Chapter 14 — AIR MASSES AND FRONTS 



COOL CONTINENT 



WARM OCEAN 



Figure 14-4. — When cP air of winter moves from cool continent to warm ocean. 



210.76 



unstable air mass. The convective activity is 

 increased as the air mass is lifted over the 

 mountain ranges along the western coast of 

 the continent. This lifting results in heavy rain 

 and snow showers with considerable turbulence 

 and icing on the windward side of the mountains. 

 (See fig. 14-5.) If the trajectory of the air 

 mass as it moves across the ocean is cyclonic, 

 the instability is increased; if it is anticyclonic, 



the instability is decreased. Maritime polar air 

 may acquire stable characteristics in its lower 

 levels before reaching the continent if it moves 

 over cold ocean currents after its original 

 modification. When this occurs, it is charac- 

 terized by stratified clouds, fog, and drizzle. 

 Maritime polar air of Atlantic origin which 

 occasionally affects the eastern coast of North 

 America differs in two respects from that of 



mPk » 



CLEAR COLO 



-20°C 



f 



-20°C w^f*^ 



TURBULENCE r fff'9^C ,n *?l 



14 4 HEAT AND MOISTURE 

 _i_i R ' SING 



ALEUTIAN "**Xyy ^ PACIFIC OCEAN ^ rfg* SHOWERS » *• S 



: ISLANDS :j£ o°C WATER TEMP 10° C 

 mmtrfm—m—mllll m ■ — m^^mrrrmmm 



NW. . 



20°C 



SE 



Figure 14-5. — Movement of mPk air southeastward. 



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