280 



THE WEATHER 



north and south with the annual migration of the sun. The 

 unequal warming of land and water modifies the general winds 

 and causes special wind movements on and about the conti- 

 nents. Over and through these are the traveling pressure areas 

 that appear in the trade wind belts in late summer and autumn 

 and in the westerlies throughout the year. In the temperate 

 zones, the traveling pressure areas cause the general weather 



FIG. 209. A winter month. 



1. High pressure in interior. 



2. Storm tracks farther south and southeast. 



3. Prevailing northwesterly winds. , 



4. Distribution of precipitation. 



changes from day to day, and, in summer, help to provide the 

 conditions favoring the formation of local storms. These 

 principal features operating together produce most of the 

 weather of earth. In many countries of the temperate zone, 

 man may watch the weather maps for knowledge of the 

 broader changes to come, and may observe the sky for indica- 

 tions of local changes nearer at hand; and in both may profit 

 by the study of the atmosphere. 



