The Rainfall of the Northeastern United States

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JANUARY,1915. MONTHTS WEATHER REVIEW. 11 eastern slopes (except in Vermont), and the eastern shores j : I. of t,heGreat Lakes et niore snow t!hnn the western. THE RAINFALL OF THE NORTHEASTERN UNITED Snow generally fa4 Is in connection with winter c.ycli’ncs, STATES. for the cyc,loiiic act.ion and the effect of to ography on the winds cause precipitation. As the norti! east wincl is Iiy B. 0. WALLIS,B. Sc. (ECONOMICS).F. R. C;. R., F. S. S. both cold and damp over prrtctically the whole e.ais .. t ern [Dated: North Finchlcp, England. Sept. 21,1914.1 United States, it is the wind of the goat snowst,orms. The northwest wind, although cold, is genernllv dry and THE METHOD OF INVESTIGATION. so brings, at most, only snow flurries esccpt, ’locnllr 011 Probably the two most iniportant considcrat,ions re- a windward mountain slope or in the lee of t,hc Grent ga.rding the rainffill of any area are its total quant,ity Lakes. In brief, the nia.in factors w7hic.h control snowfall aiid i t.s distribiibion through tho year. Attenhn is are ten1 ersture, moist-ure in the air, esposiiro to moistm called in this pn.pe.r to the second c.onside,rat,ion,and n.n winds, focnl topography, and the pnssagc of win t.cr n.tt.enipt,lins been made to measure the distribut,ion by cyclones. mmns of the statistid niothod of tlifferenccs. The REFERENCESAND NOTES. nniount of rainfall which would be prccipit>at.d n.t n (1) &e also American Almanac for 1837, p. 169.-185: “Notiim of givm plsce, upon the n,ssumpt>iont,hnt such rainfnll were remarkably cold winters.” evenly distrihu ted through the year, hss heen taken fi.s (2) Some other journals with less extensive record@are: n 7~0~)~.This nom. is obtained by dividing the total Cleaveland, Parker. Results of meteomlogiral obsrrvat.innr; matlr nnnual fall hy 365, and by niult.iplying tho quotients by at Brunswick, Me., 1S07 to 1S57. Caswell, Alexis. Resulta of meteorologicd obrervatin~isn;;id~ :it 2S, :jO, a.nd 31, respert,ively, to obt.nin the numhcrs Providence, R. I., from December, 1S31, to May. 1SBO. which rcpresent the nornis for t.he niont,li of Februa.ry, Hill, Leonard. Met.coro1ogica.land clironological register. IPDfi lo and for the 30- and 31-c1a.y mont.hs. The dueof the 1869 at Enst Bridgewater. h.iw. Plymouth, Mass. 1PIi9. norm 11a.s been tdwi for each iiionth for all places as (3) See J. P. Espy’s reports in the Journal of the Fm.nklin Indtutp, 100, so 2-5, 13-”’-3) Philadelphia. 1839 to 1811. t,liat in t,he accompmying maps (figs. , (4) See Report of the Smithaonian Institution for 1855: Directions for meteorolo ical observations, adopted by the Smiths0nia.n Institution for the ~irst-fiwotmervere. (5) U. S. Weather Bureau. Annusl report of the Chief, 1891-93. Washington, 1893. p. 147. (6) A history of meteorological ohervations in the United State8 is attempted by Marcus Benjamin in the work ‘‘The Smithsonim Institution, 18-18-1898’’ (Washington, 1697) on pp. 647-678. More comp1et.e details are gven by various authors before t,he International Meteorological Congress, held at Chicago, Ill., August 21-24, 1S93. (&e U. S. Weather Bureau Bulletin 11. pp. 207-220, 82-302. ) (7) Volney, C. F. A view of the soil and climate of the United States of America. Translated from the French by C. R. Brown. Philadelphia, 1804. (8) Blodget, Lorin. Climatology of the United States. and of the TemDerat.eLatitudes of the North American cont.inent. Embracing a full coi )arison of these with the climatology . . . of Europe and Asi: . . . Incfuding a summary of the statistics of meteorological oheer- vatious in the United States condensed from recent scientific and official publications. Philadelphia. 1857. xvi. [17]-536 4’. An appreciation of this monumental work will be founfin the MONTHLYWEATHER REVIEW, January, 1914,42: 33-27. VIG. L-Anniial mar& of,phiviornetrieeocfficients for Michiran. Ohio Valley, nnd 1.h~ (9) S. Weather Bureau. Rainfall and snow of the United Statrp Piedmont compared with the anniral march of the temperature onomnlirs for the U. oorthenstcru I’nihl Sf.ates. ascompiled tc, theendof 1891, withennua1,seasonul. monthly,and othw charts. Teat and Atlas. Waahington. 1894. 80 p. 4’. Atlas: 100 23 charta, 18 x 21 inches. the line which is marked indicates that the rainfnll This publication is reviewed in Amer. meteorol. jour., Tlcxrtnn, n.t all places along th8.t line is the norni for thc month. Mass., June, 1S95, 12: 71-2. Differenccs from the norm are cs resscd as percentages. (10) Henry, A. J. & others. Climatology of the United Ptaten. Su pose the norm for n given pace for R’aahington. 1906. 1013 p. 33 pl. 4’. (U. 8. \+‘rather Dureau F bulletin “Q.” W.B. no. 361.) inc! es, sncl the actual average rainfall at (I!) See MOXTHLPWEATI~ER REVIEW, Wa~hington, June, 1914, 43: Januniy is 3 inches; then since, when 2+==100, 3=130, 318330. the difference for tshat place for January is 130, which (12) U. S. Weather Bureau. Summary of the climatolngiral data implies that during January at that place the precipita- for the United States by Sections 106 [sertions). Printed at various 30 cent is section centera. 1908-1912. var. pag. 4’. (Bulletin “W.” W.B. tion is per above the nomi; i. e., January n no. 476.) re1ativ ely wet m ont,h . (13) Such an effect is clearly shown on the IT. 8. Weather Bureau The ntinie “ pluvionictric coefficient ” has been given “Snow and Ice Bulletin” for December 30, 1913. to t,liis qua.ntitative expression by Dr. A. Angot, who (14) For a thorough study of the physird rhaiigccl whirh take placc is responsihle for tallis application of t.hc method of in a snom-cover. See - Jansson & Westman, J. Quelques rerherrhcn Hiir In rnurcrtiirc rliff ewnces to rainfall studiss. When pluviomctric de neige. Biill., Geol. instit. of Up~ah,1901, Nn. 10, 5, pt. 2, pp. ?::I-- coefficicnts are inrlicated upon iiiaps, u 1011 the same 260. principles as isohyets, the lincs of equal c opnrtiire from (15) See MONTELY WEATRERREVIEW, November, 1911. 39: 1671; I alm Chart VIII in the REVIEWfor November, 1911. the: rainfall norni have been called by tho present writer (16) The United States Forest Service ofirial liring at an altitude ol ‘I equipluvcs,” using a Latin term for the sake of greater 5,060 ft. on Mount Pisgah, N.C., 18 miles eouthwst of Asherille, N. C., ~- rwently told the writer that the snow accumulated on the ground. 1 Mr. Ernest I;nld (I) has pointed out that the ‘*pluvlo,metrircoollicient“ is “the ratin of the illsin daily rainfall01 a particular month to the LuBan daily rninlall of the mmetimes to a depth of 3 feet, and that in one niqht a snowfall of 27 w-hole yrw.” inrhes occurred. The similarity between these extremes and those The term “isomer” ha< been suggested bv Jfr. G. Mkr (4j in place of t.he term met in eastern Massachusetts, suggests that the average snowfall in the %quiplure” coined by Nr. WdLIL. If the former term is used one should be csreful to prelaee It with !he word “rsinlall” or “precipitatim.” since in itself ‘*isomer”does southern Appalachians may be about 50 inches annually. not suggest a quality of rainfall. This disnlvantaggo Is absent from the term “equi- (17) Greely, Adojphus W. American Weather. 11. 16. p1uve.”-[c. A., jr.]

Unauthenticated | Downloaded 09/29/21 10:21 AM UTC 13 MONTHLY WEATHER REVIEW. .TAXTART? 191 ;: distainctaess. The accompanying maps show the equi- Sup ose we divide the places of which there are luves for the several mont,hs for t,he nort,heast.ern rainfa R records into three classes: ((r.) where the records enited St,ates. have been lie t for from 40 to 50 pears, (b) where the Eqzri. ~Zwtwin. eoiihnst with isof, yefs.-I t has been laid records have Eeen ke t for from 20 to 40 years, and (c) down th at monthly rclinfall maps, where the rainfall is where records have !,en kept for less than 20 years. indicnted by means of isohvets, are of little value unless When the maps are under construction, all stations in (1) the observat,ions have been taken over h. long series class (a) will be entered first, and the general run of the of years, which should approsinlate t.o 50, and (3) ob- equipluves can then be determined; stations in class

.___-._.-,-.I -..i-- -.\., J .r January. Fro. 2.--Equlpluves for the northeastern United States lor the months 01 January, Febnrarp, and March. (b) will nest be entered in all those cases whore the values are in general harmony with the run of the equipluves; and stations in class (e) will be used to determine the run of the equipluves when other observations fail. In figures 2-5 accompanying this pa Ier the “aqui- luves” are drawn at 30 er cent intcrvafs, and it rarely gappens that places in cP asses (b) and (c) cliffcr by more than 10 per cent from the general arernge vdues of surrounding places. Consequently, in nctual practice,

April. May. June. PIO.3.-Equipluves lor the northeastern United States for the months of April, May, and June. coefficient,s snioothes out the ac.c.identd rain-s lashes, most of the records can be utilized directly without. and at the same time it t,ends to brin the values o6 tnined resorting to mothods of interpolatlion. during n dry series of years into cs oser harmony with TAe utility of equiphves.-To es res5 with sonic the values obtained clurin a wet series of years. Con- precision the aspect regarding rninf aiwhich is under sequently, t,he met,hod of %ifferenres tends to allow the investigation the term “rainfall intensity” is used; and student to ne lect all interpolative calculations in order it nisy be urged that it is exactly rainfall intensity to bring his vaf ues to the average required for a constant thou hout the ear which is the most important fact period of years. regariing rainfsi, when once the average annual precipitation has been determined. See an extract from H. R. Mill on p. 24, below.

Unauthenticated | Downloaded 09/29/21 10:21 AM UTC JANUARY,1915. MONTHLY WEATHER REVIEW. 13 In another paper (1) the writer has studied tlie England that the intensit of the rainfall varies with rainfall of the continent of Africa and finds the rain- the relief of the land. derever the land is lowland, fall se uence throughout the year is related to the the annual rainfall is relatively small and the highlands are swing c?f the sun; also that the two portions of the con- relatively wet; but the wet districts have a greater tinent north and south of the Equator present precisely rainfall intensity in winter than the dry districts, while similar general rainfall features. It has further been the dry districts have a more intense r’ainfall in summer determined, in regard to the area of Africa where the than the wet districts. Assumin7 that the sequence actual annual total precipitation is heaviest, that the of rainfall intensity upon the low ands is the average

July. August. September. VIG. I.--Equlpluves for the northeastern Unlted States for the months of July, August, and September. rrtinfdl intensity is of tho same niagiiitude as ili the rainfall se uence due to the influence of the sun, then the desert where the actual recipitution is least. There effect of %e hih is to superimpose upoii tlie [average] is duo, in dl probability, Pittle difference in magnitude rainfall [sequence] due to solar influences a great escess and intciisity between the rainfall of Africa between of rainfall upon the hills during tlie colder months. At the desert ureas and the “monsoony’ rainfall of India.3 tho same time in this district of England the pluviometric In another paper (2) it has been demonstrated by the coefficients have a maximum value of 150. same methods that the continent of Australia presents similar features regarding its rainfall to those previously THE NORTHEASTERN UNITED STATES. determined in the case of Africa. Now the question The accompanying maps (figs. 3-5) have been made arises whether the intensity of the rainfall in areas from data publlshcd by the United States [Weather

October. November December. Fia. 8.-Equipluves lor the northewtern United States for the month8 of Octoher, November, and 1)ecember. outside the limits of parallels 40°N and 40’s yields Bureau] in order to investigate the rainfd conditions siinilsr features; e. whet,her the pluviometric cocffi- upon the western margin of the Atlantic Ocean in rela- cients ever reach tk e magnitude of 300 and over; tion to the results obtained for England wid Africa. whether the rainfall intensity depends niainlp upon Figure 1 is based u on these ~iiys.It qives the rainfall the dtitude of the sun. results in a generaP way and in icatos t iut the rainfall In a third paper (3) it has been pointed out in the on the whole “swings with the sun” and that the main case of the district of the Southern Pennines in northern effect of the uplands between the Ohio Valle mid the .~ ...... - ...... Piedmont is to bring the rainfall sequence of t ze lattc?r a a See an extract from the author’s paper (1). reprinted on p. 24 below. nioritli later in the year. The linc; inarked “uno~n~tlous

Unauthenticated | Downloaded 09/29/21 10:21 AM UTC 14 MONTHLY WEATHER REVIEW. JANUARY,191.5 tem eratures,” which is based upon a series of ma s area previously described, and the rainfall of the whole ubEs ‘ hed in paper (1) indicates for this portion of & area is now considered in a broader view and with less bnited States the amount of variation, month by month, detail than was from the average temperature round the world in similar The method of c latitudes. This average temperature in similar latitudes measures ztir temperatures as a function of latitude; varia Lions from average temperatures-i. e., from the accompanyin maps and diagrams (figs. 6-23). anomalous tem eratures-indicate the local temperature It should be noted, kst, that the range of the rainfall variations of tI? e United States due to the effect of the intensity is much greater in the area now considered sun upon the area of the northeastern United States. than in the northeast alone. The minimum value of Consequently Sgure 1 shows that the rainfall of this the pluviometric coefficients is less than 33 and the maxi- area depends (1) upon the elevation of the sun, and (3) mum is between 200 and 233 which gives a range of 200 upon the world position of the area in particular refer- equivalent to one-sixth of the total annual precipitation. ence to tho swing of the sun. Figures 6 and 7 indicate In the northeast corner the range extends from 70 to the areas of differences in the driest and wettest periods, about 150, and is less than 100, i. e., less than the rainfall respectively, and give a spatial meaning to the facts norm for one month. A eneral survey of the twelve shown in figure 1. monthly equipluve maps (8 gs. 12-23) at once forces the Consideration of the twelve monthly maps resented conclusion that, in general, the rainfall gradient is from by figures 2, 3, 4, and 5 leads to a division of t% e north- northwest to southeast, for the majority of the e ui- eastern United States into four rainfall regions-(1) the luves run from northeast toward the southwest. &is northeast corner which beam little relationship to the fact was suggested by the conclusions reached in the remainder of the area and can be omitted from further above communication. consideration; (2) the Lake region and Michi an on The niain features of the intensity of preci itation may the north; (3) the Ohio Valley area in the mid e, and now be considered month by month. P n January (4) the Piedmont and the Coastal area on the southeast.w (fi . 12) rainfall slightly above the norm occurs in the It is convenient to begin the examination of the maps vaK leys of the lower Mississippi and the Ohio; to the with the month of September. In that month the north southeast and to the northwest the intensity of rainfall (2) and the coast (4) are of average wetness, but the Ohio diminishes. In February the area of rainfall above the Valley (3) is relatively dry. In October the dryness is norm has extended toward the coast and in Alabama and more extensive and reaches almost to the southeast [the Georgia the rainfall is most intense; elsewhere there is South Atlantic] coast. In November the dry conditions little change from Janua In March, exce t for an have moved still farther eastward. In December the increased intensity in the Xakotas and along t Ee coastal rainfall is very little removed from normal (100 per cent) lowlands near Chesapeake Bay there is slight change from everywhere. In January the Ohio Valle is wetter than February. the neighborin hills, and be ond the hdthere is a still In April, west of the Mississippi, the rainfall is above drier rep. fn February ti e coastal lands are wet and the norm, and the area east of that river tends to be drier. the nort is &y. In March the Ohio Valley shows signs In Ma there is a marked increase in the intensit of the of eater wetness, which persists during April. rainfd especially in Oklahoma and South 6akota- May the north is the wettest regon; this relative in general, the intensity of the rainfall increases with thd wetness spreads eastward by June and becomes more distance from Florida. In June the southeast coast States intense b July. In August the wetness has reached the and the northwest States show a marked increase in in- coast. !&e maps, therefore, give a s atial significance tensity; from the Dakotas to Kansas, the rainfall is at to the conclusions previously state$ which may be the maximum for the whole area, the fall in June being generalized thus: A wave of dryness moves south- equal to twice the norm. Alabama has the least intense eastward during the period when the temperature is rainfall and the month in general is the exact opposite falling, from September to the end of Januar , and a of January and February. wave of wetness moves southeastward during tK e period In Jul the whole intensity seems to have moved when the tem erature is rising, from May to August. toward t1 e northwest, the coasts are wetter and tshe The rainfalP of the northeastern United States is a northeast is drier than in June. In Belt I (fig. S and 9) the function of its latitude and its position on the western rainfall intensit “swings with the sun,” and the farther margin of the Atlantic Ocean. away the land ‘e4 from the ocean, the more precisely is this fact true. B About the seasons of the equinoxes the rainfall is the norm, at midwinter low, and at mid- summer it is high; the pluviometric range is very large. i 11. In Belt I1 (fig. S and lo), in general, the pluviometnc ran e \ is lenst; the most striking feature of the diagram is t %e THE DISTRIBUTION OF THE RAINFALL IN THE way in which the a hs interlace. On a very small EASTERN UNITED STATES. scale the rainfall of t%?il ‘s elt varies with the “swing of the By B. C. WALLIS,B. Sc. (Economics), F. R. G. S., F. S. S. sun.” The whole of this belt is marked by a compara- [Dated: North Finchley, England, Nov. 24,1914.1 tive steadiness of the precipitation throughout the year; it forms a strikin illustration of the phrase “rainfall at In the receding pa er the sequence of the intensity of all seasons.” In 5elt I11 (fig. S and ll),the luviometric the rainf E& was descrii! ed in reference to the northeastern ran e is intermediate between those in the otE er two belts corner of the United States. This area includes the major an the distribution of the rain is unequal. From Novem- portion of the industrial area of the United States and is a berB to July, i. e., about two-thirds of the year, the rainfall region of diverse farming operations; in the present com- intensity increases by two stages which are separated by munication the area which includes the cotton belt and the a sli ht fall near the sprin equnox. The intensity drops greater portion of the wheat belt has been added to the sudf enly from August to% ovember.

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