AEROGRAPHER'S MATE 3 & 2 



60 



40 



20 



- 



20 



40 







kg* 



1 E 0R 



TH TEMPER 



* 



1 t 



POLAR ZONE 







^** 





m 



I0R 



i3 



ATE 2 



ONE 



lllll 



























-«■■ 



^HOT BEL" 



r *M! 









y> 











JTO 













™**n 













ISh 







































1 



is 



OUTH 



c 



1 



TEMP 



ERAT 



e zof^ 



IE 































UUIH 



1 



POL) 



1 ' 



\R ZO 



Nb 



50°F ISOTHERM 

 (Wormest Month) 



MEAN ANNUAL 

 ISOTHERM OF 68°F 



MEAN ANNUAL 

 ISOTHERM OF 68°F 



50°F ISOTHERM 

 ( Wormest Month) 



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



Figure 13-7. — Temperature zones. 



210.2 



the distance from the Equator. (See fig. 13-8.) 

 Therefore, the extent to which an air mass is 

 heated is influenced by the latitude. 



Influence on Air Temperature. — Regions 

 under direct or nearly direct rays of the sun 

 receive more heat (per unit of time) than those 

 under oblique rays. The heat brought about by 

 the slanting rays of early morning may be 

 compared with the heat that is caused by the 

 slanting rays of winter. The heat which is due 

 to the more nearly direct rays of m'dday may 

 be compared with the heat resulting from the 

 more nearly direct rays of summer. 



The length of the day, like the angle of 

 the sun's rays, influences the temperature. The 

 length of the day varies with the latitude and 

 the season of the year. 



The hot and humid climates of equatorial 

 Africa and South America are good examples 



of the influence that latitude has on climate. 

 At no time during the year are the sun's rays at 

 much of an oblique angle. Therefore, there is 

 little difference between the mean temperatures 

 for the coldest and warmest month. Contrast 

 this picture with the opposite extreme, such 

 as in the far north, where the sun is below 

 the horizon for a great deal of the time during 

 the winter, producing cold temperatures that 

 breed powerful polar outbreaks. During the long 

 hours of summer daylight the sun's rays make 

 such a small angle with the earth's surface that 

 the energy received per unit area is extremely 

 small and the sun's effectiveness is minimized 

 even though it may shine for days without 

 ceasing. It is, however, sufficient to thaw lakes 

 and weaken the polar air masses. 



LAND AND WATER DISTRIBUTION. — Be- 

 cause land and water heat and cool at different 



300 



