i8 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



S 1,8 



(The numb»r near each point 

 indicates the number of monthly 

 Bieaiis includad in each group.) 



•9!*% 



■30 75 



Sunspot numbers 



Fig. 14. — Solar radiation increased by rising sunspot activity as shown by Aldrich. 



When very great sunspot groups are exactly central on the solar 

 disk, however, solar radiation decreases (see fig. 13). Again, from 

 P. 2499, I reproduce in figure 15 results of correlation coefficients 

 computed over an interval of 40 days. These show that in 1915 the 

 solar rotation, with its 27-day period, brought up changes of correla- 

 tion, between the days of solar-constant measures and the days fol- 

 lowing, which ran through a range of 50 percent in correlation. They 

 passed from -i-20 through to —30 percent in correlation coefficients. 

 Though the event is not of periodic nature, I mention here P. 3916 

 and P. 3940 which show, respectively, the sharp fall in the solar 

 constant when West Indian hurricanes or great magnetic storms are 

 reported (see figs. 16 and 17). 



6. SOLAR VARIATION AND WEATHER 



Having explored above evidence on the intensity of solar radiation 

 and on the variability of it, I now take up the subject of the influence 

 of solar variation on terrestrial weather. I will first quote from my 

 paper "Solar Variation a Leading Weather Element" (P. 4135, Aug. 

 1953) : "On January 28, 1953, the American Meteorological Society 

 devoted the day to consideration of the influence of solar variation on 



