西南地区东部一次大暴雨的中尺度数值模拟

Mesoscale numerical simulation of heavy rain in east of southwest China

利用中尺度数值模式MM5V3.5对2007年5月23—25日发生在贵州的一次大暴雨过程进行48 h的数值模拟研究,并结合天气形势、雷达回波和卫星云图演变对此次过程进行分析。结果表明:模式较成功地模拟了这次强降水过程,模拟出了暴雨的强度、位置以及随时间的变化。导致这次大暴雨发生的主要影响系统是中尺度低涡,它的稳定维持是暴雨产生的主要原因。中尺度系统的发展、增强、减弱,主要由低层的正涡度产生。高层辐散、低层辐合、强烈的垂直上升运动是大暴雨天气维持和发展的可能机制之一,强降水与强烈的上升运动区和正涡度区有很好的对应关系。

Using the mesoscale numerical model MM5V3.5, a heavy rainfall process happened in Guizhou province on 23--25 May is numerically simulated for 48 h and the analyses are made by the synoptic character, radar echoes and evolution of satellite images of the process. It is shown that the MM5 model can successfully simulate the heavy rainfall process, strength, position and time variation of heavy rain. The main effective system inducing the heavy rain is the long-lasting mesoscale low vortex. The development, intensification and weakening of mesoscale systems mainly are caused by positive vortex at lower layer. The low-level atmospheric convergence and the upper-level atmospheric divergence, the strong vertical motion are one of the possible mechanisms of maintaining and development of the heavy rainfall, the heavy rain field has a good relation to the strong ascending motion and the positive vortex.