A I^AfiTuivw.*^ An Introduction to the Study of Air Mass and Isentropic Analysis 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 — IV 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 equi- librium", 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) y3<a<y (Conditional:) stable for dry air, unstable for saturated air. a = y Neutral for dry air (equal to dry-adiabatic lapse rate) y <a < 3.42 C° per 100 m (Absolutely) unstable (but not self-starting) 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 topogra- phy 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.