1991年1月奄美大島における下層雲と境界層の観測結果について(第2報)

Abstract

比較的暖かい海上への寒気の吹き出しによる対流混合層と下層雲を1991年1月に奄美大島より観測した。寒気の吹き出しに伴い海面から大気への熱フラックスが増加して対流混合層が発達し, また雲底高度が上昇し下層雲量が減少した。雲底下の境界層において比較的一様な鉛直流である場合には雲量が多く層状の雲になり, 上昇・下降流域がよりはっきりと分かれている場合では雲量が少なく積雲状となるという傾向が観測された。

The convective mixed layer and low-level clouds developed by cold-air outbreak over warmer ocean were observed at Amami-ohshima Island in January 1991.After the cold-air outbreak, heat flux from the sea surface to the atmosphere became large and the mixed layer developed. Moreover, the height of cloud base increased and the low-level doud cover became small. The observation indicated the following general tendency. In case of relatively homogeneous vertical air motion in the sub-cloud boundary layer, the cloud cover is large and its appearance is stratiform. On the other hand, in case of distinct spacial seperation of upward and downward vertical air motion, the cloud cover is small and its appearance is cumuliform.