湖南一次强降水天气过程分析

综合运用常规、非常规加密观测资料、风云卫星资料和1°×1°的NCEP/NCAR再分析资料,对2019年主汛期湖南一次强降雨过程进行分析及成因探讨。结果表明:此次降雨过程影响系统复杂多变,由暖区暴雨、中层冷平流入侵暴雨、锋面暴雨组成,冷空气入侵时降雨效率最高,小时雨强与累计降雨达到最强;副高明显偏强,较历年同期偏西24个经度,其边缘多短波槽活动,高空冷涡活动明显,冷涡与冷槽同位相叠加,槽底往南发展至30°N以南,其后部偏北气流引导冷空气渗透南下与副高边缘西南气流交绥,是持续强降水的大尺度环流背景;中小尺度系统活动频繁,多个中尺度对流复合体(MCC)发展合并,直接造成暴雨天气;雷达回波图可看出低质心降水的特征,降雨效率高;强降水发生时散度场空间分布和垂直速度对应较好,强上升中心与无辐散层相对明显。

Analysis of a Heavy Rainfall Process in Hunan

By using the conventional and unconventional intensive observation data, FY satellite data and NCEP/NCAR reanalysis data (1°×1°), a heavy rainfall process happened in Hunan in the main flood season of 2019 is analyzed and its causes are discussed. The results show that: the influence systems of this rainfall process were complex and changeable, which were composed of the warm zone rainstorm, middle cold advection intrusion rainstorm, and frontal rainstorm. The highest rainfall effectiveness occurred when the cold air invaded, and the strongest hourly rainfall intensity and accumulated rainfall reached the peak; the subtropical high was obviously strong, 24 longitudes west than the same period of previous year, and there were multiple active short wave troughs around. The upper cold vortex activity was obvious, and the cold vortex and cold trough were superimposed in the same phase. The bottom of trough developed southward to the south of 30°N, and the northerly airflow at the back of the trough guided the cold air to penetrate southward and intersect with the southwest airflow at the edge of the subtropical high, which was the large scale circulation background of continuous heavy rainfall. Frequent activities of medium and small scale systems and the development and merger of multiple MCC (Mesoscale Convective Complex) directly caused the rainstorm. The radar echo map shows the characteristics of low centroid precipitation and high rainfall effectiveness. When heavy rainfall occurred, the spatial distribution of divergence field and vertical velocity corresponded well, and the strong rising center and the non divergence layer were relatively obvious.