陕西榆林一次大暴雨天气的中尺度分析

目的]分析陕西北部榆林市一次区域性暴雨天气过程。方法]利用常规气象资料、卫星云图和ncep1°×1°再分析产品,从环流形势、中尺度系统、水汽和动力条件等方面,对2011年7月1～3日陕西北部榆林市一次区域性暴雨天气进行综合分析。结果]副高在福建形成高中心,其外围西南气流持续存在,提供了暴雨区长久的水汽输送;高原槽东移,提供了暴雨区的动力场;东北路回流冷空气与低空急流辐合是暴雨的触发机制;暴雨区与中尺度低压密切相关,暴雨出现在中尺度低压前部的低空急流中;高空槽云系和低空急流云系叠加增强,生成暴雨云团,云顶亮温TBB<-90℃。结论]该研究为今后暴雨的预报提高了理论依据。

Mesoscale Analysis of a Heavy Rainstorm in Yulin City of Northern Shaanxi

Objective] The study aims at analyzing a regional rainstorm in Yulin City of northern Shaanxi. Method] Based on conventional meteorological data, from the aspects of circulation pattern, mesoscale system, water vapor and dynamical conditions, a regional rainstorm oc- curing during July 1 -3,2011 in Yulin City of northern Shaanxi was discussed. Result] There was a small closed subtropical high near Fu- jian, around which southwest air flow existed constantly, providing water vapor for rainstorm areas for a long time ; plateau trough moved east- wards, which provided dynamical field for rainstorm areas; the convergence between northeast cold air and low-level jet flow triggered this rainstorm ; rainstorm areas were closely related to mesoscale low-pressure, and the storm appeared in the low-level jet flow in front of mesoscale low pressure; cloud systems in upper trough and low-level jet flow combined, increased and generated rainstorm cloud cluster, while brightness temperature on the top of clouds was below - 90 ℃. Conclusion] The research could provide theoretical foundation for forecast of rainstorms in future.