一次高原低涡东移引发四川盆地暴雨的诊断分析

Diagnostic Analysis of a Heavy Rainfall in Si-chuan Basin Induced by Plateau Vortex Moving Eastward

摘要: 本文采用中国自动气象站与CMORPH卫星融合的降雨量资料、NCEP FNL再分析资料以及FY-2E相当黑体亮温资料，对2014年7月四川的一次暴雨天气进行诊断分析。结果表明：1) 此次暴雨产生于高原低涡东移出高原，其南部向四川盆地分裂出低槽的过程中。主要降雨区位于低槽前部，降雨带呈西南至东北走向；2) 暴雨过程中，副热带高压西伸至四川东南部，其外围偏南风向暴雨区持续提供水汽。暴雨区处于水汽辐合区，暴雨中心低层存在的不稳定能量区为暴雨的产生与发展提供充足的水汽与能量；3) 在暴雨开始前期，高原低涡东侧和东南侧低层700 hPa存在一正涡度平流区。这表明低层的正涡度得到发展，风场的辐合增强，上升运动得到发展，从而有利于强对流活动的产生，造成降水过程。这有可能是此次四川盆地暴雨过程产生的动力原因。从视水汽汇分析可知，在暴雨过程中，暴雨区中低层视水汽汇发展明显，而在暴雨后期暴雨区低层出现视水汽汇负值分布。这表明降水过程中所释放的潜热增加，加热大气，继而大气反过来作用于系统的维持与发展。这有可能是此次暴雨过程维持的能量原因。

Abstract: By using the fusion precipitation data of China automatic meteorological station and the Climate Prediction Center morphing technique (CMORPH), the National Centers for Environmental Prediction (NCEP) reanalysis data and the temperature of black body (TBB) data from the Fengyun-2E (FY-2E) satellite, we analyzed a rainstorm weather which occurred from 30 July to 31 July in 2014 in Sichuan. The results show that: 1) The rainstorm occurs in the process of splitting the low trough of the Plateau Vortex to the Sichuan Basin after the Plateau Vortex moved out of the Plateau. The rain-storm is located in the front of the low trough and the rain zone is from southwest to northeast; 2) During the rainstorm, the subtropical high stretches westward to the south of Sichuan. The warm and wet air from the South China Sea is transported to rainstorm area. The rainstorm area is in the water vapor convergence zone and the low layer of the rainstorm center is in the state of convective unstable stratification, which provide favorable water vapor and thermal conditions for the produc-tion and development of the rainstorm; 3) There is a positive vorticity advection area on the east and southeast side of the plateau vortex 700 hPa at the beginning of the rainstorm. This shows that the positive vorticity of the lower layer is developed, the convergence of the wind field is enhanced and the rising motion is developed, which is beneficial to the production of strong convective activi-ty and the precipitation process. It may be the driving force for the rainstorm process in the Sichuan Basin. According to the analysis of the apparent water vapor sink, the apparent water vapor sink in the middle and low layers of the rainstorm area is obviously developed during the rainstorm, and the negative distribution of the apparent vapor sink appears in the lower layer of the late storm area. This shows that the latent heat released during precipitation increases and the atmosphere is heated, which in turn plays a role in the maintenance and development of the system. It may be the energy reason for the rainstorm process.