一次江淮大暴雨过程中尺度系统结构分析

本文应用观测资料和中尺度数值模拟结果对1999年6月23日发生在江淮地区一次梅雨锋暴雨过程进行研究，揭示了影响这次暴雨过程的物理条件、云团的演变特征及与中尺度系统的关系，分析表明，在暴雨生成和发展过程中，多个中尺度云团在相继生成和移动发展，暴雨中心是几个发展较强的中尺度对流云团造成的，西南风低空急流为暴雨提供了水汽输送，并且通过强垂直运动向对流层中上层输送水汽，这次暴雨与中尺度系统发生发展有直接关系，西南涡分裂出一系列的小涡旋，这些小涡旋边向东移边减弱，并且同时在地面上引发小低压，这些中尺度低压增强低空水平辐合，成为触发不稳定能量的机制，低空急流中心与雨区相互对应，且急流风速增强，风速水平切变梯度增大的过程对应着强降水过程。

ANALYSIS OF MESOSCALE SYSTEM STRUCTURE ON THE TORRENTIAL RAIN OVER THE YANGTZE RIVER

Using the observational data and numerical simulation results ,the physical condition and evolution of cloud clusters and the relations between mesoscale systems that caused the storm rainfall on Mei yu front over the Yangtze River are studied in this paper.Analysis shows that several mesoscale cloud clusters that develop severely caused the rainfall in precipitation cell.Southwest low level jet provides water vapour for the rainfall,and the transportation of the water vapour to the upper air is done by the vertical convection.This rain related the appearance and development of mesoscale system directly,southwest vortexes separates many little vortexes that move to east and weaken gradually.These little vortexes bring little low pressure system on surface which enlarges the horizontal divergence of lower air and becomes the mechanism of triggering the unstable enery.The center of low level jet is consistent with that of rain,the wind velocity strength of jet and the enlargement of horizontal velocity shear gradient is consistent with the process of torrential rain.