May 2, 1907 J 



NA TURE 



CLIMATOLOGV OF THE UNITED STATES. 



PREPARED by Prof. A. J. Henry, under the 

 direction of Prof. Willis L. Moore, chief of the 

 I'nitcd States Weather Bureau, a volume ' of 1012 

 pat;cs has recently been published dealing with the 

 climate of the United States. This most valuable 

 contribution to meteorological science will be 

 welcomed by all who wish for the advancement of 

 this subject, and the Department of Agriculture is 

 10 be congratulated on publishing in this form the 

 climatic statistics for the different portions of the 

 United States. 



Americans are nothing if not practical, and the 

 issue of the volume before us is an excellent example 

 of this. Thus, in the introduction, we are told first 

 that the " need of such a volume has been felt for 

 some time, particularly within the Department." 

 Further, and this is where Great Britain might take 

 a hint with regard to furthering the agricultural 

 needs of her colonies, " During the last few years 

 the Bureau of Plant Industry has introduced a 

 number of seeds and plants new to this country, as 

 ^vell as new varieties of plants and grains already 

 well established. In order that the best results may 

 be obtained, it is essential that the new plant or seed 

 be placed in a climate closely resembling that of its 

 original habitat. The Pomologist has likewise felt 

 the need of more generalised climatic data than is 

 afforded bv the scattered publications of the Weather 

 Service, and this is true in other lines of research 

 that are being prosecuted by the Department." 



The above quotation is another instance, if one is 

 required, that the .Xmerican Government carefully 

 fosters the study of meteorology, and thereby in- 

 creases its revenue. 



The data on which the statistics here given are 

 based may be said to be taken from three sets of 

 observations. Thus the first is due to the Medical 

 Department of the Army, the observations being made 

 .-It military posts during the period 1820-1890. The 

 second is the result of observations made by the 

 cooperating observers of the Smithsonian Institution, 

 and extends from :S49~i874. The third and last set 

 is due to the Signal Service and the ^^■eather Bureau, 

 and commenced in 1S70 and is continued up to date. 



In spite, however, of the fact that several records 

 cover a great number of years, only a few records 

 exceeding fifteen years in length are inserted in this 

 volume. The reason for this, as stated, is that it is 

 only within the last ten or twelve years that 

 uniformitv, both in observing and recording climato- 

 logical data, has been attained. . 



The book before us may be considered as divided 

 into three sections. The first portion consists of an 

 .admirable summarv of the main features of the 

 United States climate (pp. 7-S4), supplemented with 

 numerous maps and charts. The second part (pp. 

 S5-11S) consists of general tables of temperature, 

 humidity, and wind, followed by a list and map of 

 the climatological stations which appear in the rcjxirt. 

 The remaining but greater portion of the volume 

 (pp. 1 19-1012) is composed of the contributions of the 

 district forecaster or section director of each State. 

 This, as a rule, takes the form of a general descrip- 

 tion in words of the climate of the State as a whole, 

 then a State summary in tabular form regarding 

 temperature, frost, and precipitation, and, lastly, the 

 monthly, seasonal, and annual means for temperature 

 and precipitation for each station, together with such 

 data as description of localitv, instrumental equip- 

 ment, and positions of instruments. \\'hen it be 



1 "Ciimatolngy of tli.^ United States." By A. I. Henry. U.S. Depart- 

 ment of Agriculture. Weather Bureau, Fulletin Q (Wa>hington, ic)o6.) 



NO. 1957. VOL. 76] 



mentioned that no less than 6go stations are referred 

 to, and the data for each station occupy a page, some 

 idea of the amount of material dealt with can be 

 obtained. 



Reference has been made above to Prof. Henry's 

 admirable summary of the broader features of 

 -American climate. This portion of the work should 

 be read with great interest, because it brings together 

 in clear and concise language an account of the 

 general conditions of atmospheric circulation which 

 occur over this large stretch of country. Justice to 

 this essay could only be done by occupying consider- 

 able space, so remarks v.ill be limited simply to one 

 or two points which seem to be of more special 

 interest. The first of these describes the conditions 

 which accompany "cold weaves," which occasionally 

 pass over the country and envelop it in .Arctic weather. 

 The fall of temperature to justify one of these waves 

 must, as is stated, be at least 20° F. in twenty-four 

 hours, except along the Gulf Coast, where a drop 

 of 16° F. or more constitutes a cold wave-. Cold 

 waves follow in the wake of cyclones under the 

 influence of which the temperature has risen. The 

 lowest isotherms are nearly coincident with the 

 highest reading isobars in the anticyclonic system 

 which follows the cyclone. The i.sotherms, other than 

 the lowest, onlv very generally follow the trend of the 

 isobars, and spread much further south over the 

 United .States than the isobars would suggest. The 

 cause of these cold waves Is due, not merely to the 

 ]jievalence of the cold north-west winds which follow 

 the passage of the low-pressure area, but more par- 

 ticularly to the radiation from the ground in the 

 clear dry air in the rear of the cyclone. The cold 

 of radiation is communicated to a greater stratum of 

 air, and the effect of solar radiation is reduced, since 

 the surface layers are being constantly renewed by 

 colder air from higher latitudes. With little hori- 

 zontal air movement in the anticyclone, the night 

 temperatures are low. and there is a tendency for 

 this cold air to collect in valleys and basins. January, 

 Februarv, and March are the months in which the 

 waves chiefly occur, and in the eastern part of the 

 United States the average number a year is three or 

 four. 



Prof. Henrv gives some very instructive maps 

 iliustrating the barometric and thermometric con- 

 ditions during some of the more intense .waves that 

 have been recorded. 



Hot waves, or "heated terms" as he calls them, 

 are more brieflv dealt with, and .some idea of their 

 effect on humanity may be gathered from the state- 

 ment that " during the three weeks that ended 

 August 22, 1896, there were 2036 known deaths in 

 the" United States directly attributable to sunstroke. 

 Large as this number is, it doubtless falls far short 

 of the actual number of cases." 



In the same thoroug-h way in which the above 

 waves of heat and cold have been discussed, Prof. 

 Henry deals with precipitation, sunshine, wind (in- 

 cluding thunderstorms and tornadoes), &c. The con- 

 cluding section is devoted to seasonal variations from 

 vear to }car. It will be remembered that at the 

 beginning of the present year, when Europe was 

 enveloped in a cold wave, Iceland, with_ a much 

 more northern latitude, was revelling in warm 

 weather. Similar inversions occur in the United 

 States. Thus we read that, during the severe 

 we.ither of March, 1906, when temperatures 10° F. 

 to 20^ F. below zero prevailed in the northern Rocky 

 Mountain retrion, includinsr the southern portions of 

 Alberta, .Assiniboia, and Winnipeg, the weather in 

 .Alaska, far away to the north, was warm and 

 pleasant, with temperatures above freezing in the 



