基于TRMM卫星探测对宜宾夏季两次暴雨过程的比较分析

Comparative analysis between two summer heavy rain events in Yibin based on the TRMM data.Acta Meteorologica Sinica

利用TRMM卫星和宜宾多普勒雷达探测结果,比较分析了2007年夏季在宜宾发生的"2007.07.09"和"2007.08.23—25"两次区域性暴雨过程降水云团的水平和垂直结构变化特征、降水云团风廓线变化特征,结果表明:(1)这两次暴雨过程降水水平结构均为中尺度对流降水系统,但"2007.07.09"暴雨过程比"2007.08.23—25"的降水强度和范围要大得多,且垂直结构表现为强对流性降水云团的云顶高度分别达17、14 km;(2)两次过程的层云降水率廓线差异并不大,随高度增加,降水强度呈减小趋势,而它们的对流降水率廓线差异较大,降水增长区分别由碰并层向冰水混合层转移和由冰水混合层向碰并层转移的趋势;(3)雷达风廓线上,发现"2007.07.09"大暴雨区存在低层辐合高层辐散的典型垂直环流结构,减弱时降水云团的高度有所下降,且在垂直方向上降水云团活动均为连续的,而发现"2007.08.23—25"东风波过来时有冷暖平流的一个变化情况,且降水云团活动是时断时续的。

Using the observational data from the TRMM satellite and Doppler radar at Yibin,the Vertical Wind Profile（VWP） change characteristics,rainfall structure characteristics and rainfall profiles for the two regional heavy rain events in Yibin in 2007 are analyzed in this paper.The results show that;（1） The two precipitations are all caused by mesoscale systems as indicated by their respective horizontal rainfall pattern,and although the rainfall intensity and scope of the event occurred in July are much larger than those of the event in August,their vertical structure implies a severe convective cloud cluster developed therein with its cloud top height up to 17,14 km;（2） the difference between the two profiles of stratus precipitation rate is not distinct with the trend of precipitation intensity was reduced with increasing height,while their convective precipitation rate profiles are quite different from each other with the shifting direction of precipitation growth areas being just opposite：for the former event the area is shifted from coagulation layer to mixed layer and for the latter it is from mixed layer to coagulation layer; （3） the typical vertical circulation structure of convergence in lower levels and divergence in upper levels is found over the heavy/torrential rain areas in the＂July-event＂based on the VWP data with the precipitation cloud clusters moving continuously, but there exists no such a typical structure with the＂Angust event＂in which the alternative warm or cold advection occurs in the case of easterly waves coming and the activity of rainfall is discontinuous.