新疆一次罕见的暖区暴雨过程特征分析

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 h Pa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。

Comprehensive Analysis of the Extreme warm-sector Torrential Rain Process in Hami City, Xinjiang

This paper analyzes the strongest and most influential rainstorm process in Xinjiang Hami on July 31, 2018. Comparing with rainstorms in the previous years, it is found that the rainstorm is the extreme warm-sector torrential rain . Combined with the characteristics of the warm-sector rainstorms of the subtropical high and the south wind speed convergence type, we find that the position of western subtropical high consistently is farther west and north than ever before at 500hPa,This weather process has the thermal structure and wind field configuration of the typical warm region rainstorm, and the southerly wind speed convergence in the rainstorm area and the uplift effect of the mountainous terrain in the rainstorm region are the important trigger mechanism of the rainstorm. Two water vapor of 700hPa converge on the north China plain along the southeast transportation path to the rainstorm area and have strong convergence. Short-time heavy rainfall occurs at the region Where the contour density gradient of Temperature of Black Body(TBB) is the greatest, The stronger the rainstorm intensity is the closer it is to the low central gradient of TBB.