长江下游一次大暴雨的中尺度模拟分析

运用中尺度数值模式（MM5V3.6）对2004年6月25日长江下游地区一次大暴雨天气过程进行了数值模拟,结合天气形势和卫星云图对此次过程进行了分析.结果表明：在东北冷涡和西太平洋副热带高压两大天气尺度系统的作用下,西南低空急流的再次加强和中低层切变线共同作用是此次大暴雨过程的主要原因.螺旋度分析表明,在不均匀的强上升气流的作用下,涡旋的水平分量向垂直分量转化是此次强降水的可能机制之一.

Simulation to Mesoscale Heavy Rain in the Lower Valley of Changjiang River

A heavy rainfall event in the lower valley of Changjiang river on 25 June 2004 is simulated by the mesoscale numerical model MM5 and is analyzed with the synoptic charts and satellite imagire. The results indicate that under the favorable weather background, it is caused by the strengthening again of the southwest low level jet and the movement of the low level shear line. The analysis of helicity also revealed that under the updraft, the conversion from the horizontal whirlpool into the vertical whirlpool is one of the possible mechanisms of the event.