一次夜间弓形回波特征分析  

Analysis of the characteristics of a nocturnal bow echo

作　　者：陶岚[1] 袁招洪[2] 戴建华[1,3] 孙敏[1] 

机构地区：[1]上海中心气象台,上海200030 [2]上海市气象局,上海200030 [3]南京大学大气科学学院,南京210093

出　　处：《气象学报》2014年第2期220-236,共17页Acta Meteorologica Sinica

基　　金：国家自然科学基金面上项目(41175050);气象行业专项(GYHY201006002,GYHY201306010)

摘　　要：针对2012年7月13—14日一次发生在高空槽前暖湿环境中产生短时强降水和7—9级雷雨大风的夜间弓形回波系统,进行了天气过程分析和数值模拟,发现弓形回波系统由两个多单体雷暴合并发展,强降水特征明显,在弓形回波的弓形顶点经过的浙江北部的嘉兴到上海青浦、宝山等一线出现了长距离的直线大风。分析表明,在整层湿度较大的环境中,来自对流系统南侧的中高层干暖气流卷人,加强了雷暴中降水的蒸发冷却作用,导致雷暴中的下沉运动明显增强,是产生长距离直线大风的关键环境因素;弓形回波系统后侧维持向前、向下倾斜的后侧人流急流,与雷暴内的下沉运动共同作用增强了风暴前侧的气压梯度,是产生此次弓形回波大风的主要原因;强低空环境风垂直切变阻止了冷池快速离开风暴主体,弓形回波前侧的阵风锋与低层环境风垂直切变形成的匹配涡对使得前侧新生对流垂直发展,是该弓形回波系统发展、维持的关键机制。A nocturnal bow echo under the warm and moist environment in front of the upper trough caused short-term severe rainfall and gust on 13-14 July 2012 is analyzed and simulated using a mesoscale model.The bow echo with high precipitation efficiency merged from two thunderstorms of multiple cells in the high humidity and strong low-level vertical wind shear envi-ronment.The long distance gust appeared along the bow echo’s path from Jiaxing to Qingpu and Baoshan,Shanghai.The mid-level entrainment of dry and warm air which came from the southern subtropical high was the critical environmental element that strengthened downdraft through evaporation and cooling.The maintained sloping-downward rear inflow jets （RIJ）in the rear part of bow echo together with the downdraft strengthed the pressure gradient of the leading edge of the bow echo,which were the critical causes of the strong gust of the bow echo.Two mechanisms for the bow echo’s develpoment and maintenance are found：the strong low level environmental wind shear prevented the cold pool from leaving the bow echo;and a vortex pair caused by strong outflow （gust front）and strong environmental vertical wind shear made the new convection develop vertically at the leading edge of the bow echo.

关 键 词：弓形回波 阵风锋 冷池 后侧入流急流 干暖气流卷入 

分 类 号：P445[天文地球—大气科学及气象学]