NO. 7 



THE ATMOSPHERE AND THE SUN CLAYTON 



13 



tudes over the North Pacific. This longitude distribution is appar- 

 ently another effect of centrifugal action developed by increased 

 atmospheric circulation with increased solar activity. In regions 

 where the air flows more freely, as over the great expanse of the 

 Pacific, the centrifugal force developed tends to lower the pressure, 

 especially in high latitudes, more over the water surfaces than over 

 the land areas. 



Fig. 8. — Longitude differences between high and low solar activity. 



The primary cause of the general atmospheric circulation is be- 

 lieved to be the contrast in temperature between equator and pole. 

 This circulation and all its attendant phenomena changes in unison 

 with changes in the amount of solar radiation received by the earth, 

 just as the regulator on a steam engine varies with the amount of 

 heat received by the boiler. 



Once in operation there are at least four modifying forces of 

 importance acting on the general atmospheric circulation : 



