Summer precipitation onto the South Polar Plateau

概要

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A study was made of ice crystal precipitation in austral summer 1978-1979 at the South Pole from analyses of data of meteorological observations, in which low-level micrometeorological elements were measured by conventional apparatus and high-altitude elements were measured by radiosondes. The result shows that ice crystal precipitation can be classified into "clear sky precipitation" and precipitation from clouds. The latter plays a dominant role in net accumulation of snow at and near the South Pole. In this case moist air masses move inland in advective flow along the surface of Antarctica from the Weddell and Ross Seas and cool down to form stratus-type clouds from which ice crystals fall at the South Pole. The former, on the other hand, presents an interesting phenomenon, as ice crystal precipitation falls from a clear sky. This study has disclosed that it originates in a layer which is supersaturated with respect to ice, located slightly above the ground surface, and too thin to be identified as a stratus cloud. It will be sufficient to consider that the former represents a short-life transition from the absence of precipitation from a clear sky to precipitation from clouds and v.v.; hence, it cannot play an important role in net accumulation of snow there.