南疆西部沙漠边缘汛期两次罕见暴雨过程诊断分析

Diagnosis analysis on the two rare rainstorms occurred in flood season in edge of Taklimakan desert in southwest Xinjiang

应用常规观测及NCEP再分析资料(水平分辨率1°×1°,间隔为6h),着重从暴雨发生的环流配置、影响系统、水汽及动热力条件入手,对2010年6月6日和2011年5月30日发生在南疆西部沙漠边缘皮山县汛期的两次历史罕见暴雨过程进行了诊断分析。结果发现:高空200hPa上中亚及中亚南部西南急流、低空700(850)hPa上南疆盆地偏东急流并存,中空500hPa上南支槽和低空700(850)hPa上喀什至和田切变线是皮山暴雨发生的环流配置和主要影响系统;暴雨过程中存在和显著增大的比湿、中低层强烈的水汽辐合以及自皮山西部、南部持续输入的水汽为其发生提供了充沛的水汽条件;垂直螺旋度较好地反映出了暴雨在时间上的变化,且中层500hPa负值、高低层上"-+"或"+-"的配置结构揭示了暴雨过程强烈上升运动的发生;湿位涡、锋生函数在对流层低层的时空变化对暴雨预报有一定的指示性,暴雨过程中对流层低层MPV1<0,MPV2>0,锋生函数有锋消向锋生过程的转变,暴雨出现在MPV2>0的分布区内、锋生最强时刻的6小时后。

Based on conventional observation and NCEP/ NCAR 1°×1°reanalysis data, two historic rare rain- storms processes occurred on June 6th 2010 and May 30th 2011 were analyzed. The results showed that the major effect system of two rainstorms was 500hPa＇s southern trough on aloft and 700 （850） hPa＇s shear at low - level ; sig- nificant increase of specific humidity and low - rise strong water vapor convergence and the continued water vapor input from western and southern Pishan＇s were provided abundant moisture conditions to heavy rain processes; the vertical helicity well reflected the time changes of rainstorms;the configuration structure of a negative value at 500hPa and＂ - ＋ ＂or＂ ＋ -＂ on high and low level revealed the strong rising motion ;time and space＇s changes of moisture potential vorticity and frontogenesis function in lower troposphere had certain telltale for forecasting rainstorm; MPV1 〈 0, MPV2 〉 0 and frontogenesis function had a transform process from frontolysis to frontogen- esis in lower troposphere in the process of rainstorm;rainstorm happened in the area of MPV2 〉 0 and strongest moments of frontogenesis after 6 hours.