Abstract:Based on hourly and 5 min observation data of automatic weather station, SWAN mosaic product of radar composite reflectivity in the middle reaches of the Yangtze River and NCEP FNL reanalysis data, the characteristics of four convective storms with low-echo-centroid of short-term heavy precipitation in Wuhan are analyzed. The results show that the characteristics of convective system induced by different weather backgrounds are different. Under the background of baroclinic instability caused by low-level warm forcing, the environmental conditions are high energy and high humidity, and the accumulation of thunderstorm cold pool is conductive to triggering linear severe convection in the stable precipitation front. Under the baroclinic frontogenesis background, the convergence of cold and warm air is intense, strengthening the baroclinicity; there are more mesoscale cyclonic waves on the ground, and the stable precipitation in the front area is often accompanied by a short-time heavy rainfall. Under the quasi barotropic background, the baroclinic atmosphere is weak, but the high-energy and high-humidity environment as well as the near-surface flow field forcing and local thermal difference are easy to trigger severe thermal convection activities. In addition, according to the radar echo characteristics and precipitation characteristics of convective storms, the TS (trailing stratiform cloud) type moves faster, resulting in a small range of short-time heavy rainfall. Quasi-stationary type shows that the echoes of large-scale stratiform cloud with zonal trend are stable, and there are multiple cumulus convective echoes in the middle. The precipitation enhancement in each stage corresponds to the new convective cell passing through Wuhan Station. The consolidation type is in the circulation when the waves merge, often accompanied by the occurrence of heavy rainfall, and the echo shape and direction after merging affect the intensity and duration of precipitation. Actually, under different environmental backgrounds, triggering inducement and organizational form, the surface meteorological elements before and after the occurrence of short-time heavy rainfall show different change characteristics. The different fronts and convection triggering positions lead to different changes in temperature. Ground mesoscale system plays an important role in triggering and organizing the development of mesoscale convective system (MCS). Its generation, elimination and transformation usually have a certain advance in time for MCS. So, paying attention to the development and evolution of ground mesoscale systems such as ground convergence line and temperature front area is of great significance for predicting the triggering and organizational evolution of MCS.