一次特大暴雨过程的数值模拟试验

利用MM5V3非静力模式对2003年8月25日12：00至26日00：00发生于鲁西南地区的一次特大暴雨天气过程进行了数值模拟分析.模式较成功地模拟了这次特大暴雨天气过程,再现了中β尺度低涡的发生、发展和消亡过程.数值模拟结果表明：本次暴雨过程具有较强的中尺度特征,暴雨区上空低层近东西向的切变线及其强烈的辐合上升运动和高空急流核人口处右侧的辐散上升运动的耦合,是导致中β尺度低涡迅速发展而产生此次特大暴雨的触发机制,西南急流和低空偏东风回流的水汽输送以及层结不稳定对这次特大暴雨的产生有重要作用.

Numerical Simulation of a Rainstorm in Southwestern Shandong Province with MM5V3

A heavy rain event occurred on 2003-08-25 in the southwestern Shandong Province is simulated with the numerical model MM5V3. The results indicate that the MM5 model simulated the rainstorm and the development of the mesoscale system successfully. The event occurred at the stream convergence area of a low-level jet and east wind circumfluence. The length of the convergence area was about 800 km from west to east. The convergence of warm and cold air induced the strong ascending motion; the lower-level jet was enhanced, transport- ing large quantities of warm, moist air into the system; and east wind circumfluence transported large quantities of cold, moist air into the system. Furthermore, due to the coupling between upper- and lower-level jets and the associated lower convergence and upper strong divergence, the continuously developing mesoscale system resulted in the heavy rain in southwest Shandong Province.