CLIMATOLOGY 



bined with the high surface winds produces the typical 

 Antarctic bHzzard. 



Hence Simpson follows Meinardus as regards the 

 method of precipitation from an upper cyclone. But 

 he raises the "snow-supplying cyclone" more than three 

 thousand meters above the plateau so that it does not 

 show in the figure. He thinks that the plateau itself 

 is everywhere controlled by a shallow surface anti- 

 cyclone, but his map omits this as its position is in- 

 definite. 



Some attention may now be given to these Antarctic 

 pressure waves on which Simpson lays great stress. 

 It is found that local variations in pressure in this 

 region are usually not accompanied by changes of wind 

 direction, as in lower latitudes. A series of these 

 waves moves across the Ross Sea area, first afifecting 

 the Southern Plateau and Framheim (see Figure 30), 

 and then moving to the northwest and reaching Ross 

 Island and lastly Cape Adare. The mean length (time 

 of passage) of such a barometric wave is one hundred 

 and fifty hours, and the mean variation amounts to 

 0.572 inch. These waves apparently have a velocity 

 of about forty miles an hour. They seem to affect 

 much of Antarctica, but have not been detected in 

 New Zealand. 



The usual pressure conditions near Ross Island con- 

 sist of a more or less permanent low over the warm 

 Ross Sea, and a permanent high over the cold Plateau. 

 Thus the normal winds would be southerly or south- 

 east winds. Simpson believes that the pressure waves 



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