2014年5月下旬江西省西部区域暴雨天气过程分析

Analysis on the Regional Torrential Rain Process in Western Jiangxi during the Last Third of May 2014

利用地面气象观测资料、FY-2E卫星资料、多普勒雷达资料和NCEP再分析资料,对2014年5月24—25日江西省西部地区的暴雨天气过程进行诊断分析。结果表明:1)500 hPa高度层上副热带高压边缘短波槽东移所携带的冷平流和南方不断增强的暖湿气流的对峙导致暴雨发生。强的热力不稳定、中等偏强的垂直风切变、低层充沛的水汽供应,以及较强的辐合抬升是此次大暴雨发生的环境场特征。2)中尺度锋区触发了中尺度系统的生成,不断增强的低空西南急流、高空槽对应的正涡度区及低空急流顶端对应的正涡度区,高空强辐散和低层强辐合导致的垂直上升运动为中尺度系统的发展提供源源不断的水汽、不稳定能量和动力抬升条件。3)多个MCC生成发展并稳定少动,对流单体呈带状分布,其依次通过暴雨区形成的"列车效应"是导致大暴雨发生的主要原因;高空短波槽东移导致MCC转变成MCS,致使暴雨趋于结束。4)高空短波槽的东移、中低层西南气流的阶段性加强与强降水的发生时间吻合,而地面东风的出现和加强,为更大的垂直风切变提供很好的条件,从而导致暴雨天气的发生。

Based on conventional meteorological observation data,satellite data,Doppler radar data,wind profiler radar data,rainfall auto-gauge data and NCEP FNL reanalysis data,the severe rainstorm process happened during 24-25 May 2014 in western Jiangxi was analyzed in this paper.The results showed that：1）The confrontation between the cold temperature advection from the trough beyond the 500 hPa subtropical high and the transportation of warm and wet air originated from the southwest was the main cause for the torrential rain.Strong thermodynamic instability,medium to strong vertical wind shear,abundant supply of water vaper and strong convergence and uplifting motion were the environmental figures of this strong rainfall process.2）The mesoscale front triggered the generation of mesoscale convective systems,and the southwest low-level jet provided a continuous supply of water vapor and instability energy.3）With favorable conditions,the MCCs beyond subtropical high caused the rainstorm of Jiangxi.The favorable ambient field for this event was formed by strong thermal instability,strongvertical wind sheer,plentiful water supply and moderate convergent lifting.4）The cooperation between multi-scale systems caused strong ascending motions.Strong divergence in higher-levels and convergence in lower-levels were coupled with the development of mesoscale convective system.