91年夏一次梅雨锋暴雨过程数值模拟结果有关结构的诊断研究

A DIAGNOSTIC SURVEY OF NUMERICAL SIMULATION ON A MEIYU FRONTAL RAIN STORM IN THE SUMMER OF 1991

本文利用MM4模式对91年6月30日～7月2日暴南天气过程进行了数值模拟，并对模拟结果进行了诊断分析，着重研究了高低空急流对强降水的影响．发现当降水区位于高空急流人口区的南侧和低空急流出口区的北侧时，极易产生强对流而出现暴雨，而这种相对位置的配置则与高空急流分裂为南北两支有关。低层温度场的演变进一步证实了，来自准静止锋后部的小股冷空气沿锋面东移为暴雨的维持起着重要作用。最后给出了模式输出的沿静止锋温度场、散度场和湿度场等的分布特征。

In this paper a numerical simulation was carried out for a heavy rain process occurring along the Yangtze river from 30 June to 2 July' 1991, using the PSU/NCAR meso-scale model (MM4), and then the model output data was used for diagnostic analyses. Analyses confirmed that when the precipitation area was located to the south of the entrance region of the upper tropo-spheric jet and the north of the exit region of the lower jet, the favorable conditions of the development of severe convection and heavy rain were usually formed. The appearance of this type of relative positions fo upper and lower jet frequently associated with the upper jet splitting in which both south-and north-jets were setout. The evolution of lower layer temperature fields further verifies that the cold air coming from the rear of the quasistationay front acts an important role in the maintain of heavy rain. At the end, the features of vorticity divergence and humidity fields along the front was depicted