Analysis of the Heavy Precipitation Weather Process in Kashgar Region from August 20 to 25, 2017

本文基于NCEP FNL再分析数据、喀什地区各气象站降水数据以及EC数值预报资料对2017年8月20~25日喀什地区大范围降水、降温天气进行诊断分析，结果表明：本次天气主要是主导系统乌拉尔山高压脊西撤，中亚低值系统分裂南北两支，南支低槽携带暖湿气流与分裂东移北上的北支系统对盆地内东灌冷空气汇合造成，200 hPa高空风速陡增的时间与出现降水的时间较为一致，500 hPa风场喀什附近有风向、风速的切变，利于低涡沿切变线东移南下，降水落区位于风向、风速切变处。850 hPa风场“冷池”的建立，使得暖湿气团被迫抬升，利于产生辐合型大降水。整个过程高压的路径是先向东南，分裂后向东北移动，底部东灌的冷空气与西方路径进入南疆西部受中天山阻挡的冷空气汇合倒流进入南疆盆地从而造成本次强降水天气。This paper conducts a diagnostic analysis of the extensive precipitation and temperature drop in Kashgar region from August 20 to 25, 2017, based on NCEP FNL reanalysis data, precipitation data from various meteorological stations in Kashgar region, and EC numerical forecast data. The results show that this weather event was mainly caused by the westward retreat of the Ural Mountain high-pressure ridge, the split of the Central Asian low-pressure system into two branches, the south branch low trough carrying warm and humid air, and the convergence with the north branch system moving eastward and northward, which brought cold air into the basin. The time of sudden increase in wind speed at 200 hPa was relatively consistent with the time of precipitation occurrence. There was a wind direction and wind speed shear in the 500 hPa wind field near Kashgar, which was conducive to the eastward and southward movement of the low vortex along the shear line. The precipitation area was located at the wind direction and wind speed shear. The establishment of the “cold pool” in the 850 hPa wind field forced the warm and humid air mass to rise, which was conducive to the generation of convergence-type heavy precipitation. The path of the high pressure was first southeastward and then northeastward after splitting. The cold air flowing eastward from the bottom and the cold air entering the western part of southern Xinjiang from the west and blocked by the Central Tianshan Mountains converged and flowed back into the southern Xinjiang basin, thus causing this heavy precipitation event.