新疆一次罕见的暖区暴雨过程特征分析

Analysis of a Rare Warm-sector Rainstorm Process in Xinjiang

2018年7月31日新疆出现了一次罕见的暴雨过程,最大暴雨中心位于新疆东部哈密市,哈密市伊州区沁城乡小堡村过程累计雨量115.5 mm,连续2个时次小时雨强29.2 mm。对比哈密市建站以来6个国家气象站历年资料发现,此次暴雨特征与以往冷锋暴雨明显不同,暴雨降水时段更为集中,强度比冷锋暴雨更强,暴雨云团为典型的中尺度云团,范围小、呈块状。由于500 hPa西太平洋副热带高压偏西偏北,高空无低值系统和冷空气入侵,哈密市主要受西太平洋副热带高压外围偏南暖湿气流的影响,此次暴雨结合了南方副热带高压型和偏南风风速辐合型暖区暴雨的典型特征,具有暖区暴雨的热力结构和风场配置,是一次罕见的暖区暴雨过程。暴雨区偏南风风速辐合和暴雨区山区地形的抬升效应是本次暴雨重要的触发机制,700 hPa孟加拉湾和日本海南部两支水汽在华北平原汇合沿东南输送路径至暴雨区且有强烈水汽辐合。暴雨发生在云顶亮温(TBB)等值线密集区梯度最大处,越接近TBB低值中心梯度处的暴雨强度越强。

A rare heavy rainfall occurred in Xinjiang on July 31st,2018.The largest rainstorm center was located in Hami city,eastern Xinjiang.The accumulated rainfall during the process of Xiaobao village,Qincheng township,Yizhou district,Hami city was 115.5 mm,and the hourly rainfall intensity was 29.2 mm for two consecutive hours.Comparing the historical data of six national weather stations since the establishment of the Hami city,it was found that the characteristics of this storm rain were significantly different from previous cold front heavy rainfall.The rainfall period was more concentrated and the intensity was stronger than the cold front heavy rainfall.The storm clouds were typical mesoscale clouds and the range is small and lumpy.We found that the position of west Pacific subtropical high consistently was farther and north than ever before at 500 hPa,and there is no lowpressure system and cold air invasion at upper air.Hami city is mainly affected by the southerly warm and wet air around the subtropical high of western Pacific.The rainstorm combined the typical characteristics of south subtropical high and southerly wind convergence type warm-area rainstorm,The weather process has the thermal structure and wind field configuration of warm region rainstorm,which was a rare warm-region rainstorm process.The southerly wind speed convergence in the rainstorm area and the uplift effect of the mountainous terrain in the rainstorm region were the important trigger mechanism of the rainstorm.Two water vapor of 700 hPa converge on the north China plain along the southeast transportation path to the rainstorm area and have strong convergence.Shorttime heavy rainfall occurred at the region where the contour density gradient of temperature of black body(TBB)was the greatest,and it closer to the low central gradient of TBB,the rainstorm intensity was stronger.