地形对低涡大暴雨影响的数值模拟试验

Numerical Simulation of the Topographic Effects on Torrential Rain with South west China Vortex

用 MM5模式对 1 998年 6月 2 8～ 2 9日长江三峡及其附近的低涡大暴雨过程作了初步的模拟研究。通过两种地形方案模拟的对比表明 ,四川盆地东侧山地对西南低涡的产生没有明显影响 ,但对这次低涡暴雨的强度及其分布有重要影响 ,主要表现在 :涡前暖湿气流受大巴山 -神农架山脉拦截形成迎风麓大暴雨带 ,鄂西南山区南坡也有迎风坡暴雨区 ,降水系统在东移过程中受盆地东侧整个山体阻滞迫使上游降水显著增强 ,下游降水明显减弱。

The torrential rain brought about by a South west China vortex in Changjiang Gorges and its vicinity in 28—29,June 1998 was simulated using MM5.Comparing the two simulations with different model topography schemes,it is indicated that the mountains in east Sichuan Basin has no significant effects on the genesis of South west China vortex,but has important influence on the intensity and the feature of distribution of the heavy rain events.Mainly, the warm and wet flow was blocked by Daba Shenonggia mountain range and resulted in a torrential rain bend to the windward foot of the mountain range,which was also a heavy rain region at the windward slope of the southwest Hubei mountainous district,and the east moving precipitation system was detained by the mountains in east of the basin, as the sequence, the precipitation strengthened upstream and weakened downstream.