汉江流域一次致洪暴雨过程的诊断分析

DIAGNOSTIC ANALYSIS OF A FLOOD-CAUSING HEAVY RAINSTORM OVER HANJIANG RIVER BASIN

应用常规气象观测资料和NCEP格点资料.对2005年出现在汉江上游和渭河流域秋季连阴雨中一次致洪暴雨过程进行诊断分析,结果表明:这次过程的主要影响系统是西风槽、低涡切变和副高。水汽条件中,700 hPa水汽通量大值中心和其散度的辐合中心与暴雨落区基本重叠.强降水出现在高层峰值与低层谷值之间的时段内,说明比湿高层峰值和低层谷值的出现对暴雨的开始和结束有重要的预报意义。θ_(se)分析表明:致洪暴雨出现在550 hPa以下能量锋区中.与陕西秋季暴雨一般出现在低层稳定层结中有一定区别。强降水时段内,高层幅散、中低层强辐合,使垂直上升运动发展强烈至对流层顶,这是本次致洪暴雨动力场结构的主要特征。

The routine meteorological data and NCEP grid data are used to diagnostically analyze a flood-causing heavy rainstorm happened in autumn in 2005. The result shows that the main influence system is west -wind trough,low-level shear and subtropical anticyclone. As for the vapor condition, 700 hPa wet center and moisture convergence coincide with the area of rainstorm. Since heavy rainstorm appears at the time interval between occurrence of high level peak value and the low level minimum value of specific humidity,the latter appearance can be used to predict the start or end of rainstorm. Analysis of θse shows that the flood-causing heavy rainstorm happened at energy frontal zone under 550 hPa, and differs from rainstorm happened in autumn in Shanxi. During the heavy rainstorm, divergence at high level and great convergence at mid and low level cause strong rising movement to develop to the top of troposphere, and this is the main feature of dynamic structure of the heavy rainstorm.