青藏高原和四川盆地夏季对流性降水特征的对比分析

本文利用TRMM(Tropical Rainfall Measure Mission)多种探测结果,针对青藏高原和四川盆地各两次对流性降水天气进行了对比分析,结果表明:(1)高原降水系统以对流云降水为主,弱降水样本数量高,由孤立零散的块状降水云团组成,对流中心离散,降水范围小,雨区极不均匀,垂直发展厚度浅薄,降水粒子数量少,雨滴小,潜热释放以地面以上2~5 km高度层为主,夏季近地面层冰晶粒子含量高,降水过程中云顶亮温与地表雨强之间的相关性差,云顶亮温越高的对流云团其闪电频数越高。(2)盆地降水系统强降水样本数量高,由一个主降水系统和周边零散的降水云团组成,降水范围大,对流中心相对集中,雨区较均匀,垂直发展厚度高,对流系统深厚,雨滴大并集中,潜热释放呈一致的双峰型结构,峰值分别出现在7和16km高度上,冰雹粒子在对流层较高层含量高,云顶亮温与地表雨强之间呈显著的负相关,盆地的闪电频数显著高于高原地区,且闪电活动主要集中在亮温偏低的降水云体中。

Comparative Analysis on Characteristics of Summer Convective Precipitation over Tibetan Plateau and Sichuan Basin

The convective precipitation events that respectively occurred in Tibetan Plateau (TP) and Sichuan Basin are compared and analyzed by using TRMM (Tropical Rainfall Measure Mission) data. The results show that the precipitation system in the TP is mainly convective cloud precipitation and weak rainfall samples are a great many consisting of isolated cloud precipitation cloud clusters. Convective center is scattered, with small precipitation range, uneven rain belt, shallow vertical thickness, fewer precipitation particles and small raindrops. The latent heat which is released at the height of 2-5 km is dominant. The content of ice crystal particles near the ground layer in summer is great. There is a poor correlation between brightness temperature of cloud top and rainfall intensity near surface. The higher the brightness temperature, the larger the number of lightning frequency. In contrast, the precipitation system in Sichuan Basin has more severe precipitation samples, consisting of a main precipitation system and scattered cloud clusters. Convective centers are concentrated, the precipitation scopes are large, rain belt is even, vertical thickness is deep, and raindrops are large. The latent heat is released in the pattern of two peakes and the peak values appear at the heights of 7 km and 16 km. The content of hail particles are much more in the upper level. There is a negative correlation between brightness temperature of cloud top and rainfall intensity near surface. The number of lightning frequency in Sichuan Basin is heigher than the TP areas, and lightnings mainly appear in the clouds with lower bightness temperature.