一次局地强降水过程的中尺度特征及预报难点分析

The Forecasting Difficulties and Mesoscale Characteristics of a Local Heavy Precipitation

利用常规气象资料和客观物理量场、卫星云图、多普勒雷达回波产品资料,对2007年8月30日发生在宜昌市北部的强降水天气过程的中尺度特征和预报难点进行了分析。结果表明:(1)地面中尺度辐合线、中尺度对流云团是造成此次强降水的重要中尺度系统;(2)强降水主要由一中尺度"人"字型雷达回波带稳定少动造成,回波带中有强对流单体不断新生、合并使强降水得以维持;(3)回波带上出现的逆风区与强降水落区有较好的对应关系,风切变区面积扩大和切变值增大是强对流回波单体不断发展并在一地维持的主要原因;(4)中低层偏南风到高层偏北风的转变所形成的垂直风切变为强降水的发生提供了动力条件,同时中低层暖湿平流加强为强对流云团的稳定维持提供了充足的水汽;(5)强对流单体,强回波短带,速度资料上的"逆风区"和风切变区等,可作为判断强降水落区的依据。

Based on the conventional observations,satellite cloud images and Doppler radar data. the mesoscale features and forecast keys of a heavy precipitation process occurring over north of Yichang on 30 August 2007 is analyzed. （1）Surface meso-scale convergence line and meso-scale convective cloud cluster are the main mesoeale systems causing the heavy precipitation. （2） The heavy rain is caused by a stability mesoseale vortex zone fixed in the northern part of Yichang with new convective cells and their merging. （3） Upwind area in the echo is coincident with the precipitation center. The extended areas and the enhancement value of the Wind shear caused the echo intensified stability. （4） The vertical shears are the main dynamic factors for the heavy precipitation, the warm and moist air advection in boundary layer provides the abundance vapor. （5） The convective cells, strong echo zone, upwind areas and Shears can be used to judge the rainstorm areas.