62 MONTHLY WEATHER REVIEW. FEBRUARY,1921 The humidity at 8 a. m., figures 5 and 6, presents winter and vice versa. When monthly means are used, curious variations. Although 60 per cent of instead of daily, a third mode due to spring and fall days, the highest number of an month, are without rain, appears, but this is only a feature of the method of corn- yet 15 er cent of the days, tI e highest number of any putatioii and daily data should be used in place of monthly month, %ave a humidity at 8 a. m., two hows a&r sun- when practicable. The dual mode in the range of rise, of 98 to 100 per cent. This is due to the prevalence monthly maximum tem erature is probabl a snow cover of fogs in that month, the fogs, in turn, being caused by and humidity effect. #he dominant mo&, 32') corres- the prevalence of clear nights with diminished tempera- ponds to the mode for monthly range of minimum ture. (Fig. 7.) The modal period for dense fog is temperature, 31'. to 17. The humidity then diminishes to Figure S shows how histowanis of monthly tempera- November, the '' Indian summer " month, and increases ture and precipitation, whicx are veri easily pre ared. again with the formation of snow cover in . It from the station annual summaries, alt ough of diP erent is rather surprising to find the mode for 8 a. m. humidity nat.ure from histograms inade with the daily data, are in January and February to be 98 to 100 per cent. The useful in comparing climates with respect to the general high hum'idity occurs on mornings of "radiation" cold features of rainfall and temperature. and is often accompanied by rime and fog. It is unfor- tunate that data of daily masimum and minimum humidity are not available. The smooth curve marked by the tops of the columns REFERENCES. of no precipitation, figures 5 and 6, is interesting, as is Hann, Julius von. also the variation in the number of days with a trace. In Hawdbiich der h'liniatologie, vol. 1, lWS, p. 31. summer traces of precipit-ation tend to evaporate before Hann, Julius von. the reach the ground. In winter traces are prominent Lehrbiwh der Meteoroloyie, 3d od., 1915, pp. 19-20. in t.Tl e form of snow flurries. The curve of days with no precipitation shows inverse relation to that of days with Marvin, Charles Frederick. Elementary Notes on Least Squares, the Theory of Statistics 10 tenths clouds, or sky entirely overcast, figures 3 and and (.'orrelation for Meteorology and Agriculture, MONTHLY 4. A peculiar feature of the latter is that an decrease WEATHERREVIEW, October, 1916, 44: 551-569. in the number of overcast days is divided rat1 er evenly among the days with lesser amounts of cloudiness, the Tolley. Howard Ross. number of entirely clear days remaining fairly constant I+eguruicy (lurves of Vliniatic Data; MONTHLYWEATHER throughout the year, thou h greatest in September. REVIEW,November, 1916; 44: 6346.13. Since 1905, or for 15 years oB the 89, the daily amount of hfONTHLY WEATHERREVIEW, Octobcr. 1916; 44: p. 566. cloudiness has been determined by observations every Hallenbeck, Cleve. two hours of the amount, kind. and direction of movenient Forecasting Precipitation in Percentages of Probability; of the clouds. MONTHLYWEATHER REVIEW, November, 19%; 48: p. 645. Fkure 7 shows the annual distribution of the different Trotter, Spencer Lee. daily weather elements. The two modes of maximum, Local Peculiarities of Wind Velocit and Movement Atlantic minimum, and mean tem erature are due to the fact- Seaboard, Eastport, Me., to Jacisonville, Fla.; MONTHLY that there is rather rapidp transition from summer to WEATHERREVIEW, November, 1920; 48: p. 634.

TEMPERATURE VARIATIONS IN THE AND ELSEWHERE. 5s/.sa4 ; so/ By ALFREDJ. HENRY,Meteorologist. [Weather Bureau, Washington, D. C., February, 1921.1

SYNOPSIS. circulation of the atmosphere, aa modified, of course, by the secondary circulation due to the movement of cyclones and anticyclones. In the first part of the er effort is made to discover to what extent In order to get beyond the influence of the latter the study waa eriods of abnormally K",K or abnormally low temperature in the extended to imlude certain tropical stations, viz, Batavia, Habana, Enited States synchronize and also as to whether or not there is evi- , and Arequipa. Consecutive means were also computed dence of a periodicitv in the occurrence and recurrence of these for these stations. phenomena. The bash material for the study was 12-month consecu- Both tropical and teniperatc zone stations show very clearly the

i i i

F " I

Y

FIO. l.-Smoothed temperature means, each tive or overlapping monthly means of the temperature for fairly large ptwixteiire of short-period variations of about 40 months in length; rgraphic districts. The districts used are (1) the New oc*casionally. for rcasons not undcmtoorl. some of these ahorbperiod tates, (,2)Minnesota, (31Colorado, (4')Washington, and (5) Louisiana. niasima ani1 niininia are greatly intensified and consequently appear The monthly mean t,emperature for each of these diatricta was originally as primary maxima or minima in the series. The length of the interval computed from the means of all of the individual stat,ions therein. bet ween these so-called primary maxima and minima ia greater than The period 1858-1919 furnished the data for the study. and probably some multiple of the 40-month period. As WBB to have been ex ected, the control of the changes in tempera- One of the chief characteristics of the data is the tendency of any ture of the various parta ofthe United States is clearly that of the general marked variation in the temperature to be followed by another one of Unauthenticated | Downloaded 10/01/21 06:18 PM UTC hwmy,1921. MONTHLY WEATHER REVIEW. 63

opwta phaee Slmost immediately. While this tendency amounta THE MATERIAL USED. to almost certainty it is useless for forecast purposes because there is no means of discovering the precise diiration of any existing phase. It is pro osed in what follows to determine the varia- A comparison of the temperature variations in the border region tions in t e annual mean temperature not from the between tropics and subtropics led to the conclusion that the influ- E ence of the general circulation at times extends to the northern portion annual means for individual stations, but by the use of of tropical areas. There also seems to be in o eration at tinies a com- 12-month consecutive means for a few geographic dis- mon temperature control for both Tropics anftemperate 7nnes. Ex- trict.s in the United States. The districts selected are: tracts from the Rmau Mondial for 1910, 1911. and 1912 are quot,ed in (1) The States, (2) Minnesota, (3) , su rtof this view. literature of the sun s t terrestrial temperature relation is very (4) Washington, and (5) Louisiana. The fmt of these is briefly touched upon and tE difficulty of separating the terrestrial representative of the Atlantic Coast States above 40' N. from the extra-terrestrialinfluences is discussed. The annual tempera- latitude, the second of the continental interior along the -ture variations of the United States as a single geographic unit. is coni- northern border, the third that of the elevated Rocky pared with the sun-spot curve and the resemblances and differences are discuseed. Mountain region, the fourth that of the Pacific Coast Stat.es above 45' N. latitude, and t.he last of the low 1at.itude portion of the United States along the Gulf of . Twelve-montrh consecutive temperature means have been used by Clayton,' and especially by Arctowski,t in his numerous papers upon temperature distribution. The advantage in using t.hese means is in the fact that they enable us to discover the succession of warmer and colder periods that mi ht be wholly eliminated by using t,he mean of the 12 cak endar months. In computin month consecutive means I have called the mean o7 the12- 12 calendar months t,he mean for July, then dropping from t,he sum of the 12 calendar months the mean for the first of the calendar months, January, and adding the mean of the fist calendar month of the immediate1 succeeding year, January, a new sum was obt,ained, whicE divided by 12 gave a mean for August, and so on. While consecutive means for grou s of stations have been computed as above indicated, ?have been obliged, t,o use the means of individual stations for the Tropics. I have comput,ed the consecutive means for four stations, viz, Batavia, Java, for which fortunately there are avail- able monthly means of the maximum tem erature for each month of the period 1S66 to 1914. $he monthly means of temperature published in the Yearbooks of the Belen College Observatory of Habana, , were used for that st.ation. The series of observations maintained at Arequipa, Peru, by Harvard College Astronomical Observatory, although coverin but a short term of ears, tive or negative temperature anomalies, the reason gave satisfactory mean values for that station, and f? nally therefor can enerally be referred back to the secondary the monthly mean temperature as observed by the circulation. %ere are months, however, when the net- Weather Bureau and cooperative observers at Honolulu, work of cyclonic paths is so intricate as to reclude the , formed the last of the series of tropical stations. formation of any logical conclusion as. to .tR e tempera- Obvious1 an attempt to consider the temperature varie ture distribution. In any event a quantitative statement tions of tiT e g obe as a unit, even on a very limited scale, of the influence of the secondary circulation seems to be must take cognizance of the variations in the Tropics. impossible of ascertainment. A common method of I nest plotted the consecutive means for each of the four a proaching the question is to plot on coordinate paper stations named as abscissae against time as ordinates to tfe variations of both the temperature and the suspectcd form the four curves of figure 1.

: I F

I w

Y " m m

1 " w value being the mean of 12 consecutive months. cause thereof and draw freehand curves throu h the REMARKS ON THE CURVES. lotted data inEorder to note the degree of par3 lelism getween the two events. The Tropics-Bafavia.-The curve for t.his station ,me,in general, there is more or less parallelism be- shows very clearly the occurrence Of prOgreSSiVe Warming tween the twoZcurves, yet, on trhe other hand, many , A,e+eor.Jo,,r ",,,. , ,,. 2 Changes in TAmFer&lre .inna~s Sci., contradictions are also present. Iistribution,Unauthenticated N. | Downloaded Y. Acsd. 10/01/21VOI.X~V, 06:18asin. PM UTC 64 MONTHLY WEATHER REVIEW. FEBRU~RY,1921 and cooling throughout the entire term of observations- the epochs of maxima was 49 months; between minima, 48 years. In order to stud these short periodic oscilla- 37 months, counting in each case from maximum to tions, I have formed a tabc giving for each station the maximum and from minimum to minimum. Treating numerical values of the maxima and minima of tern era- the remaining three stations similarly, it is found that ture for the eriods indicated by consecutive num73 ers, the average interval masimum to maximum is as follows: 1, 2, 3, etc. {ee Table 1 for tropical stations and Table Hahana, 45 months; Arequipa, 31 months; Honolulu, 48 la for stations outside the Tropics). This tabulation months. The average int.erval minimum to minimum is shows that at Batavia there were 13 cases of pronounced Batnvin, 37 months; Habana, 31 months; Arequipa, 31 warming in the 48 years. The average interval between months; and Honolulu, -IS months. TABLE1. MASIMUM. -- ...... __ .. Batavia. Java, 1%6-1914. Habana, Cuba, 1888-1918. Arequips, Ycru, 1%~)-1910. Honolulu, Hawaii, 189?-1919. -- - - - Inter- Inter- Iu tcr- Inter- Nal Date. Ha Date. I lo OF. Date. Dah. OF.' val. Val. - .I-_- - --- u. m. JI. 111. y. ni. I 86.2 December, 1W...... -- 1 77.5 1 54.7 July. 1800 ...... -- October, 1592...... a 85.7 November, 1875...... 6 11 2 77.5 August lS!X3 ...... 3 11 2 58.8 C)ctol~er190%...... 2 :1 January, 1897...... 43 3 67.1 March, 1878.. __ ___.___ 24 3 77.5 Ortobe;, lwwi ...... 3 2 3 S.Y. 4 Deeember, Im5 ____ .. 32 May, 1900 ...... 34 4 &KO September lRQ.l-. - -.. 36 4 77.5 May, lsgg ...... 2 7 1 57.8 March, lW9...... 23 May. 1904 ...... 40 5 88.0 December '1585. - -.. -. 43 5 77.7 September, 1902____._ 3 4 October 1906 ...... 25 6 86.8 December: IS..__. __ 30 6 77.5 August. 1905 ...... ? 11 Novemder 1W...... 11 7 86.4 September, 1S91-. .- -. 29 7 78.3 . 7 1 )...... 55 8 67.2 Mwh, 1987...... 56 S 77.5 November,'1915.::::: 3 3 Octohr 1915...... 26 9 88.2 June. 1900...... 69 Januar;, 1919...... 33 10 M.9 October, 1902...... 21 11 sB.9 ...... 33 I 12 86.8 ...... 63 13 87.5 y, 1914 ...... 23 Mean...... IT ...... 17 ...... 27 ...... 133 -__ - - --... I...... MINIMUM. - -- I 1 84.8 %7...... 1 76.6 ...... 1 57.9 October, 1901...... 73. 8 2 M. 4 MaGh lR12 ...... 4 9 2 75.9 2 n2 56.7 February, 19BL...... 74.7 3 84.4 Nare&bcr 1874...... 2 8 3 75.9 November 1891...... 2 33 56. ri Deccmher 1906...... 2 10 3 73.9 August 18618 ...... 2 7 4 85.0 November: 1576...... 2 0 4 76.3 February. '15%...... 1 34 56.3 October, ii...... 2 10 1 73.3 Mareh,im ...... 4 7 5 84.5 August lW...... 3 9 5 76.5 July IS98 ...... 2 5 5 73.3 May 1905 ...... 2 2 6 84.8 &ptember.lss ______2 1 6 7.5.7 SeptLmber. 1901...... 3 ? 6 73.5 7 85.0 % ...... 1 6 October, IWM ____.___.2 7 74.5 ApriiSeptekber, 1908 ...... 1914 ..__.. 35 115 8 85.0 June iS.37 ...... 3 3 July, 1808...... 2 8 74.5 November, 1916 .__.._7 7 9 81.8 Novimber. I890...... 3 5 June. 1910 ...... 3 10 M. 5 Doeember 1893...... 3 1 October, 1913...... 3 11 85.1 -4pri1,rd ...... 5 4 August, 1917...... 3 12 55.5 August.1901 ...... 2 4 13 S5.1 May 1904 ...... 2 9 11 85.4 Jandary,1907 ...... -3 4 I - I ...... -131..._I_...... )...... 2 7 I...... 40 - ...I...... TABLEla. MAXIMUM. Louislanst, lM-1919. I. Colorado, 1.W-1919. I Miiiiiesotn, 18s3-1!119. I New England, lSM-1g1g.

Inter- a F. Dalc. 1 F. Date. - I Y.M. I-. M. 1: M. 1 69.3 June 180...... -- 1 47.5 June, 189p...... 3%4 -- 1 411.4 September, 1858...... - - 2 68.2 I Nodmber. 1893...... 352 40. 2 June, IS94...... 2 43.3 I 412 47.5 January 1892 ...... 2 4 3 68. 4 October, 1896...... 3 11 3 46.5 July. 1896 ...... 3 43.5 383 46. 8 April Ik ...... 2 3 4 69.5 August, 1897...... 0 10 4 47.4 July; 1900 ...... 4 0 4 45.0 ! May, 1!3Ou...... 22 4 47.3 Msy,isgs. _._.___._. . 4 1 5 67.5 August, 1900...... 305 41.6 November.l90l_____.I 1 4 I 5 44. Ij May, 1901 ...... 105 47.1 June. 1901...... 2 1 6 67.7 September, 1902. - -.-. 21 6 46.1 October 1603...... 1 11 I ti 43.2 Scpt.ember, 19U.i...... ti 47.2 November, 1902 .___._2 5 7 69.6 October, 1906...... 41 7 46.4 0ctober:lgM ...... 3 n I 7 41.9 Junc. 19118...... Ki7 46.9 June. 1906...... 4 0 60.7 May, 1911...... 47.2 Se tember,l9lO...... 3 11 S 23 8 47.2 September, 1008. __ __.2 3 6s. 7 ...... 45.3 JuPy,l911 ...... 3 10 I 9 3s. 1 429 47.2 S w.3 August,'l918...... 45.4 March. 1916 ...... 1. 8 I 10 35.7 4 5 10 4s. 0 May,June, 19101913 ...... 31 1 45.8 May, isis...... 11 47.0 July. 1915 ...... 2 1 -_ 12 47.1 February, 1919...... 3 7 82 29

- MINIMUM. 1 65.7 June. 15389...... -- 1 42.9 September. 18ys...... - - 35. 4 July, ls?...... 44.1 - 2 65.6 October 1891...... 24 2 44.0 Aup~~st.lSgl___.__._.2 I1 39.3 Marrh, 1597...... 45. B 4 3 65.3 Decem& lS91--. ___.32 3 41.3 JoIy,1S95 ...... 3 11 39.3 April. IS%...... 43.9 7 4 65.0 October, I'SSS...... 3 10 4 44 5 March 1897 ...... 1 x 3s. 2 Fehruarv. 1904...... 45.5 0 5 05.3 September, 1901...... ? 11 5 4310 Octob&.lSHl.______.1 7 39.1 MBV. ivtii...... I I 45. s 0 6 65.2 March 1904 ...... 26 5 44.2 I Januari. 1903...... I 4 3 39.3 Jul'v. 1W...... __I 45.6 June. lsOl ...... 2 3 7 65.5 Octohb. 1904...... 06 7 44.3 Deeemhr l91i...... 1 11 :i5.5 Feliruary. 1913...... 1 45.5 May. 1902 ...... 0 11 8 68.7 ...... 58 8 45.2 Juue,1906! ...... 1 0 39. 6 Navcmlier, 1015 ...... 43.2 October. 1903 ...... 1 5 9 65.8 July'1912 ...... 21 9 43.4 November,LW)rJ____.. 2 5 .il.9 May, 1917...... I a.1 June. 1907...... 3 8 10 65.B Oetdber, 1914 ...... 2310 41.5 April,l912 ...... 3 5 I 45.0 November, 1910...... 3 5 11 84.0 AugUt, 1917...... 1 3 10 11 42.0 January.1917 ...... 4 9 45. n March, 1912 ...... 1 4 44.8 July, 1914 ...... 2 4 49.5 October, 1917...... 3 3 Marn ...... 3 0 l- - Unauthenticated | Downloaded 10/01/21 06:18 PM UTC Mad- Minima. there are occasions when the Louisiana maximum --- follows that of Habana by a few months and there is Batsvia ...... lS77-78 1Sj7 but a single case, viz, that of 1906, when a maximum in 1w-s 1571-72 one region is not associated with a corresponding maxi- 187 1S74 im iw mum in the other. 1914 18x7 ...... Is90 It is interesting to note that the principal masimum .-.-..--.- of the whole term of pears in Hahana occurred in 1912 :::::::::: :", and in Louisiana in 1911, although the belief is expressed _.__..______..___.___.....___.___.______.._._.__.._l,m 184L that the two niasinia were due to one and the same 1rwm 1~11 cause. The high tem erature at Habana was continued 1Wl 1'JIw-4 ~m IYIO some months longer tP inn in Louisiana, thus indicating 1911-1'2 ...... that t,he cause of the high temperature, whatever it may Arequipa ...... lflo0 1W-4 iw ISOIC~O have been, ceased to function in Louisiana first. The 1WJ ...... Hmnlulu ____.______.___.______.___.____.______..______.____..ISW+W IW temperature in the 1-t named began to fall about nine 19~2-319115 mentalis earlier than in Cuba. The synchronism in the 1~1171913 1915 19ug e ochs of minims is equally good. One would think ~ - tiatf the minimum would occur in Louisia.na a little

Unauthenticated | Downloaded 10/01/21 06:18 PM UTC 66 MON!M-€LY WEATHER REVIEW. FEBRUARY,1921 consecutive means as would be the case if the were used Washington, Colorado, and New England during the in the computation of a mean of the 12 calenB ar months. years 1896-97, and for a few years previous thereto, The response of the temperature in Louisiana to changes show that the march of temperature was characterized brought about by changes in the secondar circulation by alternating periods of high temperature and low is not so great in that State as in the other Btat= consid- temperature occurring without order or system. Fol- ered, although by no means is that influence negligible. the 1896-97 maximum, not only in Louisiana, In the cold season the mean temperature of the State as a 10WiTbut sewhere in the United States, a world-wide depres- whole may be depressed as much as 8' to 10' E". by sion in the temperature set in. It was first manifest in reason of the revalence of cold northerly winds, and, on the United States in the northern and middle Pacific the other han! , when southerly winds are more frequent Coast States, the plateau and Rocky Mountain regions than usual the temperature is elevated by the same in the autumn and early winter of 1898, continuing more amount. It happens, therefore, that the character of the or less intermittently until well into 1899. Louisiana curve is almost entirely that given by the It was also manifest in northern , northwest variations of the winter season. Responding to the sug- . and east Siberia, and in a less degree in the East estion that perhaps a consideration of the variations Indies. While the depression in the northern parts of !uring the summer months might yield important re the Temperate Zone may be referred to the influence of sults, I have computed the anomalies of the months of the secondary circulation, we can not explain the fall in June, July, and August for the term of years available. temperature at Batavia in that manner. The sun-spot As m' ht be expected, thcse anomalies are much smaller curve at that time was descending to the minimum of than l%t ose of the winter, rarely esceeding f3.5' F. The 1901. summers of 1891, 1S92, 1894, 1903, 1908, 1913, and 1917 At this point I wish to introduce some evidence were cool, while those of 1890, 1895, 1896, 1900, 1902, 1906, 1907, 1909, 1910, 1911, 1912, 1915, and 1919 were warm. The tendency, therefore, during the period con- sidered was toward higher temperature, there being a total of 13 warm summers and only 7 cool 01188. In general, the mamma and the minima of the Louisiana curve are not congruent with those of the more northern States, owing doubtless to the fact that the variations in the latter are more directly due to changes in the secondary circulation. The lack of accord in the dates of the maxima and the minima and in the length of the interval between them is clearly shown by the data of phere. This evidence is simply a statement showing Table la. The average interval between the maxima the deviations of the annual mean temperature for that for Louisiana and Minnesota is exactly the same, but ortion of the globe between 20° South latitude and 60' the individual lengths are all different; hence, for the iorth latitude for the years 1910, 1911, and 1912. pur ose of forecasting, the averages are useless. The presentation of these data is possible through the &e extent to whch the temperature oscillations of ublication of the RBseau Mondial by the British Meteoro- the more northern States are damped by changes in an Cgical Office. The data are given in the table next fol- opposite sense due to the influence of the secondary lowing (Table 3). Attention is directed to the columns emulation is easily seen. For example, the curves of headed "Mean Temperature, Departures in OC. "

TABLE3.-Wwkl departurea of temperature and precipitation, 60' North to 20° South latctude, 1910, 1911, and 1912.

1910

Zone No. LatitIldC. ' N?. ot Madeparhue.1911 Meandeparture.1912 stations. departwe. I -_ Temp. I Precip. Temp. I Predp. 1 Temp. I Preclp.

OC. mm. 10 Tropics...... 20' to 100 south ...... 16 -0.10 +256 -0.08 - 18 9 Trmm...... 100 to 00 ...... 11 50.00 - 85 -0.01 -258 8 T&?a...... 0' to 10' North ...... 18 -0.30 - 21 -0.08 -m +o.lo -m 7 Tropics...... 10. to 20' North...... 25 -0.20 +28 -0.04 +128 +o.m -96 6 Extra Trap...... 20' to 30' North. .-..~...... n -0.30 + 51 *am +ee +a10 + 41 5 Extra Trop ...... 300 to i* No%, W.half ...... 19 +0.30 -159 +o.m - 5a -0.30 - 41 5 Extra Tr op...... 30" to 40" North E. ha1f...... 24 -0.30 + 59 -0.10 - 10 4 Extra TrOi,...... 40' to 50' North: W. half ...... 17 +LOO - 67 +o.m+0.10 -+loo 6s -0.m - 10 4 Extra Tr op...... 40' to 50' North, E. half ...... m +0.70 + 66 +&IO + 15 -am +a 8 Extra Trop...... 50" to 60' North W. h?U ...... 11 +o.m -20 -1.10 - 74 -0.m + 8 8 Extra Trop ...... 50" to 60" Nor"m, ' E.- n311...... I 25 +1.10 + 34 +0.90 - 18 -0.60 + 74 The annual deviations of temperature for each of the and of a magnitude that will satisf the requiremente of ears iven are of the same order of magnitude as those the theory of sun-spot control. 5; greater number of geretofore found and assigned to the sun-spot influence, years of observations will of course, afford conclusive thus indicating, it seems to me, that in the ordinary run evidence on this point. The concluding section of this of years those not characterized b any unusual variation paper will be devoted to a review of the literature and in the number or area of spots ti! e annual deviations in evidence thus far available bearing upon the relation the mean annual temperature may be sufliciently uniform between sun spots and terrestrial temperature.

Unauthenticated | Downloaded 10/01/21 06:18 PM UTC hum=,iszi. MON'I'HLY WEATHER REVIEW. 67

SUN-SPOTS AND TERRESTRIAL TEMPERATURE. primarily controlled by the output of solar energy,. the mediate control which results in the day to day varia- tions is largely the result of horizontal convection whereby annual warm air is transferred from lower to higher latitudes and cold air from higher to lower latitudes. Variations of tem erature are therefore dependent to a lnr e extent upon tB e frequency and movement in lati- tud e of cyclones and anticyclones. An unusually large number of cyclones movlng due eastward in one district niay cause the temperature to be higher than usual, while the same number moving in the same direction ma cause the opposite temperature conditions in another Zstnct; hence at the close of the calendar month, when the bal- ance of temperature is struck, we do not get a true meas- phenomena- formexample,if variations in sun spots are ure of the difference between the incoming heat of insola- the cause of vanations in terrestrial temperature, that is tion and the outgoin loss of heat by radiation, but rather to say, if the two events stand in the relation of cause we obtain a residua,7 the magnitude of which de ends and effect, then the one should recede the other or at u on the activity of the latitudmal convective intercf ange least be coincident therewith. go pen' finds that the oP the month and the geographic osition of the station. heat maximum of the Tropics prece aes the spot minimum As a general theorem it may {e postulated that the by nine-tenths of a ear on the average and that the quantities of heat received by insolation and those lost interval increases wit?l distance toward the poles. The by radiation in the course of the year on the average are temperature minimum at the Equator, however, coiii- equal, for were it not so there would be progressive warm- cides rather closely with the occurrence of the spot ing or cooling of the atmosphere and the earth, as the maximum. Newcomb a found a little closer synchronism case mi ht be. but yet not so good as might be wished. The oB servational material as regards terrestrial tem- The sun-spot period it-self, commonly accepted as erature does not show permanent warming or cooling to being 11.2 years in length on the average, varies irregu- Rave occurred in any part of the globe. The observations larly from, say, 9.6 to 13.7 ears, counting from minimum do show, however, that rogressive warming and. cooling to minimum, and this adcsr another complication to the through short cycles is tB e rule, more especially m Tem- problem. KO pen in his discussion takes cognizance of perate Zones, although the phenomenon is not confined to this changing Yength of the period and has corrected the any one part of the globe to the exclusion of the remain- average terrestrial !empertttures accordingly. Mielke der. There may be as many as three separate and dis- followmg Koppen, likewise makes a correction in ter- tinct cycles of progressive change to warmer or to cooler restrial temperaturts on account of the varying length within one sun-spot cycle; if now one of these short- of the sun-s ot penod. period changes should coincide with the epoch of maxi- The muap method of showing the parallelism of the mum or minimum of sun spots, it would naturally result phenomena is that of plotting the annual variation of in an intensification of the terrestrial temperature the two events on coordinate paper and noting the extremes at that time and therefore would be considered agreements and disagreements. It is safe to sa that by the proponents of the theory as abundant justification an one who sets out to show a parallelism wilT hd of the correctness of the theory. The problem therefore suL cient resemblance, the one curve to the other, to resolves itself into a study of the short-period cycles of lead him to the belief that a real relation subsists. I ro essive temperature change from lower to higher think that it is dso true that, in general, the investi ator EvZand vice versa. is a t to slur over or disregard entirely the la5 of InJluence of diminished atmospheric transmissibilit .- par BP1elism which in m experience is at times as' ro- Diminished atmos heric transmissibility must red uce nounced aa is the resemr3 lance of the two curves. Tfere the amount of soarP energy .received at a0 earth's is also to be noted an apparent disinclination to investi- surface and in this way serve, in part at least, to lower gate close1 those cases of maxima and minima of tem- the tem erature of the atmos here. In his studies on perature w&ch are not in accord with the theory of solar solar rai iation, Prof. Kimball 1as noted that there were o in through sun spots. marked diminutions in atmospheric transmissibility in %jicu&y of disentangling the sun-s ot injuence >om the years 1884 to 1886 and in 1903 to 1904, that were tht of the general and secondary circ& tion.4-e need undoubtedly connected with violent volcanic eruptions' have but a short experience with the daily weather and that in 1891 and 1907 less marked diminutions maps of the cold season in Temperate Zones to discover occurred which have not been connected with phenomena how tremendously important as a temperature control of volcanism. Since the above dates do not coincide is the secondary atmospheric circulation. The out- with the epochs of sun-spot maximum or sun-spot features of this control are: (I) It is apparently minimum it will be of interest to see whether there is a both ep emeral and fortuitous, the c clone serving to lowering of the tem erature on the years in question. elevatestan&Yl the temperature during a perio B of not to exceed The tem erature at Eatavia was depressed in each case a day or so, over an area that may range in estent from except ti at of 1891, when there was a pronounced a few thousand square to the size of one third of the maximum. There was a very general depression of the North American Continent, and the anticyclone in turn temperature in 1903-4 in various parts of the world, serving to de rem the by-the same amount articularly in the Tropics. The curves for Batavia, over an equaY area; terrestrial temperature is Eavana, and Are uipa show the depression very dis- tinctly, but the I3onolulu curve shows a maximum 1 Yet. Zeit VLII: 241-248; XV: 279-2s' YXSI: 140-150. :Newcorm$ S Trans. Amer. Phil. SOC ' 2.1. a MielLe, J&.,~)Archiv.der Deutschen #wwarte No. 3,1913. 1 Kimball, E. E., Solar Radlsth, BuL, Mt. We&, Ob., 1910, vol. 3, p. 117.

Unauthenticated | Downloaded 10/01/21 06:18 PM UTC 88 MONTHLY WEATHER REVIEW. E'EBRUAFtY, 1991 instead of a minimum. The curves'for the five different Considering the curves of fig. 2 for the Northern portions of the United States show confirmatory as Plateau, this district bein represented by observin well as conflicting evidence of the reality of a fall in stations at Baker City, Cfreg., Boise, Lewiston, ani temperature being caused by diminished atmospheric Pocatello, ; and S okane and Walla Walla, Wash., transmissibility for solar radiation and less diminished it is at once observed tR at the temperature rose from a for earth radiation. As has been previously shown in this low value in January, 191f3, to a point 2.4O F. above paper, a cycle of temperature chan e from minimum to normal in April, then fell to 5O below the June normal, minimum is completed in about t%ree years, the time rose again to a point within 0.8' of the normal in Sep- being slightly longer in the Tropics than in Temperate tember and then again descended to a point 4.8O below Zones and being longer in some parts of tem erate zones the nornial in December. During the year 1916 there than in other parts. The latter fact, coupP ed with the were therefore two each distinct rises and falls in tem- additional fact that the short-pariod temperature oscil- perature, each one being accomplished in about three lations are soonest completed in those regions which months. The march of the temperature for the lower come most directly under the control of the secondary Lake region, the dashed curve, is similar in some res ects circulation, seems to tie up the occurrence of these and different in others. Starting at a point 2O F. ail ove short-period variations with terrestrial causes. normal in Ja.nuary, the course is downward instead of If the causes were estru-terrestrial then it shoulil be upward, as in the case of the Plateau. For the three expected that there would be greater uniformity in the months at the beginning of the year the march of the various arts of the globe. temperature in the two regions is in an opposite sense; 1Mon.tK .&y temperature cariations $IT fir0 district.? ,in. t7ie. beginning in June, however, the temperature begins to United States. -Tho mont,hly variation in tempern t,ure, rise in both regions and rises about the same amount above and below the normal, nfforcl the most convenient in both. In the Plateau region the temperature at the material available for study. I will now consider the beginning of the rise was de ressed below the normal a mean annual departure for two districts in t.he. United greater amount than in the Eake region and as a conse- States, first, the Northern Pl;it.eau, comprising witliin it.s quence the' latter passed to a point about 2O above the boundaries the'eastern portion of the States of Washing- normnl while the former did not reach the normal. ton and Oregon md all of Iildlo. The second region 1s A fall in temperature then sets in, whic.h reached a that of the Lower Great Litkes. I have compiled from ni.zximuni in the Plateau region in December and in the Table 1 of the bforVTHLP WEATIIERREYIEW thc monthly Lake region in t,he followin February. In each case depwtures of mean temperature for these two ilihcts there was a short recovery fo9 lowed by a second depres- for the years 1916, 1917, tint1 191s sepuraitely, and present sion. Note here t,liat the oscillations are now out of the smoothed means in Table -4 helow. 'fhe smoothing ste by two months. was rtccomplislied by t.he formula (a + 3b + c). TIlc geginning on the Plateau in March, 1917, temperature 4 began to moderate and continued its upward trend until means ha.ve been plotted to form the curves of test thg following December, when it had reached a point figure 2. about 7O F. above the normal for that time of year. Meantime the temperature in the Lake region was falling at. about the same rate that it was risin on the Plateau. The greatest depression, almost So beowK normal, was 6 reached in December, 1917. In both cases the results is noted were general rather than local, high temperatures 8 prevailing over t.he whole of the Plateau and Pacific 8; coast regions md it was generally cold east of the Rocky Mountains. Curiously enough the previous month of November, 1917, had been unusually warm west of the Mississtpi. In it was the warmest Novem er in 35 years. The obvious esplnnation is that in the warm month I c of November, 1917, the pressure distribut.ion gave 6 souther1 winds over lar e areas. If these winds had 7 ifor only n few %ours their effect would have -- gzzk3t in the monthly means, but ersistin as they did for dn s at a time the effect upon t%I5 e mont y means Fia. 2.-The monthly aud annual march of the tern erature in the region 01 the Lorer Lakes and the Northern Plateau &iring 1916-1911(. remains Por all time. In November, 1917, the warm - mont,h, the centers of anticyclones followed two fairly TABLE4.--Monthly mean tnnperature departures (smoothrd) for the well marked routes, viz, (1) eastward from the Pacific Nmkhsrn Plaiectu and the Lower Lakes. resperti~~ly(OF). across the States of Washington, Oregon, Idaho, and Jan. Fcb. Mar. Apr. Wiy.l , and thence southeastward toward the Gulf of I I 1-1 1 Mexico, and (3) east-southeast from about north latitude Northern Plateau. 55O, west longitude looo, to the and passing thence east-southeast from the north of the Lakes to the Atlantic States. In the cold month of December, 1917, the centers of nnticyc.lones were conc.entrated in one main group, which Lower Lakes. entered the United States from the Canadian northwest by way of the Missouri Valley, which they followed until the middle Mississippi Valley was reached. From that 1016 ..... 2.1 I 1.8 3.8 1.3 1.3 1.3 2.2 2.4 0.9 0.4 2.0 24 0.0 2.4 5.2 3.7 I 1.01 0.81 3.1 I 67 I gig I 5.a?: oint there was more or less spreadin of the paths, some :::k:::j 7.51 L.~I 2.0 1 2.0 1 1.5 I 0.6 I 0.7 0.4 1.8 0.3 yeading directly to the east and ot% ers to the Gulf of IIIIIIIIIIII Positive departures are given in tull.race type; negativas, in ordinary type. Mexico. There was this characteristic difference, vis, a Unauthenticated | Downloaded 10/01/21 06:18 PM UTC FEBRUARY,1981. MONTHLY WEaTHER REVIEW. 60 much greater southerly component of motiou in the paths of In general, there is good correspondence between the anticyclones than in the warm month. sun-spot curve (if the reader will mentally invert it the The foregoing is but a single example from many that agreement niny seem clearer) and the curve showing could be given to show that the temperature control, in dpvintioiis of tenipernture from the normal. The spot temperate regions at least, rests largely with the sec- minima of 1SS9.G and 1901.7 are both associated with ondary circulation. There are, of course, other features 1111 upprecithle rise in the lemperature. There is also of the local weather conditions that contribute lar ely a distinct lowering of t>he temperature roughly syn- to the magnitude of the observed temperature anomtfies, chronous with the spot inaxima of 1883.9, 1594.1, and as, for example, the presence or absence of clouds, the 1917.7. The most discordant result is the failure of the presence of absence of a snow cover. Moreover, oro- temperature to reach 2 mmximum in 1913.7. It will be ga hic barriers serve to accentuate and localize clinuitic noticed that hat1 not there been a drop in the tempera- drences; thus in a sense the large diflerences in tem- ture in 1913 there would probably have been a maximum perature between the northern Plateau and the region in 1913. of the Great Lakes previously described were due to the resence of the Rocky Mountains. In the one case, geeember, 1917, the movement of cold air from north to south took place along and to the east of the Rocky I Mountains, while in the other case, November, 1917, the Departures. Departurea. Depsrtures. air movement was almost wholly from the WSW. After Yesra. crossing the mountains it was warmed by the descent to Actnd. S~iioothed. Actual. ,Smoothed. lower levels, and the skies became clear, thus errnitting __ -I--- 1SS6. ..i -0.6 -0.1 IS95 ... 0.S 0.3 1909.../ 0.2 8.5 unhindered insolation. The percentage of cP ear sky- 1S87...I 0.1 -0.2 " 1899.. . 0.5 1910. .. 0.9 1 0.7 sunrise to sunset-in November, 1917. the warm month, 18 SS... -0.4 0.0'1900... 0.9 1911 ... 0.9 0.5 1669 ... 0.7 ' 0.4 1901 ... 0.6:::I 0 8 1912 ... -0.6 0. I was as high as SO per cent in eastern Montana, while for 1590 ... 0.7 0.5 1902 ... 0.4 0:3 l1913...~ 0.7 i 0.3 the same place in December, 1917, it sanli to 20 per cent. , In the last-named month the cold was dou1)tless in- tensified by a great snow blanket which orerspread the entire area north of ltttitude 35'; in tlie Valley ttntl the Lake region the snow corer lasted well into Fehru- ._.__ __ -~ ary of the succeeding year. It may well be that this Positive departures are pven 111 full-face type; netptire in ordinary type.

FIG.3.-Smoothed temperature departures. United States a'i a whde, comp.%redn ith \moothed sun-spot numbers, It-1919. great snow blanket was itself R factor in perpetuating It, has been suggested that the lowering of temperature and possibly intensifying anticyclonic conditions. once in 1915 at ti time when the normal expectation was for these were established, as in.the cold winter of 1917-18. rising temperature may have been due to diminished In this connection see the account thereof by hir. Day a tinospheric transmissibility, which in turn was condi- in the &fOlGTIlLY mEATHER REVIEW'. December, 11)18, tioned in part, at least, upon the prevalence of dust in 46570. the higher levels of the atmosphere.' The foregoing paraga hs illustritte the lack of iini- It must be admitted that exce t for the dip in the formity with respect to tK e progressive changes of tem- temperature in 1915 there is gooB parallelism between perature in two not,-wiclely separated regions. the partial the two curves if we invert the sun-spot curve. It control by climatic barriers, and especially tlie dominmt seems to be highly important to examine closely the control of the secondary ciyu!ation at all times. world-wide temperature distribution of 1912. To do Anniral tPrnpcratui-e 1:arzotwns duriml thrw sun-spot this we have but to refer back to Table 3. cycles for llnitd States as a iidd~.-I have computed the This tnble shows that for 1912 there was a pronounced mean deviation of the teni erature from the normal for excess in the temperature of the Tro ics, a smaller excess the United States as a whoP e for each year from 1886 to in the zone between 20" and 30' R orth latitude, and 1919, both inclusive, and present the actual itnil the thence. northward to 60" N. the temperature was below smoothed means in Table 5, nest below. The sniootliecl the normal, in the etistern half of the zone, amounting deviations have been plotted to form the lower curve in to 0.6' C. As has been previously observed the absolute figure 3. The curve at the top oI this figure represents innximum of the entire term of years at Habana was the smoothed sun-spot numbers of Wolfer divided by 10 reached in 1912 and the absolute maximum in Louisiana in order to bring them within a magnitude suitable for 1 Rimball, Prof. H. H., Bulldin Mmnt Weather Obsersatory, 1912, 5:161; Yo. plotting . WEATHERREV., Jan.. 1913,41:153. 41734-21-2 Unauthenticated | Downloaded 10/01/21 06:18 PM UTC 70 MONTHLY WEATHER REVIEW. REBRUARY,1921 wm reached the year previous. Referring to tlie record be shown that there are years of general high temperature of this year (1911) it, is found that the variations in the in ad1 parts of the globe, there are others that are generally Tropics were small and negative, t,hat.in the zone bet.ween cold, and st,ill oOhers in which the areas of posit,ive and 20' and 30" North the tem erat,ure was normal and that, negative departures are almost equal to each other. it was above normal in a1P zones farther north escept Although some compensation may appear in the last case, that one between 50' and 60' North 1ntit)ude. It t)hus there is no known means of proving that supposition. appears that the zonal dist,ribution of high teiiiperat,ure It has been shown in this discussion, moreover, that a was disturbed more or less locally in 1911 by low tempera- t,empe,raturedistribution of exactly tlie opposite character tures, especially in the Canadian northwest., mcl that, t,he may prevail in hwo not widely separated regions. It is distribution over Europe was even more irregular, RS the universal experience in those regions where the tem- ma be seen from Table 3. perature distribution is best known, that a mixed dis- Sxarnining, now, t'he t,em erat,ure curves for Ne,w Eng- tribution-some regions positive and some ne,oative-is land, Minnesota, etc., it wil be noted that, a. pronounced t,he most, probable one, and also that as the size of the depression of the temperah-eP occurred in the year 191I area imreases t,lie less is the probability that the tem- in three out of the five clistrict,s, beginning first in Minne- perature will be, without except,ion, above or below the sota and being followed by Colorado and last, by Louisiana. normal over bhe entire area. It seems lo ical, therefore, This may be int,erpret,edsome.w1iat8 as follows: In 1011 at to assert, that' t8hesame rule must apply w7 ien world-wide a time when world-wide t,einperat,ureswere: rising. nnd the t8eniperat8ure distribut,ion is considered and that only at temperature in the United St'ates lind been cont,inuously wide intervals should we expect complete and definite above the normal for six consecutive years, there set in, evidence of the efl'ect of some cosmical cause. at first, locally and not absolut,elyunbroken :I swing of the It is useless t,o look in the Temperate Zones for evidence temperature t,oward the other est,reme. The chrtnge. in of changes bliat, niay be due to ext>ra-terrestrialsources. the United St.a.t,eswas first not,ecl in t,he nort.li Pa.c.ific What., therefore, is most needed at the present moment Coast States for January, 1911. In the following 1nont.h is a critical analysis of esist,ing temperature observations it, had overspread the whole of t'lie Pacific Con.st St8at'es in the Tropics: the long series should be reduced to a and the Plateau region west, of the Rocky Mountains and pei.fect,ly homogeneous series and a few more first-class subnormal temperataurecont,inued over hhis entire region observatories should be established in bot,h hemispheres also in April, May, and June. The first half of the year near the Equator. also showed temperature below t,he normal in Atlantic CONCLUSIONS. Coast Stat,es,beginning in New En land in February- and (1) The n1e.m t,enipertxt.ure,,whether of n week, n month, overspreading the middle and soutf i Atlantic States dur- ing March and April. Apparent,ly this eastern depression one or more years, is in practically continuous oscillation of the temperature was ent,irely independent of the west- u and down of varying magnitude and duration. ern depression. The latter persisted practically tlirough- Ttese oscillations are oft,en concurrent over large areas out the year with a culniiiiation of the cold in November, of tlie enrt,h's surface; they may or may not be in the in which month the temperature was consist'ently below same sense. the normal escept in tlie Florida peninsula and in southern (?) At,tempts t,o discover t,he len th of the period of . Since those regions are the most, remot'e from oscillation have genernlly shown t,7 1a.t the oscillations the influence of the secondary circulation, this esception 0cc.w and recur, n parently without 0rde.r or in any is easily understood. The evidence of t,he year 1911 d0e.s systematic way. TRe bulk of the evidence points to a not support the idea that there is a progressive spreading period of bet,ween t,hree aiid four years, or the third of a of the abnormalities of temperature from one region to sun-spot cycle, as being t,liat the most commonly ex- another re ardless of orooraphic bwriers, but ra.ther that, perienced. the spreaf is from iiortyi t,o sout,li witchin the c!limatic THE SUN-SPOT CYCLE. province. (3) It is generally recognized that c.hanges in the It may be accepted as a fundamental propositZionthat, annual mean temperature in the Tropics run relatively long-continued high temperature is provocat,ive with changes in t$e spot,tedness of the sun; that t Eare heatalle1 of a change to the other extreme; in other words, that t,lie maximum in t,he Tropics is associated with the epoch of tendency is always toward the normal. There me, of spot minimum aiid that the temperature minimum is course, important esce tions to tlie rule, as when high associated wibh the epoch of spot maximum. There is, temperature and drouaK ty conditions prevail for several however, a lack of s nchronism in the variations' in sun months, but in genera? the rule holds. As a forecast'ing s obs and t,errest.risi? t'emperatures which si1 gest,s that precept it is utterly useless because t,liere is no way of t,fi e t,wo events may not stand in the relation oEi cause and telling in advance when the abnormally warm period will effect but t,hat both event,s may be due to a common, at come to an end. present' unknown, cause. The mechanism whereby the change from 1iighe.r to (4 The temperature variations in the United States, lower temperature is brought about is evidently through east, of the Rocky Mountains and above North Latitude the ressure. For some reason not yet clearly perceived 40' are so direckl controlled by the secondar circulation the Peakage of cold air from hi her to lower 1atihde.s is as to render fut,i9 e any att,empt to forecast t K e character greater and more easily acconipk ished in some yeass t,liun of the season in advance. On the PacXc coast and in the 111 others, and it is said of those years in which the le,akage zone south of North Latitude 40' the outlook is more is great that it is clue to an intensification of t,he great ho eful. continental ant,icyclone that overspreaks the continent, f5j The amplit.ude of the variations in terrestrial of North America to tbe northwest of Hudson Bay. A11 temperat,ure that may be due to sun-spots is small, less of this is er€ect,ly true, yet we are still no nearer t80n t,han 1' 0. on the average in the Tropics and diminishing solution oP the problem. thence toward the poles. In the United States, as shown The idea that there is a sort of compensation in the in Table 4, the range from the year of highest temperature annual temperature disbribution, nome regions having at sun-spot minimum, 1900, to the year of lowest tem- positive anomalies which are offset by negat,ive anomalies perature in a year of spot maximum, 1917, amounted to 111 other parts of the globe, has not much support. It can 2.5" F., 1.4" c. Unauthenticated | Downloaded 10/01/21 06:18 PM UTC