一次引发四川盆地南部暴雨的西南低涡湿旋转量分析

利用NCEP逐日资料和常规观测资料对2009年7月30~31日一次四川盆地南部强降雨过程进行诊断分析。结果发现:西南涡在700hPa上表现得比较明显,当发展极强时,甚至在500hPa也出现闭合环流;西南低涡涡区内均有降水发生,强降水中心位于涡区东北侧。低层水汽通量散度负值辐合区的分布不仅对相应时段降水落区指示较好,而且对于未来6h雨区分布也有一定参考性,可作为短临预警指标。强降雨区与强正涡度辐合上升运动区有较好的对应关系,对流层低层湿位涡的负值区对降水落区指示较好,强降水区出现在中高层正值MPV1下沿最强区,以及MPV2正负值交界区。

Wet Rotation Analysis of Southwest Vortex Causing a Heavy Rain in Southern Sichuan Basin

Based on the 6-hour-interval reanalysis data with 1.0°×1.0°resolution from NCEP/NCAR, station observational data and so on, a heavy rainfall during July 2009 are analyzed.The results show that the southwest vortex on 850hPa is more obvious, the heavy precipitation is to the southwest of the southwest vortex, and the heavy precipitation field has a good relation to the strong ascending motion.The heavy precipitation is in the negative field of moisture potential vorticity, the vertical component of wet vorticity could show the combined effect of atmospheric rotation and water vapour transport.It also has a good correspondence with rainfall and provides a new way for determining the variations of rainfall.