proceedings: Washington academy 241 



Dr. C. F. Brooks, of the Weather Bureau, referred to the difficulty 

 which positive and negative correlations occurring at different seasons 

 introduce into any attempt to use solar variations in forecasting. In 

 a lecture before the Academy in 1918 Nansen^ showed how surface 

 temperatures at different places on the earth varied either directly or 

 oppositely with the sun spot numbers, and how the direction of varia- 

 tion changed from time to time, due evidently to shifts in the centers 

 of action of the atmosphere. There are "fixed" centers of action, as 

 at the Azores, which control seasonal weather; but it is the moving 

 centers (the high and low pressure areas) that control our weather from 

 day to day. If the actual positions of Highs and Lows be taken into 

 consideration, we may find it possible to predict whether a given varia- 

 tion in the solar constant will have a positive or negative result at a 

 particular place. Increasing the strength of a High, for instance, would 

 have opposite effects on temperature at stations on the east and west 

 sides of the High. 



As an example of a probable correlation between solar and weather 

 phenomena, the speaker called attention to six successive recurrences 

 of abnormally high pressures somewhere in the United States or Canada 

 in the fall and winter of 1917-1918; these recurred at about 2 7 -day 

 intervals, or about the synodic rotation period of the sun in low lati- 

 tudes. The maxima occurred, however, at different places. 



The time is perhaps not distant when the weather forecaster, having 

 before him the existing and expected locations of the Highs and Lows, 

 may be able to use solar constant data to predict most of the now in- 

 explicable changes in the intensities of those centers. 



Dr. L. A. Bauer, of the Department of Terrestrial Magnetism, Car- 

 negie Institution, made special mention of the achievement of the 

 Astrophysical Observatory in introducing new methods that so greatly 

 diminished the time and labor of obtaining solar constant data. He 

 hoped that a continuous record of the solar constant might some day 

 be possible. 



Dr. Abbot stated his gratification that all the speakers had agreed 

 on the need of additional stations to obtain more and better values 

 of the intensity of solar radiation. The data available to Clayton were 

 far from being completely satisfactory, for the measurements were 

 frequently interfered with by cloudiness at both Mt. Wilson and Calama. 

 Nevertheless, he believed the correlation of the radiation and temper- 

 ature observations too striking to be avoided, whatever the theoretical 

 application may be. Dr. Brooks' suggestion regarding the movement 

 of action-centers may well account for Clayton's varying correlations. 

 In reply to a question by Col. T. L. Casey he pointed out that the 

 average value of the solar constant has not changed in the right direc- 

 tion to account readily for the great difference between the winters of 

 1918-19 and 1919-20 in Washington, but that the weather depends to 



1 This JotTRNAL 8: 135-138. 1918. 



