deck of the mAw section frequently disappears. Maritime ant- 

 arctic air flowing parallel to the continent becomes mAw upon 

 passing over the ice pack. This change, after a distance of about 

 200 miles, produces dense fog which blankets the ice pack area 

 and is frequently advected over the sea. If the fog advected over 

 the sea has a northward trajectory, the air will be warmed from 

 below and the fog will lift and form a stratus cloud deck after a 

 distance of about 3 to 5 miles. 



"The mP air mass that lies to the northward of the Antarctic 

 Front is homogeneous in its east-west characteristics with a rapid 

 north-south variation in temperature which closely corresponds 

 to the sea surface temperature. The lapse rate is moist adiabatic 

 to 10,000 to 15,000 feet where a small stable layer tops this moist 

 layer. In convergence zones or where the air has an mPk classi- 

 fication, heavy cumulus clouds develop in the moist layer giving 

 snow showers. These cumulus clouds frequently resemble cum- 

 ulo-nimbus with flattening of tops, but on a reduced scale. They 

 appear to be composed of super-cooled water drops through their 

 major portion, with an ice crystal top. 



"Patchy fog develops where the air becomes mPw provided 

 there is no extremely large scale meridional flow such as is present 

 in advance of a large low pressure area. In this latter case, the 

 fog becomes solid advection fog and persists as long as that 

 meridional flow exists." 



WINDS 



From the antarctic continent outward blowing winds prevail, 

 and since the coast so generally trends east-west, these winds, 

 which are always deviated to the left by the earth's rotation, gen- 

 erally blow from the southeasterly quadrant. Where, however, 

 the coast trends north-south, as on the west of the Ross Sea, these 

 winds for the same reason blow from the southwest. They are 

 often of hurricane intensity and with gust velocities sometimes 

 attaining to 150 or 200 miles per hour. Winds of such violence 

 are not known elsewhere, save perhaps within a tropical cyclone. 

 They are characterized by a noteworthy absence of humidity and 

 an elevation of air temperature due to the adiabatic conditions. 



The Antarctic Anticyclone, being due to the intense cold of the 

 snow surface, is essentially a shallow system not more than some 

 few thousand feet deep, and above it the general polar cyclone 

 must exist in an intensified form. The upper winds are best 

 shown by the movements of the clouds and by the drift of the 



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