关键词: 大暴雨, 不同尺度系统, 涡旋云系, 复杂回波

Abstract:

Based on conventional observation data, meteorological data observed by automatic encrypted weather stations, satellite images and radar mosaic products, the heavy rainfall occurring in Shanxi from 18 to 20 July in 2016 was analyzed. The results are as follows: (1) The continuously heavy rainfall in Shanxi was caused by the steady circulation situation on 500 hPa and ground, the strong convergence and vertical updraft was caused by a meso-scale shear line and more moisture was transported to Shanxi by low level jet. (2) The process was caused by the vortex structure cloud which was developed by the baroclinic leaf cloud. The radar echoes showed convective cloud and the stratiform cloud, and there were several convection cells development, merging, strengthening and disappearing in the stratiform cloud. The whole process could be divided into two stages, at the first stage, it was mainly the zonal echo with several convective echoes on it, which caused thunderstorms and short-time strong rainfall. During the second stage, the radar echo intensity decreased and convection activity abated, while the radar echoes kept growing and decaying and long lasting, which resulted long time stable rainfall.  (3) During the rainstorm process, the stable maintaining of synoptic-scale system made the meso-scale system  stable, sustained developing and strengthening through the block role of the meso-scale low vortex and the continuous supply of the cold air. The formation and maintenance mechanism of the meso-β-scale or meso-γ-scale convergence system were restricted by the meso-α-scale low vortex system, and these smaller scale systems were the direct factors of the heavy rainfall.

Key words: torrential rainfall, multi-scale system, vortex structure cloud, complex radar echo