淮河流域暴雨过程模拟分析

Numerical Simulation of a Heavy Rainfall Event over Huaihe Valley

以2003年7月3～4日发生在淮河流域特别是安徽省北部的强降水过程为例，利用全物理过程的中尺度气象模式MM5对此次暴雨过程进行数值模拟，通过对暴雨过程中、低层的环境背景、降水量、降水生命期和降水总体分布随时间演变的趋势以及中尺度对流系统的雷达回波特征等方面的检验，发现MM5模式对此次大暴雨过程具有一定的模拟能力，模式基本可以模拟出中α尺度和100km左右的中β尺度天气系统，但对于时空尺度更小的且发展比较强盛的中β（γ）尺度系统，则有较大的局限性。利用高分辨率模式输出结果验证了低层中β尺度辐合线是造成此次大暴雨的中尺度影响系统，并通过对物理量场特征的分析得到该辐合线的三维结构特征。

Numerical simulation is made on the heavy rainfall over the Huaihe valley on 3 to 4 July 2003 using the PSU/NCAR MM5 model. It is revealed that the MM5 model performed quite well in simulating and can provide high-resolution data for diagnosis. The meso-α-scale and meso-β-scale convective systems of about 100 km can be simulated out by the MM5 model, but the model has a limited capability in simulating the meso-β（γ）-scale systems of smaller scales or more strongly developed systems. The direct reason of the heavy rainfall event is the rapid development of the about 100 km long meso-β-scale convergence zone at the lower levels, which is validated by the high-resolution data provided by the MM5 model. The mechanisms and the 3D structure of the mesoscale convergence zone are obtained by the diagnostic analysis of the physical quantity field characteristics.