辽宁地区一次暴雨过程成因的位涡诊断分析

2003年8月5—6日，受东移北上的华北气旋的影响，辽宁省大部分地区出现暴雨天气，其中彰武、本溪等地出现局地大暴雨。应用MM5非静力中尺度模式对这次暴雨过程进行了数值模拟，在模拟结果的基础上，利用位涡分析方法对这次过程进行了诊断分析。结果表明，在对流层低层有正位涡扰动存在，对强对流天气具有触发作用；对流层中低层的相对高位涡中心和对流层高层的较强低位涡中心相配合，有利于形成低层辐合与高层辐散，使得气旋得以维持和发展，从而为对流性降水提供了必要条件；在对流层中低层，出现高位涡中心地区可能形成暴雨中心。

Diagnostic analysis of potential vorticity for cause of a rainstorm in Liaoning area

By using MM5 model, a rainstorm in Liaoning Province caused by the North China cyclone during August 5 - 6, 2003 was successfully simulated . The rainstorm course was analyzed by using the theory of potential vorticity. The results show that the positive potential vorticity disturbance in lower-troposphere play a trigger role in severe convection weather; A relatively high potential vorticity center in low-troposphere make cyclone develop in a more deep cyclone circulation, and an anticyclone circulation zone with more severe low potential vorticity in high-troposphere make anticyclone circulation. Low-level cyclone circulation with high-level anticyclone circulation, is favorable to form low-level convergence and high-level divergence, and make the rising airflow nearby cyclone maintain and strengthen so that it can offer necessary condition for convection precipitation; The area of the high potential vorticity center in low-troposphere is formed into rainstorm center probably.