1998年夏季江淮地区强暴雨过程的湿位涡诊断分析

Diagnostic analysis of MPV for torrential rain in Jiang-huai basin in summer of 1998

为了研究梅雨期江淮流域暴雨发生发展的特征,利用HUBEX资料,根据湿位涡守恒原理和倾斜涡度发展理论,分析了江淮地区2次强暴雨的发生发展的原因。结果表明:2次暴雨是在不同性质的层结状态下发生的,其湿位涡的分布有较大差异。在局地对流稳定条件下,暴雨区上空对流层中、低层Pm1>0,Pm2<0,并且Pm1>Pm2,对流层中、低层的垂直风切变和大气的斜压性使垂直涡度显著发展,导致暴雨发生。在局地对流不稳定的条件下,暴雨区上空对流层中、低层Pm1<0,Pm2>0,也满足Pm1>Pm2,暴雨过程是对流不稳定和斜压不稳定共同作用的结果。无论是对流稳定或不稳定的强降水过程,Pm1和Pm2均能反映出降水的触发机制和特征,对于暴雨的预报和诊断具有指导意义。

In order to research the character of rainstorm in the Changjiang - Huaihe basin, the characteristics of MPV in the two different processes of heavy rain over the Changjiang - Huaihe basin in summer of 1998 were analyzed. With the concept of moist potential vorticity （MPV） and GAME/HVBEX data, the result showed that two torrential rain processes occurred in different stratification state. Under local convective stable, in middle and low troposphere over rainstorm, the increase of vertical shear of horizontal wind and moist baroclinity can result in the increase of vertical vorticity, so rainstorm occurred. Under local convective unstable, in middle and low troposphere over rainstorm, the heavy rain is the result of combined action of convective unstable and baroclinic instability.