“96·8”华北暴雨数值模拟与稳定性分析

分析1996年8月发生在华北地区的台风暴雨过程的环流形势，发现：副热带高压与台风低压之间的气压梯度很大，宽广的偏南急流源源不断地向北输送水汽和能量，而太行山一带正处于汇合区，构成十分有利的暴雨天气形势。应用MM5数值预报方法对1996年8月4—5日的降雨天气过程进行数值模拟，并依据天气学原理和位涡理论对此过程的稳定性进行分析认为：（1）MM5数值预报模式较好地模拟出了台风暴雨的物理过程。（2）此次降雨的不稳定层结有南高北低现象，同时有对称不稳定和对流不稳定存在；条件性对称不稳定可使环流加速，对降水有一定的增幅作用。

Numerical Simulation for "96.8" Huabei Heavy Rain and Its Stability Analysis

The circulation patterns of the heavy rain process in Huabei area on August 1996 was analyzed. The results show that the gradient between the subtropic high and typhoon is so strong that broad southerly jet continuously transports the water vapor and the energy to the north. The Mount Taihang was just located in convergence area, so it formed the advantageous weather situation for rainstorm. Based on MM5 numerical model, in term of the synoptic principle and the potential vorticity theory, the rain process of 4-5,August 1996 was simulated and its stability was analyzed. The main results are as follows: (1) MM5 model has a good performance to simulate the typhoon rainstorm physical process. (2)In this rain process, the instability stratification in South is higher than that in North, and there are symmetry instability and convection instability simultaneously. In addition, the conditional symmetric instability not only causes the circulation acceleration, but also increases the precipitation.