REPORT OF THE SECRETARY 87 



Arctowski on the staff of the Observatory for 1 year, from Decem- 

 ber 1, 1939. Dr. Arctowski was asked to investigate the relations 

 between solar variation and the weather. At that time he doubted 

 the reality of solar variation as indicated by our observations. But 

 within 2 weeks after beginning his studies, Dr. Arctowski became 

 thoroughly convinced of the reality of solar variation, and that it 

 is the major factor in weather. He has announced these findings 

 in two papers.^ He is continuing his researches in this field with 

 consuming zeal. It is hoped to retain him another year after the 

 completion of his present engagement. 



With the assistance of Miss N. M. McCandlish, special computer 

 under a grant from John A. Roebling, Dr. Abbot has endeavored 

 to evaluate the separate influences produced on weather by the long- 

 range solar periodicities which are referred to above. For this re- 

 search monthly departures from normal temperature and rainfall for 

 numerous stations in America and other regions were used. It soon 

 appeared that the solar periodicities produce considerable weather 

 changes. But for periodicities of less than 25 months' length, and 

 occasionally for longer ones, shifting of phases in the weather re- 

 sponses took place from time to time. It occurred to Dr. Abbot 

 that these shifts very probably are due to seasonal influences. That 

 is, ?K. solar cause operating in winter might reasonably produce a 

 different phase in its weather effects than the same cause operating in 

 summer. Inasmuch as the solar periodicities are not commensurable 

 with 12 months, their phases of course shift through the seasons. 

 On testing this hypothesis it was found to be sustained by data from 

 many meteorological stations. 



It was then recognized that these phase effects might be eliminated 

 by taking into account least common multiples of the several periods 

 as compared individually to 12 months. For instance, an 8-month 

 periodicity returns each 24 months in the same season of the year. 

 Other periodicities recur in the same season at longer intervals. Act- 

 ing upon this basis we computed the average weather effects over a 

 century or more for 8 solar periodicities ranging in length from 8 

 months to 68 months in length. Among the stations used were Copen- 

 hagen, Vienna, and New Haven, all beginning with the year 1800. 

 It was very encouraging to find that, with the phase taken care of, 

 as explained above, all of these stations agreed in indicating pro- 

 nounced effects of solar variation, and that there is no indication that 

 a change of phase has occurred in the solar periodicities for over a 

 century. In such long series the solar influences were repeated many 



' Solar faculae and solar constant variations. Proc. Nat. Acad. ScL, vol. 26, No. 6, 

 pp. 406-411, June 1940. 



Researches on temperature changes from day to day and solar constant variations. Bull. 

 Amer. Meteorol. Soc, vol. 21, pp. 257-261, June 1940. 



