2011年7月初一次大暴雨过程分析

The Analysis of a Heavy Rain Process in July 2011

2011年7月初四川中部至东部出现一次持续的强降水过程,采用NCEP再分析资料、常规观测资料、自动站资料和FY-2E资料对此次过程进行诊断分析。结果表明,本次区域性大暴雨过程主要影响系统为副高外围西南气流和中尺度对流云团,副高西伸带来充沛的暖湿气流向川内输送,与北下干冷空气在四川上空汇合,增强大气层结不稳定;雨区上空对流层内有强上升运动且中低层不稳定呈高温高湿状态;700hPa水汽通量散度分析显示本次暴雨水汽源于孟加拉湾,水汽辐合区内有TBB大值中心及视热源、视水汽汇大值区;本次降水为对流性降水,水汽凝结加热对大气加热起重要作用,视热源、视水汽汇及垂直螺旋度与暴雨有很好的对应关系,当强降水出现时螺旋度呈(高空)上负(低空)下正分布,高层负螺旋度的生消与降水有更好的对应关系;雨区上空水汽收支显示南、北两边界是主要水汽来源,且水汽以南北向辐合为主。

A heavy rain process occurred in central and eastern Sichuan province in early July 2011, diagnostic analyses are given by using NCEP reanalysis data, routine sonde and surface observation data, automatic weather station data and black body temperature data of FY -2E meteorological satellite. The analysis results show that, the mainly affect system of the regional heavy rain is southwest airflow around the subtropical high in West Pacific and mesoscale convective cloud cluster, the subtropi- cal high extends westward meanwhile brings abundant warm and humid air flow to Sichuan, confluent with dry and cold air from north in Sichuan province, which enhances unstable atmospheric stratification; the rain areas have ascend motion and in low - level instability was hot and humid; 700hPa moisture flux divergence analysis showed that the rainstorm water vapor is from the Bay of Bengal, and in the moisture convergence zone there is big value of TBB, apparent heat source and apparent moist sink ; analysis of apparent heat source and apparent moist sink suggests that this process is a convective process, and condensation heating plays an important role in the atmospheric heating. Apparent heat source, apparent moist sink and vertical helicity have good correspondence between the rainstorm. When heavy precipitation occurs helicity is negative at higher levels and positive at lower levels; the water vapor budget over rain area shows that both north and south border are the main moisture sources, and the moisture supply is mainly from the convergence of north and south boundary.