APPENDIX A 



ANTARCTIC CLIMATE AND WEATHER 



The antarctic continent consists of a large elevated land mass 

 which is almost entirely covered by ice. This condition leads to 

 formation of the permanent Antarctic Anticyclone (high pressure 

 area) with the center located near the South Pole. This anti- 

 cyclone is modified only by the semipermanent cyclones (low pres- 

 sure areas) located in the Ross, Weddell, and Bellingshausen Seas. 

 To the north of the Antarctic Circle is a belt of low pressure cir- 

 cling the globe which, in general, conforms to the northernmost 

 edge of the off lying pack ice. Cyclonic storms moving from west 

 to east in this low pressure belt tend to move directly into the 

 semi-permanent cyclonic regions mentioned above, reenforcing 

 the cyclonic circulation of these areas and losing their identity 

 in doing so. (Refer to H.O Chart No. 2562 for the geographical 

 features of Antarctica.) 



A region of high pressure, as already mentioned, lies over the 

 high Antarctic continent. The upper air descends over the polar 

 ice cap, becomes intensely cooled, and moves outward in anticy- 

 clonic circulation toward the bordering belt of low pressure over 

 the oceans surrounding the continent. In flowing downward from 

 the polar plateau, these winds become southeasterly, due to the 

 earth's rotation. They usually attain hurricane intensity, and 

 blow drift snow high up in the air. Millions of tons of snow at 

 low temperatures are at such times carried into the sea and play 

 a large part in the regime of sea ice of the southern hemisphere. 



Obstacles, such as the high mountains of South Victoria Land 

 and Palmer Peninsula, produce a concentration of moving air, 

 resulting in the high winds recorded in the McMurdo Sound and 

 Marguerite Bay areas. Local winds of great intensity, some of 

 which may be a reversal of the prevailing continental winds, are 

 found in local areas, particularly where the terrain is marked by 

 glacier valleys transverse to the flow of the prevailing air currents. 

 Local disturbances may be confined to a relatively small area, with 

 calm weather existing only a few miles from the area of high 

 winds. 



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