Wolkenformen ility. M. W. R., V. 64, pp. 397-400, 1936. dem Seeman Uber Zustande und Vorgange LOCKHART. W. M., A winter fog of the in- der Atmosphare, Der Seewart, v. 8, 1939, p. terior (of Calif.), in: Mass. Inst. Tech. Met. 97-112, 145-50. Papers, v. 1, no. 2, pp. 11-20., 1931. RODEWALD, M., Arktischer Seerauch in sub- LOHR. A., Cloud flights, M. W. R., v. 59, pp. tropischen Breiten, Der Seewart, 1937, pp. 430-431, 1931. 86 ff. LOTHMAN, A. A., Fog forecasting for fire ROSSBY, C. G., On the effect of vertical con- control in southern California, M. W. R., v. vection on lapse rates, Jn. Wash. Acad. Sci., 66, pp. 134-135, 1938. v. 20, no. 3, 1930. LU, A., A preliminary study on the fogs of the China coast, (Abstract in Eng.), Met. ROSSMAN, F., Beobachtungen Uber Schnee- Wetter, Bd. Mag. (China), v. 13, No. 9, pp. 581-585, rauchen und Seerauchen, Das Sept., 1937. 51, pp. 309 ff., 1934. 226 AIR MASS ANALYSIS

SAITO, H., On the theory of cloud formation U. S. WEATHER BUREAU, Definitions of in the winter monsoon field, Jn. Met. Soc. hydrometeors and other atmospheric phe- Jap., V. 16, no. 1, p. (2). nomena, 34 pp., 1938, Mimeo. SCHERESCHEWSKY, Ph.. et Ph. Wehrle, La VERNON, E. M., The diurnal variation in semaine Internationale des nuages: A. Etude ceiling height beneath stratus clouds, M. W. de la journee du 25 septembre 1923 sur R., V. 64, pp. 14-16, 1936. I'Europe occidentale, France, Office Nat. Met., Memorial no. 16, 37 plates [cloud pic- VERYARD, R. G., Some observations on the tures], 1926. therynal structure of cum,uliform cloud, In- SCHERESCHEWSKY. Ph., et Ph. Wehrle, dia Met. Dept., Sci. Notes, v. 6. no. 64. pp. Les systemes nuageux, France, Office Nat. 87-112. 1935. Met., Memorial no. 1, 77 pp., 1923. WADSWORTH. J., A study of visibility and SCHMIDT, W., Wird die Atmosphare durch fog at Malta, London. Met. Office, Geophys. Konvektion von Erdoherfiache her erwarmt, Memoirs, no. 51 (v. 6), pp. 3-23. 1930. MZ, V. 38, 1921, pp. 262-8. WALKER, G. T.. Clouds and cells, QJRMS. K., SCHNEIDER, Wolkenbeobachtungen bei V. 59, no. 252, pp. 389-396. 1933. Flugzeugaufstiegen, Lindenberg Obs.. Ar- beit., bd. 15, pp. 261-270, 1926. WALKER. G. T., Some recent work on cloud SCHWERDTFEGER. W., ijber die hohen forms, QJRMS, v. 65, no. 278. pp. 28-30. 1939. Wolken, Berlin, Reichsamt fiir Wetterdienst, Wissenschaftliche Abhandlungen, Bd., V, WEGENER, K., und K. Schneider. Ergebnisse Nr. 1, pp. 1-33, 1938. 1922-1923 an der Flugstelle des Observato- SOARING Society of America, Gliding and riums Lindenberg : part 3. sect. 13-18. Lin- Soaring manual, 69 pp.. 1938. denberg Obs.. Arbeit, Bd. 15, pp. 244-250. 1926. STONE, R. G., Fog in the United States and adjacent regions, Geograph. Rev., N. Y., WEGENER, K., und K. Schneider, Flug und Jan. 1936, pp. 110-136. Wind, Lindenlserg Obs.. Arbeit., Bd. 15, pp. 251-260, 1926. STuVE, G., Wolken und Gleitfldchen, Arbeiten der Preuss. Aeronaut. Obs., Lindenberg, Bd. WILLETT, H. C, Fog and haze, M. W. R., v. 435-468, valuable 15, pp. 214-224, 1926. 56, pp. 1928. [The most treatise; bibliog.] SUCKSDORFF, G. A., Die Stromungsvorgdnge in Instabilitcitsschauern, M. Z.. Bd. 52, pp. WILLETT, H. C, Synoptic studies in fog, 449-452, 1935. Mass. Inst. Tech. Met. Papers, v. 1, No. 1. 1932. SUCKSDORFF, G. A.. Kaltlufterzeugung durch Niederschlag, M. Z., v. 55. pp. 287-292, 1938. WOOD, F. B., The formation and dissipation SORING, R., Die Wolken, Leipzig, 1936, 122 of stratus clouds beneath turbulence inver- pp. [Best and only modern treatise, bibliog. sions, Mass. Inst. Tech. Met. course. Prof. Rev. in BAMS, v. 20, p. 63-6, 1939.] Notes, no. 10. Dec. 1937. 27 pp. BAMS. v. 97-103, 1938. THRAN, Peter, Untersuchungen uber das 19, pp. Wesen statisch steigender, trockener Luft- ZACK, E. G., Characteristic of frontal cloudi- massen in der Atmosphare und Uber die ness by the aeroplane ascent records, Mos- Grosse und Wirkungsweise der dabei auftre- cow Met. and HydroL, no. 8, 1937. pp. 15- tenden Scheinreibung, Dissertation, Albertus- 29. Univ., Konigsberg. 1937. 46 pp. ZACK, E. G., Characteristic of intramassive TSUKUDA, K., On the sea fog in the No. inverse cloudiness by the data of airplanes Pacific Ocean, Geophys. Mag., Tokyo, v. 6, ascents, Moscow, Met. and Hydrol.. 1938. no. p. 147 S, 1932. 5. pp. 33-50. INSTRUMENTAL PROBLEMS AND DEVICES

DIAMOND, H.. and others ; An Improved LANGE, K. O., On the technique of mete- radiosonde and its performance, Jn. Res. orological airplane ascents, Mass. Inst, of Nat. Bur. Standards, v. 25. no. 3, 1940. Tech., and Woods Hole Oceanographic Inst., pp. 327-369 (see also no. 2, for Automatic Papers in Met. and Phys. Oceanogr., v. 3, weather station), bibliog. no. 2, 52 pp., 1934. MARKS, A. M., Jr., Reminiscences on A P DINKELACKER, Otto, Darstellung einer In- O B flights and fliers, BAMS. v. 21, pp. 18- version und eines Kaltlufteinbruchs in der 22, 1940. Hohe, MZ, Bd. 54, pp. 477-479, 1937. [Dens- SPILHAUS, A. P., An air mass indicator, ity channel exper.] BAMS, V. 16, pp. 31-33, 1935. DRAPER, C. S., Aircraft instruments in me- SPILHAUS. A. F., A new design of a dew- teorological flying. Mass Inst. Tech., and point and temperature recorder, BAMS, v. Woods Hole Oceanographic Inst., Papers in 16, pp. 119-122, 1935. Met. and Phys. Oceanogr., v. 3. no. 2, pp. SPILHAUS, A. F.. The transient condition of 53-60. 1934. the human hair hygrometric element, Mass. Inst, of Tech., Met. Course Prof. Notes, no. DUNMORE. F. W.. An improved electrical 8, 1935, 18 pp. hygrometer and its applications, BAMS, v. 21. pp. 249-256, 1940. WEICKMANN, L., iJber Radiosonde-Kon- strucktionen, Denkschrift, Int. Met. Org.,

HAYNES, B. C, A density channel for illus- Int. Aero. Kom., Berlin, 1937. 85 pp. : Nach- trating fronts and occlusions, BAMS, v. 20, trag, 1939. (Bibliog.) [Review of all work pp. 37-38, 1939. done on radiosondes] KLEINSCHMIDT, E., et al, Handbuch der ZISTLER, Peregrin, Hohe Registrierballon- meteorologischen Instrumente und ihrer aufstiege in Milnchen und der Einfluss der Auswertung, Berlin, 1935, [Standard work, Sonnenstrahlung, Deutsches Met. Jrb. Bay- but emphasizes European practice], 733 pp. ern, 1934, Anhang C, 14 pp. BIBLIOGRAPHY 227

BIBLIOGRAPHY ADDENDA

These additions should read alphabetically in Sections with corresponding headings

Section B Section H4

WEXLER, H., CoTnparison of observed and PFEIFFER, C. A., Uber Feinregistrierung computed outgoing radiation intensities. des Luftdruckes, MZ, v. 57, H. 5, 1940, pp. 177-84. Trans Amer. Geophys. Un., 1940, pt. 2, p. 264-5.

Section I Section C EXTERNBRINK, H., Lenticularis Wolken und lokale Diskontinuitatsfl-achen, MZ, v. 57, H. M., EADAKOVIC, Zum Einfluss der Erdrota- 2, 1940, p. 55-61. tion auf die Bewegung auf der Erdober- flache, MZ, 1914, p. 384-392 ; also Schubert, FINDEISEN, W., Die Entstehung der 0° - id., 1919, p. 8; 1920, p. 259; Schmidt, id., Isothermie und die Fraciicumulus-Bildung

p. 100 ; p. ; Thorkelsson, id., 1920, 1921, 212 unter Nimbostratus, MZ, v. 57, 1940, H. 2, 1925, p. 407. p. 49-54.

LOHLE, F., Uber die prognostische Bedeutung Section Dl der Schichtung des Dunstes, MZ, v. 57, H. 2, 1940, p. 73-9. MEINARDUS, W., Die interdiurne Verander- lichkeit der Temperatur auf der sudliche Section D3 Halbkugel, MZ, v. 57, H. 5, 1940, p. 165-76. SCHAMP, H., Luftkorperklimatologie des grie- chischen Mittelmeergebietes, Frankfurter Section El Geogr. Hefte. 13, 1939, 75 pp.

ALLEN, R. A., et al. Report on investigations into forecasting for five-day periods. Papers Section G5, 1935 to date in Phys. Ocean, and Met., MIT and WHOI, vol. 7. no. 3, 1940. (abstr. of part, by SCHNEBEL, L., Beitrag zur Zyklogenese. Willett, Trans. Am. Geophys. Un., 1940, pt. Archiv d. deutsch. Seewarte, v. 59, no. 6, 2, p. 258-61.) 1939, 28 pp. .

228 AIR MASS ANALYSIS

Glossary of Elementary Terms Used in Articles I to IX absolute humidity (11)^—the mass of adiabatic rate of cooling with ascent water vapor present in a unit vol- for saturated air (I) —a rate which, ume of air, or the density of the varies chiefly with the temperature water vapor. and hence has no fixed value, absohitely stable (I) —a vertical dis- air mass (II) —an extensive body of tribution of temperature such that, air which approximates horizontal whether the air be dry or saturated, homogeneity. particles will tend to remain at characteristic curve (IV) —the curve their original level. In this case the joining the significant points of an lapse rate must be less than the aerological sounding when plotted saturation adiabat at the prevailing on the Rossby diagram. temperatures. cold front (V and VII) —the discon- absolutely unstable (I) —a lapse rate tinuity in front of a wedge of cold greater than the dry adiabatic; air which is displacing warmer air both dry and saturated air are un- in its path. stable. Also called a super-adiabatic lapse rate. conditional equilibriwn (I)-—a vertical distribution of temperature adiabat (I) —a curve along which a thermodynamic change takes place such that the layer is stable for dry air but unstable for saturated air. without the addition or subtraction In this case the lapse rate lies of heat. In the case of the atmos- between the dry and the saturated phere a dry adiabat is generally adiabat. Also called conditional in- considered a temperature-height or stability, or conditional stability, temperature-pressure curve along and moist labile equilibrium. (See which a rising or sinking air par- latent instability.) ticle will fall providing no saturation occurs and providing, of course, conservatism (II) —the degree of con- that no heat is given to or taken stancy of a meteorological element Simi- from the particle in its path. when the given air mass is subject {saturation larly a ivet adiabat to modifying factors. adiabat, condensation adiabat, or pseudo-adiabat) is a temperature- convective instability (IV) —a verti- height or temperature-pressure cal distribution of temperature and curve along which the saturated ris- moisture such that lifting of the ing particle will fall. entire layer will eventually lead to instability with respect to dry air. adiabatic chart (III) —a thermo- In convective instability the equiva- dynamic diagram in which tempera- lent-potential temperature decreases ture is plotted against pressure with elevation. Also called "poten- scale, (either on a logarithmic tial instability". "Convective equi- or pressure to the 0.288 power) and librium," however, merely means an in which dry adiabats are con- unstable (adiabatic) lapse rate. structed. The chief use of this repre- chart is for evaltiation of aero- depegrain (VIII) —a curve logical soundings. senting the behavior of the dew- point with pressure changes for a adiabatic process (I) —a thermo- given sounding, drawn on the tephi- dynamic process in which no heat gram. is transferred from the working substance to the exterior or vice discontinuity (I) —a zone of compar- versa; a thermally insulated pro- atively rapid transition of the me- elements. These dis- cess. . teorological continuities are not mathematically adiabatic rate of cooling with ascent abrupt, but are rapid transitions for dry air (I) —very nearly con- troposphere at 1 de- stant in the ^Roman numerals following each term refer gree Centigrade per 100 meters (see to the article in which the topic is discussed adiabat) in some detail. . —

GLOSSARY 229

compared with the ordinary tran- through the horizontal convergence sitions in one and the same air of air currents possessing widely mass. (Practically synonymous different properties. with front.) frontolysis (VII) —the destruction of dry air (I)- -air which is not satu- fronts generally brought about by rated. horizontal divergence at the discontinuity zone. emagram (VIII, IX) —any adiabatic diagram with coordinates T, log p. instability (I) —the opposite of stabil- Areas are proportional to energy as ity; a lapse rate in which particles on the tephigram. will be readily displaced vertically upon small impulse. (Also called energy diagram (III, VIII, IX) any — lability.) See: conditional, latent, thermodynamic diagram on which pseudo-, mechanical and absolute in- area is proportional to energy; such stability. as the tephigram or emagram (which see) instability showers (V) —s h o w e r s equivalent-potential temperature (II) caused by steepening of the lapse- —the temperature a given air par- rate in any way, such as the rapid warming of the lower layers of ticle would have if it were brought adiabatically to the top of the at- a cold current as it moves over a relatively warm surface. In most mosphere (i.e., to zero pressure) so cases there is an appreciable ad- that along its route all the moisture were condensed (and pre- dition of moisture to the lower polar cipitated), the latent heat of con- layers, as for example, when a continental current over a densation being given to the air, moves and then the remaining dry sample body of warm water. of air compressed adiabatically lapse rate (I) the existing rate of to a pressure of 1000 millibars. — change of an element, commonly equivalent-potential temverature dia- temperature, with height in a given gram—see Rossby diagram. layer of the atmosphere. equivalent temperature (II) —the tem- latent instability (VIII) on the perature a particle of air would tephigram, when the area of posi- have if it were made to rise adia- tive energy is greater than the batically to the top of the atmos- negative energy area (this is more phere (i. e., to zero pressure) in properly called real latent instabil-

such a manner that all the heat ity) . In general latent instability of condensation of the water va- refers to the energy that can be re- por were added to the air and leased after the convection reaches the sample of dry air were then the condensation level. It is the brought back adiabatically to its case of conditional instability where original pressure. the air is moist enough for convection to form clouds. (See also pseu- estegram (VIII) —the characteristic do-instability. ) curve of wet bulb temperatures of a sounding plotted on a tephigram loop (or bent) back occlusion (VII) — or pseudo-adiabatic chart. an occluded front which has bent back in the rear of the cyclone so front (V, VI and VII) —the discon- that it appears in the meteorologi- tinuity between two juxtaposed cur- cal field as another front behind the rents of air possessing different cold front. In most cases these oc- densities. Most frequently fronts clusions are of the cold front type. represent the boundary between That is, the air behind is colder different air masses. The so-called than that preceding them. "wind-shift line" is usually a well- instability (I) a lapse marked front. mechanical — rate such that the air density de- fr ontogenesis (VII) —the creation of creases with elevation; for this con- fronts generally brought about dition the lapse rate must be greater — .

230 AIR MASS ANALYSIS

than 3.42 degrees C. per 100 m; also partial potential temperature (III) —

called "auto-convection" , since no the temperature a given air par- initial impulse is needed to set it ticle would have if it were reduced off; "self-starting". adiabatically from the pressure exerted solely by the dry air to a mixing ratio (III) —the mass of water pressure of 1000 mb. vapor per unit mass of perfectly e = r [i000/(p—e)]0-288 dry (absence of water vapor) air. d w = 622 e/(p e) grams per (see symbols) kilogram (see symbols) penetrative convection (IV) —^^small convective up-currents locally pen- modification of air mass properties etrating an overlying more stable (II) the change in the values of — layer without generally or greatly meteorological elements within the altering the existing atmospheric an air mass due to such influences stratification. as radiation, turbulence, subsidence, convergence, and so on. These modi- Poisson's equation (I) —the relation fying influences tend to destroy the between temperature and pressure original horizontal homogeneity of in dry air which is undergoing the air mass. adiabatic transformation. T,/T. = ipjp^)'^'' area (VIII) the area on a negative — polar front (VII) —the frontal zone enclosed between the tephigram between air masses of polar and path of the rising particle and the those of tropical origin. surrounding air when the rising positive area (VIII) the area on a particle is at every stage in its — tephigram enclosed between the ascent colder than the environment. path of the rising particle and the surrounding air when the rising neutral equilibrium (I) —a vertical particle is at every stage in distribution of temperature such its ascent warmer than the environ- that a particle of air displaced ment. from its level neither assists nor resists the displacement; that is, at potential temperature (II) —the tem- every level the density of the dis- perature a given particle of air placed particle is equal to that of would have if it were reduced adia- the surrounding air. In the case batically to a pressure of 1000 mb. of dry air the corresponding lapse e = T (lOOO/p)'"'' rate is that of the dry adiabat; in pseudo-adiabatic (IV) the process the case of saturated air, the satu- — wherein a saturated air particle ration adiabat. undergoes adiabatic transforma- occluded front (VII) or occlusion— tions, the liquid water being as- the front formed when and where sumed to fall out as it is con- the cold front overtakes the warm densed. front of a cyclone. This front pseudo-adiabatic chart (III, VIII) — marks the position of an upper an adiabatic chart on which wet trough of warm air, originally adiabats are also drawn; lines of from the warm sector, which has saturation specific humidity are been forced aloft by the action usually added too. Used for analyz- of the converging cold and warm ing stability conditions in a sound- fronts. Occlusions may be of the ing (see emagram) warm front type in which the air pseudo-(latent) instability (VIII) —on in advance of the front is colder the tephigram, when the area of than that behind, or of the cold positive energy is less than the area front type, in which the air in ad- of negative energy. vance is the warmer. relative humidity (II) —the ratio of Occlusion is also the term used to the actual vapor pressure and the denote the process whereby the maximum vapor pressure possible warm air of the cyclone is forced at the same temperature. from the surface to higher levels. / = e/e (see symbols) . : ;

BIBLIOGRAPHY 231 representative observations (II) — subsidence (IV)-—an extensive sink- those which give the true or typi- ing process most frequently ob-

cal conditions of the air mass ; hence served in polar anticyclones. The they must be relatively uninfluenced subsiding air is dynamically by local conditions and taken from warmed and made more stable. outside the transition zones and fronts. superadiabatic (I, VIII, IX) —a lapse- greater than the dry adiabatic Rossby diagram (III) —a thermo- rate dynamic diagram making use of absolute instability. Mechanical in- implied also. the highly conservative air mass stability may be properties: partial potential temperature, equivalent-potential tem- surface of discontinuity (V) —the perature and mixing ratio. sloping boundary zone between air masses of different properties (see secondary fronts (VI) —fronts which discontinuity) develop at some distance from the principal fronts of the cyclone. symbols—used throughout the series fronts often the result These are and in the formulas given herein of dynamic effects behind the cold front, are loop oc- or merely back e =vapor pressure clusions. e = saturation vapor pressure ?n slope of a front (V) —the tangent of / = relative humidity the angle formed by the discon- p =total pressure tinuity surface and a horizontal q = specific humidity plane. t, i' = dry, and wet, bulb temperature, resp., in °F or in °C source region (II) an extensive area — r= absolute temperature of the earth's surface character- T"= wet-bulb temperature (°A) ized by sufficiently uniform surface w ==mixing ratio conditions and which is so placed in 9 = potential temperature general circulation that respect to T = equivalent temperature masses of air may remain over them -E sufficiently long to take on fairly =equivalent-potential tem- definite properties. S perature e = partial potential temperature specific humidity (II) —the mass of ii water vapor in a unit mass of moist e'=wet-bulb potential tempera- air. g=622 e/p grams per kilogram. ture. = entropy squall head (VI) —the piled up cold (f) air at the cold front, sometimes taking the form of an overhanging tephigram (VIII) —a thermod^mamic tongue. Also "line squall", diagram for estimating the quantity of available convective energy stability (I) —a vertical distribution in the overlying air column; also of temperature such that particles applied to the graph of an in- will resist displacement from their dividual sounding plotted with co- level. In the case of dry air the ordinates temperature and entropy. lapse rate for stability will be less than the dry adiabat; in that of zone at a saturated air, less than the satura- transition zone (V) —the tion adiabat. discontinuity wherein the properties are characteristic neither of one stratification (V) —a layering of the air mass nor the other, but lie some- atmosphere, so that each layer is where between the two. It is now characterized by a particular tem- customary to assume that all the perature distribution and moisture air in the transition zone belongs content. Instability tends to wipe to the colder air mass, the air in out stratification as it brings about warm sectors being considered more mixing. nearly homogeneous. .

232 AIR MASS ANALYSIS unstable (I) —a vertical distribution warm sector (VII) —the air enclosed of temperatvire such that particles between the cold and warm fronts of air,, because of their lesser or of a cyclone. than the surround- greater density wave disturbance (VII) —a deforma- sink of their ing air, will rise or tion produced along a front. These own accord once given an initial waves travel along the discontinuity impetus up or down. For dry air surface often producing new cy- the unstable lapse rate is greater clones. than the dry adiabat; in the case of saturated air, greater than the wet-bulb temperature (III, VIII) —the to which a saturation adiabat. lowest temperature wetted ventilated thermometer (as of a psychrometer, e.g.) can be (VII) a front whose up23er front — cooled, i.e., by evaporation, while principal development and evidence not strictly a temperature of the is in the upper air, usually the air, it is a function of dry bulb, active upper cold front of a warm relative humidity and barometric front type occlusion. pressure. On the adiabatic chart or tephigram: find the intersection vajjor pressure (II) —^the partial pres- of the dry adiabat and specific hu- sure of the air exerted solely by midity line and then follow down the water vapor molecules. the wet adiabat to the original pressure level of the point in question. (See: estegrain; latent instability; ivarm front (V) —the discontinuity at 2')seudo-instability .) The wet adiab- the front of a warmer air mass ats are isotherms of equal wet-bulb which is displacing a retreating potential temperature (also equiva- colder air mass. lent-potential temperature)

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