摘要
本文根据二维基本气流的理论,通过实例分析了梅雨锋附近的条件性对称稳定度的分布和演变;它与准地转锋生环流的相互作用;它与锋区垂直结构及大尺度水平环流的关系。发现对流不稳定大气因垂直对流而达到对流中性后,可能由于局地条件性对称不稳定而激发斜对流;如果暖区条件性对称稳定度很弱,准地转锋生环流的上升支也会产生类似对流的强降水带,从而使暴雨在对流稳定的条件下持续。这种条件性对称不稳定和弱稳定性与锋区的垂直结构、大范围水平环流、尤其与200hPa南亚高压及500hPa西太平洋副高脊线的相对位置有关。
In this paper, the distribution of conditional symmetric stability over and around the Mei-Yu front is analysed in real case studies based on the theory of 2-dimensional flow. The effects of this kind of stability on the quasi-geostrophic frontogenetic vertical circulation and its connections with the vertical structure of the front as well as the large scale horizontal circulation patterns are also examined. The results suggest that slantwise convection may occur due to local conditional symmetric instability after the initially convectively unstable layer is stabilized through vertical convections. Under the condition of small conditional symmetric stability in the warm and moist air, the ascending branch of the frontogenetic circulation can be intensified to produce a rainbelt similar to convections. Therefore, conditional symmetric instability and weak stability could maintain the heavy rainfall observed along the Mei-Yu front. Their occurrence is related to the vertical structure of the frontal region and the horizontal circulation in the mid-and-upper troposp-nere, especially the south Asia anticyclone at 200hPa and the west Pacific subtropical high at 500hPa.
出处
《热带气象》
CSCD
1990年第2期180-187,共8页
基金
国家自然科学基金
国家气象局季风科研基金
