2008年6月广西持续性暴雨的诊断与数值模拟

Diagnosis and numerical simulation of the persistent heavy rainfall in Guangxi in June 2008

用NCEP/NCAR全球逐日再分析格点资料和广西区域日降水资料,对2008年6月12—13日发生在广西的持续性暴雨过程进行了诊断分析,并利用中尺度数值模式WRF进行了数值模拟研究。结果表明:暴雨过程的水汽来源主要为孟加拉湾南部和南海北部;在强降水期间,暴雨区上空低层为较强的大气层结不稳定区,中高层为大气层结相对稳定区,不稳定能量与降水强度有着很好的对应关系;西南急流作为对流系统上升的触发机制,为广西持续性暴雨过程的发生和发展提供了水汽条件和动力条件。WRF模式成功模拟出本次暴雨过程的大尺度环流形势的演变及中尺度降雨分布,本次暴雨与850hPa上一个β中尺度低涡的生成和强烈发展直接关联。

A diagnostic analysis and numerical simulation of persistent heavy rainfall in Guangxi is performed by using the daily precipitation data of Guangxi area and the NCEP/NCAR reanalysis daily data and the mesoscale model WRF. The results show that moisture came mainly from the south of Bengal and north of south China sea. There is the unstable stratification at low level while the relative stable stratification at middle and high levels over the rainfall area and there is a good relationship between the unstable energy and rain rate. As a trigger mechanism of the increase of convective system,the southwestern jet provided the occurrence and progression of the persistent heavy rainfall water vapor and dynamic condition. WRF model could successfully simulate the changing of large scale circulation and the distribution of meso-β scale rainband. This persistent heavy rainfall is in direct relationship with the genesis and intensive development of a mesoscale low vortex at 850 hPa.