江西北部地区一次大暴雨过程湿Q矢量诊断分析

Diagnostic Analysis of Wet-Q-Vector during a Heavy Rain Process in North Jiangxi

利用NCEP提供的FNL资料和ECMWF提供的逐小时降水资料,从湿Q矢量散度、湿Q矢量锋生函数以及湿Q矢量在以等温线为参照线的自然坐标系中分解(PT分解)函数三个方面,对2019年5月12日发生在江西省北部地区的一次大暴雨天气过程进行了分析。结果表明:暴雨初期,关注低层湿Q矢量散度场的辐合中心,可以预报未来6 h后暴雨的可能落区,当这些落区中层辐合开始加强为辐合中心,则基本可以判定为暴雨中心区域;低层湿Q矢量锋生函数有助于确定雨区范围,中层的湿Q矢量锋生函数对强烈的冷暖气流交汇反映更为明显,有助于进一步确定强降水中心位置。在强降水初期大尺度的强迫作用是垂直运动发展的主导因子,而在强降水旺盛时期中尺度锋生作用占主要作用,在暴雨发展的不同阶段可以重点关注不同尺度天气特征对暴雨形成发展的影响。

Based on the FNL data of NCEP and the hourly precipitation data provided by the ECMWF,the weather process of a heavy rain process in northern Jiangxi occurred on May 12,2019 was discussed according to the wet-Q-vector divergence distribution,wet-Q-vector frontogenesis function and the decomposition of wet-Q-vector in natural coordinate system with isotherm as reference line(PT decomposition).The results showed that in the early stage of the process,the possible heavy rain areas in the next 6 hours can be forecasted by focusing on the convergence center of the shallow wet-Q-vector divergence field.When the middle convergences of these precipitation areas started to strengthen into the convergence centers,they can be determined as the precipitation central areas basically.The shallow wet-Q-vector frontogenesis function helps to determine the scope of the precipitation areas.The middle layer of the wet-Q-vector frontogenesis function was more sensitive to the strong interaction between cold airflow and warm airflow,which helped to further determine the location of the heavy rain center.In the early stage of a severe precipitation,the large-scale forcing effect was a dominant factor for the development of vertical movements.The mesoscale frontogenesis played a major role during the period of heavy rain.In different stages of rainstorm development,we can focus on the influence of different scale weather processes on rainstorm.