26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



Study of the sun-spot relations, no doubt holds in the case of solar 

 radiation changes of shorter period. 



In order to study the seasonal shift in the centers of action, the 

 data given in table 3 were plotted in a series of charts. It is not 

 feasible to reproduce all of these charts, but they indicate that the 

 centers of action for each intensity of solar radiation oscillate around 

 their mean position as a result of seasonal changes. Hence, in order 

 to determine the effect of any solar radiation change, both the solar 

 intensity and the seasonal change must be considered. 



In figures 23, 24, 25, and 26 the differences between the mean 

 pressures for solar intensities of + .006 to + .010 and — .006 to — .010 

 are given for each season. The mean change in solar radiation is about 

 .015 calorie or 0.8 percent of the normal value, 1,940 calories. These 

 charts show the direct effect of this change of solar radiation on the 

 pressure as nearly as is possible with any arrangement of the data at 

 present available. The changes shown by these charts are not small. 

 They are sufficiently large to dominate the weather and to make their 

 consideration imperative to anyone who would understand the weather 

 and its causes. 



The points of interest to be noted in these charts are : ( i ) With 

 increased solar radiation there is a fall of pressure between Australia 

 and Africa in December to February, when the sun is south of the 

 Equator, and a fall of pressure between Malaysia and the West Indies 

 in June to August, when the sun is north of the Equator; (2) with 

 increased solar radiation there is a marked fall of pressure at all seasons 

 in the North Atlantic, more marked and farther north in winter and 

 spring and less marked and farther south in summer and autumn ; 

 (3) there is also a fall of pressure in the North Pacific west of North 

 America ; this area of fall is farther north and more marked in winter, 

 but less pronounced than in the North Atlantic; (4) there is an 

 increase of pressure over the Arctic region of North America at all 

 seasons, although the center of greatest increase appears to oscillate 

 back and forth across the continent; (5) there are two centers of 

 increased pressure in northern Eurasia, one of the centers being found 

 over eastern Asia and one between western Siberia and northern 

 Europe, both showing large seasonal oscillations ; (6) there are centers 

 of increased pressure about 10° to 30° N. ; one of these is found 

 at all seasons between Hawaii and Mexico, another is in the Pacific 

 about 140° E., and other more transient areas are near the west coast 

 of Africa and near India. The stations in the Southern Hemisphere 

 are too few to enable one to follow the shifting of the centers of action. 



