2013年南疆西部一次罕见暴雨的成因

Cause of a Rare Rainstorm in the West of Southern Xinjiang in 2013

利用新疆自动站逐小时雨量资料和NCEP（1°×1°）再分析资料,从锋生作用和湿位涡特征出发,对2013年5月26～29日发生在南疆西部罕见暴雨的成因进行诊断分析。结果表明：（1）此次暴雨过程是中亚低涡影响造成的,高空西南急流、低层偏东急流的耦合有利于次级环流的形成,对上升运动发展和水汽辐合抬升有重要作用;（2）降水出现在能量锋区上,暴雨中心位于等θse线密集且陡立的区域;（3）锋生函数与降水有很好的对应关系,锋生的强度和伸展高度与降水的强度及持续时间有非常明显的相关性;（4）暴雨发生在700 h Pa湿位涡零线附近等值线密集区,湿位涡＂上＋下-＂配置以及高湿位涡的下滑有利于对流发展和降水加强。

Based on the hourly precipitation data of automatic weather stations,NCEP reanalysis data with 1° × 1° spatial resolution,the cause of a rare rainstorm in the west of southern Xinjiang from 26 to 29 May 2013 was diagnosed and analyzed by using frontogenesis function and moist potential vorticity（ MPV）. Results are as follows：（ 1） The rainstorm was caused by the Central Asia low vortex.The coupling of upper- level southwest jet and low- level easterly jet was beneficial to the formation of secondary circulations,which played an important role to ascending motion development and vapor convergence uplift.（ 2） The rainfall mainly occurred in the energy frontal zone,and the rainstorm center was located in the dense and steep area of the θseisolines.（ 3） The rainfall was corresponded well to the frontogenetical function,and the intensity and duration of precipitation had obvious relativity with the strength and extension height of frontogenesis.（ 4） The rainstorm occurred in the dense area of isolines nearby the zero lines of MPV on 700 h Pa. The configuration of MPV with positive in upper and negative in low and the sliding down of high MPV was advantageous to the convection development and rainfall strengthening.