“07.7”重庆暴雨的数值模拟分析

The Numerical Simulation and Analysis of "07.7" Heavy Rainfall of Chongqing

针对2007年7月17日发生在重庆地区的一次暴雨过程,利用AREM模式进行了数值模拟。结果显示,AREM模式较好地模拟了这次暴雨过程的雨带及雨带上双极值中心的分布。利用模式输出的高时空分辨率结果,对暴雨过程的中尺度特征进行了诊断分析,得到的主要结论有:24h累积降水的双中心峰值发生在不同时段;暴雨中心的动力场结构随时间的演变与降水量在中尺度特征值上有很好的对应关系,两个降水中心对应高低层的流场配置不同;暴雨是在西南涡及低空西南急流的直接作用下发生发展,低涡和急流的维持为降水中心的低层辐合及与之伴随的上升气流的发展提供了有利条件;对流层高层高压脊的变化和中尺度辐散区发展也是造成此次降水的重要因素,辐散区的移动造成强上升运动区的移动,这是引起降水中心移动的原因之一。

The heavy rain of Chongqing on 17th July, 2007 is studied through the numerical simulation in AREM. The results show that the distribution of rain belt, the existence of two heavy rain cells and the synoptic situation field were well simulated. The diagnosis of model output with high spatial-temporal resolution is used to study the meso-scale characteristics of this heavy rain case. It is concluded that the accumulated 24h precipitation of two rain cells peaks occurred at different time. The meso-scale characteristic of evolution of dynamical structure in rain centers is consistent with that of the precipitation, and the vertical allocation of the stream in one center is different from that in another center. The heavy rainfall is directly affected by the low southwest vortex and low -level jet. As the vortex and jet stream at low levels strengthen the low level convergence and its attendant ascending motions, the heavy precipitation maintains its intensity. Both of the development of the ridge and meso-scale divergence field on upper troposphere are also the important factors leading to this rainfall, and the transfer of divergence field that leads to a movement of strong ascending region accounts for one of cause to transfer the rainfall center.