倾斜涡度发展与β中尺度低涡

利用中尺度暴雨模式MRM1，对1998年7月21、22日湖北黄石的β中尺度低涡及特大暴雨进行数值模拟，采用湿位涡守恒原理对模式输出的高时空分辨率物理量场进行分析。结果表明，β中尺度低涡是在低层θ水平梯度加大，θe等值线变得更加倾斜、近似陡立而发生SVD的情况下产生的。Pm1在本次特大暴雨过程中是主要的，大大超过pm2，低层对流稳定度绝对值的迅速减小造成垂直涡度的急剧增大，从而形成β中尺度低涡。因此，θe等值线变得陡立可能是气旋性涡度激烈发展导致对流性特大暴雨形成的一个重要原因。

Slantwise Vorticity Development and Meso-BScale Low Vortex

Numerical simulatio n is made for ex t remely heav y rain and meso-B scale low vortex in Huangshiof Hubei pr ovince during 21-22 July 1998 using a meso scale rainsto rm model MRM1. High spat ial andtempor al reso lut ion model-output physical f ields are analyzed according to the co nser vation principle ofmoist potent ial vo rticity . T he meso-B scale low vortex occurred under the condit ion of occurring slantw isevor ticity development ( SVD) w hich is due to the incr easing ho rizontal gradient of low -level He and moreslant near steep He isotaches. T he analyses using the conservat io n principle o f moist potent ial v ort icityshow that p m1 is principal and it ex ceeds p m2 great ly. T he v ert ical vort icity increases r apidly because of therapidly decreasing of abso lute v alue o f low -level condit io nal instability, and then meso-B scale low vo rtexfo rms. So He the steep change of iso taches must be an important reaso n for the fo rmat ion of convect ive extremely heav y rain due to rapid development o f cyclonic vort icity