Abstract:

Based on the conventional observations，NCEP / NCAR reanalysis data，FY － 2E satellite images and radar data，the synoptic analysis and physical field diagnostic analysis methods were used to explore the triggering mechanisms and vapor sources of the heavy rainstorm that occurred in Northwest China． By analyzing circulation patterns，vapor，dynamic and unstable conditions，the results show that the southwestern low level jet and the eastern low level jet played significant roles during the heavy rainfall process，they brought abundant water vapor and unstable capability． Forward trough and warming humidification in the low layer made stratification convective instability．The overlay of convergence line on 700 hPa and the shear line on 850 hPa was the triggering condition，which resulted in the release of unstable capability and induced the heavy rainstorm． Meanwhile，convergence at low level and divergence at upper － level formed upward motion over the entire layer，which was the dynamic condition．The study not only provides focus for forecasting heavy rainstorms in arid Northwest China，but also supplies references to control flood and mitigate disasters for local government．

Key words: heavy rainstorm in arid area, diagnostic analysis, circulation pattern, low level jet

摘要：

利用常规观测资料、美国环境预报中心逐6 h FNL(1°×1°)再分析格点资料、NCEP/NCAR(2．5°×2．5°)逐6h再分析资料、FY－2E气象卫星资料和雷达回波资料，用天气学分析和物理量场诊断分析方法，探究了2012年6月4～5日发生在新疆库尔勒至甘肃玉门一带干旱地区60 a一遇的大暴雨天气过程的水汽来源以及触发机制。结果表明:中层强盛西南低空急流和低层偏东低空急流为暴雨区源源不断地输送水汽并带来不稳定能量;前倾槽结构和低层增温增湿，形成大气层结强烈对流不稳定；低层切变线(850 hPa)和其上空辐合线(700 hPa)叠加，导致不稳定能量释放，诱发大暴雨天气过程发生；低空辐合高空辐散，形成整层上升运动，为大暴雨的发展和维持提供了动力条件。

关键词: 旱区大暴雨, 诊断, 环流形势, 低空急流