JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. IV JULY 19, 1914 No. 13 



METEOROLOGY. — American temperatures and European rain- 

 fall. W. J. Humphreys, Weather Bureau. 



It appears to be very definitely established that the average 

 temperature over the entire earth varies from year to year, that 

 it tends to follow inversely the sun spot cycle — to be lowest at 

 spot maxima and highest at spot minima; that it is invariably 

 decreased by the presence of volcanic dust in the high atmos- 

 phere; and that actually it follows closely the resultant of these 

 two influences. 1 If then the average temperature over the earth 

 does vary, it would seem logically certain that many if not all 

 other meteorological elements, such as evaporation (increases 

 with temperature), total precipitation (equals total evaporation), 

 amount of cloudiness, thunderstorm frequency, barometric pres- 

 sure, total wind movement, and the like, together with all the 

 things that they in turn affect, must also vary according to the 

 same period. But in the case of natural phenomena it often 

 happens that, owing to unsuspected imperfections in the premises, 

 there are surprising differences between the '' logically certain" 

 and the ''statistically sure." Hence the above inter-relations, 

 however certain one may feel as to what they ''ought" to be, are 

 being examined statistically as rapidly as possible, and several 

 interesting results, all confirmatory of natural and simple deduc- 

 tions, have already been obtained, though the investigation as a 

 whole is scarcely more than begun. 



' Abbot and Fowle. Annals of the Astrophysical Observatory of the Smith- 

 sonian Institution, 3: 211. 1913. Humphreys, Journal Franklin Institute, 177: 

 131. 1913. Bulletin Mount Weather Observatory, 6: 1. 1913. 



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