贵州一次大暴雨过程的中尺度数值模拟与诊断分析

Mesoscale Numerical Simulation and Diagnostic Analysis of a Heavy Rainfall in Guizhou

利用三重嵌套的非静力中尺度数值模式MM5V3.5,对2005年5月31日至6月1日贵州省发生的一次大暴雨天气过程进行数值模拟,并利用模拟结果对该过程进行诊断分析。结果表明:模式较好地模拟这次大暴雨过程,并对与暴雨过程相关的中尺度系统的发生发展做出了较成功的模拟,此次过程中,西南涡是造成大暴雨的主要影响系统。对中尺度系统的模拟表明:强降水与强上升运动区及正涡度区有很好的对应关系,低层辐合、高层辐散、西南低空急流、垂直运动增强等是此次暴雨维持和发展的重要机制之一。强降水与水汽辐合的大值密切相关,降水的强弱与辐合的强弱变化一致。

Using the three-way nested nonhydrostatic meso-scale numerical model MM5V3.5, the heavy rainfall process happened in Guizhou province on May 31 to June 1 is numerical simulated, and the diagnostic analyses are made by the output results of the model. It is shown that the MM5 model can successfully simulate the heavy rainfall and the development of the meso-scale system which related to the heavy rainfall, the southwest vortex is the basic cause of the event. The simulation result shows that the heavy rainfall field is homologous with the positions of both the strong ascending motion and the positive vorticity, the low-level atmospheric convergence and the high-level atmosphere divergence, the southwest low level jet, the strong vertical motion are the possible mechanisms for maintaining and growing of the heavy rainfall. The heavy rainfall is closely associated with the maximum of the moisture convergence, and the intensity of the rainfall accords with the intensity of moisture convergence.