NO. 6 



SOLAR RADIATION AND WEATHER CLAYTON 



39 



That the pressure in the equatorial regions is lower at all times of 

 the year with the increased solar radiation which Dr. Abbot' has 

 found at the time of maximum sun spots is evident from an examina- 

 tion of figure 32. The upper chart in this figure shows the mean 

 annual excess and defect of pressure for the years around sun-spot 

 maximum as contrasted with the mean pressure of the years around 

 sun-spot minimum. The middle chart shows the differences -found in 

 the same way for the three months of winter, while the lower charts 

 show the difference for the three months of summer. In each case 

 the pressure is lower at maximum sun spots in the equatorial regions 



SUNSPOT PERIOD - RAINFALL. 



180 160 140 120 100 80 60 40 20 O 20 40 60 80 100 120 140 160 180 



80 160 140 120 100 60 60 40 20 O 20 40 60 80 100 120 140 160 180 



Fig. 33- — Shaded areas show an excess of rainfall at the time of sun-spot 

 maximum. Broken lines indicate a deficiency of rainfall at the time of sun-spot 

 maximum. Figures at end of line give percentages of excess or deficiency of 

 rainfall over that at minimum spots. 



and higher in middle latitudes. The fact that the belts of excess 

 pressures in middle latitudes are nearer the poles than the normal 

 positions of the middle latitude high pressures, proves that these 

 belts are displaced toward the poles with the increased radiation at 

 the time of maximum sun spots in the same manner as is the case in 

 the short period changes of solar radiation. 



There is also shown the same tendency in middle latitudes for 

 the excess of pressure to change with the season from continent to 

 ocean, being high over the continents in winter and over the oceans 

 in summer. The excess of rainfall within the pressure belts of the 

 tropics and over the northern oceans at the time of sun-spot maximum 

 is disclosed in figure 33. 



Smithsonian Misc. Coll., ^'ol. 77, No. 3, p. 38; World \\'eather, p. 260. 



