AEROGRAPHER'S MATE 3 & 2 



day, with frequent thunderstorms by late 

 afternoon., (See fig. 14-8.) Flying conditions 

 are not hazardous despite the thunderstorms 

 because they are easily circumnavigated. Ground 

 fogs are frequent with northward movement of 

 mT air over land. Sea fogs are frequent with 

 movement over water. The famous fogs of the 

 Grand Banks are typical of mT air over a 

 cold ocean current. 



When mT air invades southwestern Europe, 

 the weather is somewhat cooler than in the 

 United States because of the cold ocean currents 

 and the stable anticyclonic circulation. Over 

 water, mT has stratiform low clouds, fog, and 

 drizzle. Over land the air is subject to con- 

 vection. 



Asian mT air originating over the Pacific 

 is usually observed along the coast of China 

 and over the islands of Japan; it is extremely 

 warm, moist, and unstable. Weather conditions 

 encountered in it are similar to its North 

 American counterpart. In summer this air is 

 replaced in southeast Asia with equatorial air, 

 and it is this equatorial air which brings with 

 it the monsoon of that region. Over the western 

 North Pacific great fog banks form in summer 

 in mT air, much in the same manner and for 

 the same reason as do the fog banks over the 

 Grand Banks of the Atlantic coast. 



CONTINENTAL TROPICAL. — Tiis air is 

 found only during summer, forming over a 

 small area of northern Mexico, western Texas, 

 New Mexico, and eastern Arizona. It can be 

 identified by its extremely high surface tem- 

 peratures, very low humidities, large diurnal 

 temperature ranges, and rare precipitation. 

 Flying conditions are excellent with respect 

 to weather, but clear air turbulence is 

 extensive. 



European cT air masses have their source 

 regions in north Africa and Asia Minor, As 

 they move into southern Europe, much moisture 

 is added and instability showers result. In 

 north Africa and Asia Minor, cT air is present 

 all year round. During summer, the north 

 African air mass is the hottest air mass on 

 record in the world. It is extremely warm 

 and dry, but quite unstable. 



In the Southern Hemisphere, cT air is found 

 in summer in South America, Australia, and a 

 small area of south Africa (the Kalahari 

 Desert), The South American cT air is usually 

 modified mT air. The south African cT air 

 mass is small and somewhat cooler than either 

 of the other Southern Hemisphere cT air 

 masses, Tne Australian cT air is similar in 

 all characteristics to the north African cT 

 air mass. 



The mT air masses of the Southern Hemi- 

 sphere are quite similar to their counterparts 

 of the Northern Hemisphere; that is, on the 

 east coast of South America, South Africa, and 

 Australia, the weather is similar to that on 

 the east coast of North America. On the west 

 coast of South America, Australia, and south 

 Africa, the weather is similar to that on the 

 North American west coast. 



EQUATORIAL AIR. — Equatorial air is the 

 air on either side of the thermal Equator, 

 with the Intertropical convergence zone (ITCZ) 

 separating the Northern and Southern Hemisphere 

 equatorial air. It is warmer than mT air, and 

 more moist at all levels. In India and southeast 

 Asia this air is often referred to as monsoon 

 air. During summer it is characterized by 

 extreme convective activity and heavy showers 

 in both hemispheres. 



WARM OCEAN 



WARMER CONTINENT 



SUPERIOR. — As v/as pointed out previously, 

 S air is observed in the Northern Hemisphere 

 both in winter and in summer. The only 

 difference between winter and summer S air 

 is that the temperatures are higher in summer. 



PROPERTIES 



209.370 

 Figure 14-8. — mT (Gulf or Atlantic) air of 

 summer moving northward over warm continent. 



In studying air masses, it has been deter- 

 mined that the physical properties of an air 

 mass depend upon its life history. 



322 



