干旱沙漠区一次局地极端大暴雨的分析

A Local Extreme Rainstorm Process in Arid Desert Area

为了提高干旱沙漠区极端降水天气的预报预警能力和缓解该地水资源严重短缺问题,利用常规观测图、区域自动站雨量、FY-2D云图、单站气象要素和NCEP再分析资料,对2013年5月15日干旱沙漠区民勤县局地极端大暴雨的成因进行诊断分析。结果表明:此次局地大暴雨具有出现时间特殊、雨强大、酝酿时间长,且发生在降水极少的干旱沙漠区的特点。主要影响系统是500 h Pa新疆低槽引导冷空气南下,中低层切变线缓慢东移,配合地面风场辐合;水汽输送通道有西南和东南2个,东南急流引导的水汽是此次过程主要的水汽来源。中低层辐合、高层辐散及整层上升运动是这次大暴雨的动力条件;K指数、CAPE指数、Si指数的大值区、θ_(se)高能舌延伸位置偏北偏东与此次大暴雨区相符;2个中尺度对流云团的合并发展是造成此次大暴雨的重要原因。

The paper aims to improve the forecast ability of extreme rainstorm in arid desert area and alleviatethe local water resource shortage. The authors used the maps of conventional meteorological observation,precipitation of regional automatic weather stations, FY-2D satellite cloud pictures, meteorological elements ofsingle station and NCEP reanalysis data to analyze the cause of a local extreme rainstorm happened on 15 May2013 in Minqin of the arid desert area. The results showed that： this local rainstorm happened in the arid desertarea which had very little precipitation, the rainstorm had the characteristics of special time, large rainfallintensity and long brewing time. The 500 h Pa Xinjiang trough leading the cold air southward, low-shear linemoving slow eastward, and ground wind field convergence were the major system which affected the extremerainstorm. The water vapor gathered in southwest and southeast direction, the southeast jet was the mainsource. Low-level convergence, high-level divergence and the whole layer ascending motion were the dynamicconditions; the high value areas of K index, CAPE index and Si index, the high energy tongue areas of θsestretching position north by east were coincided with the rainstorm area; the combination and development oftwo convective cloud clusters was the important cause of the rainstorm.