关键词: 短时暴雨, 斜压锋生, 不稳定条件

Abstract:

Based on the conventional observation data, automatic stations precipitation and NECP reanalysis data, the causes about a short time rainstorm were analyzed comprehensively which occurred in Minxian of Gansu on 10 May 2012. The results show that the influencing system of the local rainstorm causing severe disaster presented significant baroclinicity. The stronger cold advection behind trough and warm advection in front of trough on 500 hPa converged intensively, and its frontogenesis was obvious from ground to 500 hPa. Instability condition caused by baroclinic frontogenesis was a key factor leading to strong convection. From the point of configuration of the weather system, the baroclinic trough on 500 hPa, vortex shear and warm advection on 700 hPa, and surface cold front were influencing systems of this strong convective process. The diagnosis of physical quantities shows that the frontogenesis function enhanced significantly in the afternoon on 10 May, the mesoscale rain cell appeared in front of the frontogenesis region, and the gradient direction of the frontogenesis function was the moving direction of the mesoscale rain cell. During this strong convection process, the atmospheric stratification was conditional instability, and the temperature difference between 700 and 300 hPa was up to 49 ℃. The baroclinic frontogenesis increased gradually during the process, which resulted in enhancement of instability condition and development of ascending motion. It was the root cause of the short-term rainstorm

Key words: short time rainstorm, baroclinic frontogenesis, instability condition