一次局地大暴雨过程中两个不同MCS成因分析  

Cause Analysis of Two Different MCS During a Local Heavy Rainstorm

作　　者：钟敏[1] 陈璇[1] 王珊珊[1] 范元月 Zhong Min;Chen Xuan;Wang Shanshan;Fan Yuanyue(Wuhan Central Meteorological Observatory,Wuhan 430074,China;Yichang Meteorological Office,Yichang 443099,China)

机构地区：[1]武汉中心气象台,武汉430074 [2]宜昌市气象局,湖北宜昌443099

出　　处：《气象与环境科学》2020年第4期26-35,共10页Meteorological and Environmental Sciences

基　　金：湖北省气象局科技基金重点项目“分类强对流天气概率预报技术研究”(2018Z02)。

摘　　要：利用常规观测资料、地面加密自动站资料、雷达资料、湖北地形资料及NCEP、ECMWF再分析资料,针对一次数值模式漏报的局地大暴雨过程进行分析,结果表明:高空槽前,低层切变线北侧,地面弱冷空气侵入暖倒槽是本次过程的大尺度天气背景。边界层强辐合中心和订正后高对流有效位能在预报中值得关注。两个大暴雨中心分别由两个不同的中尺度对流系统(Mesoscale Convective System,MCS)造成的,其演变形式和加强维持机制明显不同。松滋地区MCS受阵风锋触发,加强于边界层强辐合中心附近,在局地锋生作用下演变为中尺度涡旋结构,雷达上表现为人字形回波形态,大暴雨中心位于人字形回波交点处,50 mm/h雨强维持3 h。长阳地区MCS在边界层辐合区边缘,受边界层辐合气流触发,由加强的偏东气流在迎风坡上产生较强的地形强迫抬升而增强,最大雨强达102 mm/h。Using the conventional observation data, ground densely-observed automatic station data, radar data and Hubei topographic data as well as the NCEP and ECMWF reanalysis data, this paper analyzes a local heavy rainstorm process which was missed by numerical models. The results show that the weak cold air entering the warm inverted trough in front of the high-level trough and on the North side of the low-level shear line was the large-scale weather background of this process. The strong convergence center of the boundary layer and the revised high convective effective potential energy deserves attention in the operational forecasting. The two heavy rain centers were caused by two different mesoscale convective systems (MCS), and the mechanisms for their evolution and maintenance were obviously different. The MCS in Songzi area was triggered by gust front and strengthened near the strong convergence center of the boundary layer. Under the effect of local frontogenesis, it developed into a mesoscale eddy, which was seen as a herringbone echo pattern on the radar image. The heavy rain center was located at the intersection of herringbone echoes, making the rainfall intensity of 50 mm/h maintain for 3 hours. The MCS over the Changyang area was at the edge of the convergence zone of the boundary layer. Triggered by the convergence flow of the boundary layer, the MCS got enhanced by the strong topographic forcing lift of the enhanced eastward wind on the windward slope, resulting in the maximum rainfall intensity getting up to 102 mm/h.

关 键 词：局地强降水 中尺度对流系统(MCS) 成因分析 锋生 地形抬升 

分 类 号：P458.1+21.1[天文地球—大气科学及气象学]