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SOLAR RADIATION AND WEATHER STUDIES 



By C. G. ABBOT 

 Secretary, Smithsonian Institution 



(With Three Plates) 



INTRODUCTION 



Many years ago the late Secretary Langley expressed the hope that 

 the studies of the Astrophysical Observatory on the intensity of the 

 sun's radiation would lead to long-range weather forecasting. His 

 hopes were encouraged when in 1903 our studies seemed to indicate 

 a considerable change in the sun's output of radiation * associated with 

 a marked drop of temperature over the Northern Hemisphere. This, 

 which now seems to have been a chance coincidence, led to a cam- 

 paign of " solar constant " determination which is still in progress. 

 It has involved the establishment of observing stations at high alti- 

 tudes in 10 different localities, 5 in the United States, 2 in Chile, i 

 each in South-West Africa, Algeria, and Egypt. Three of these 

 are now in occupation. Part of the expense of these observing sta- 

 tions was borne by the Government, but a considerable fraction was 

 defrayed by grants from Mr. John A. Roebling and from the Hodg- 

 kins Fund of the Smithsonian Institution. The National Geographic 

 Society also made a large grant which supported the establishment and 

 continuation of 5 years of the station in South-West Africa. 



After an excellent series of nearly daily solar-constant observations 

 of 12 years length became available, analysis showed that what at first 

 sight seemed chance variations of the sun's output really comprised 

 a summation of at least seven ^ regular periodicities. Although these 

 were of the order of only i percent or less, it seemed advisable to 

 see if they appeared to be associated with weather changes of signifi- 

 cance. A study of this question was made by the aid of the long- 

 term records of temperature and precipitation contained in " World 

 Weather Records," published recently by the Smithsonian Institution 

 with the assistance of Mr. John A. Roebling. 



^ See Ann. Rep. Smithsonian Inst. 1903, pp. 81-84, 1904; and Astrophys. Journ., 

 vol. 19, pp. 305-321, 1904- 



^ In the latest analysis, given below, covering the years 1920-1934, 12 periodici- 

 ties are found in solar variation. 



Smithsonian Miscellaneous Collections, Vol. 94, No. 10 



