台风“韦帕”(0713)引发华东暴雨过程的诊断比较

采用湿Q矢量、螺旋度、湿位涡对给华东造成严重灾害的超强台风"韦帕"(0713)强降水过程进行诊断比较分析,结果表明:登陆前,上述物理量均能提前指示强降水落区,湿位涡有更多提前指示时间,螺旋度次之,湿Q矢量最少;登陆后,三者均能表征台风主体云系降水,湿位涡、螺旋度与强降水有较好对应关系,而湿Q矢量指示强降水位置偏北,但湿位涡会出现一定程度空报现象;台风深入内陆后,螺旋度预报指示明显不如湿位涡、湿Q矢量好,螺旋度指示强降水位置偏东,而湿Q矢量指示强降水范围略偏小;对台风后部强降水,湿Q矢量和螺旋度均未能预报出降水落区,而湿位涡仍有较好的预报效果。从区域平均看,螺旋度与湿Q矢量的预报指示时效小于12 h,而湿位涡超过12 h。

Comparative analysis of rainstorm course over east China induced by typhoon Wipha (0713)

Based on NCEP/NCAR 1°×1° final analysis(FNL) and surface station precipitation data,the wet Q vector,helicity,moist potential vorticity(ζMPV) were used to perform diagnostic analysis of the heavy rainfall course induced by typhoon Wipha(0713) which severely affected east China in 2007.The results show that before the typhoon landfall the heavy rainfall area of typhoon periphery can be characterized by the areas of negative wet Q vector divergence,the areas of positive helicity,and the overlap areas of ζMPV1<0 and ζMPV2>0.As far as the forecast lead time is cancerned,ζMPV1<0 and ζMPV2>0 overlap areas were the best among them,followed by helicity positive area,wet Q vector was the worst.After the typhoon landed,the precipitation area predicted by the wet Q vector was located on the north side of real area;the prediction by the method of ζMPV1<0 and ζMPV2>0 overlap areas may be false.After typhoon intrusted inland,the relationship between helicity positive area and heavy precipitation center was obviously not as good as the ζMPV1<0 and ζMPV2>0 overlap areas and the areas of negative wet Q vector divergence.The area helicity was biassed towards the east of real heavy rainfall,the scope of the areas of negative wet Q vector divergence was smaller than observation.The heavy rainfall at the rear of typhoon could not be predicted by the areas of negative wet Q vector divergence and the areas of positive helicity,while ζMPV1<0 and ζMPV2>0 overlap areas still had better prediction effect.With respect to the regional average,based on the areas of negative wet Q vector divergence and positive helicity,the prediction time is less than 12h,but in the overlay area of ζMPV1 <0 and ζMPV2>0 it was more than 12h.