2014年5月8—9日引发珠江口区域强降水的两个长生命史MCS特征分析  

Analysis of Two Successive Rainstorm-Induced Long-Lived Mesoscale Convective Systems Struck Pearl River Estuary During 8—9 May 2014

作　　者：陈涛 张芳华 符娇兰 于超 CHEN Tao;ZHANG Fanghua;FU Jiaolan;YU Chao(National Meteorological Centre,Beijing 100081)

机构地区：[1]国家气象中心,北京100081

出　　处：《气象》2020年第4期449-461,共13页Meteorological Monthly

基　　金：国家重点研发计划(2017YFC1502103);中国气象局暴雨专家创新团队专项(CMACXTD002-3)共同资助。

摘　　要：2014年5月8日上午至9日白天,广东中南部珠江口地区连续受MCS-A1、MCS-A2两个长生命史中尺度对流系统影响,形成长时间强降水。其中5月8日午后华南内陆地区MCS-A1逐步增强,从广西东部向广东珠江口方向移动,陆上活动时间超过11h;MCS-A2从9日凌晨至上午持续影响珠江口沿海地区,维持时间超过9 h,导致珠江口沿海地区出现400 mm以上单站降水量。过程发生前,8日早上华南南部地区具有弱地面温度梯度,中午MCS-A1对流触发与广西南部地面南风增强、华南南部云开大山—云雾山中尺度地形抬升有紧密关系;在弱斜压环境条件下,MCS-A1从层云伴随线状对流结构演变为中尺度涡旋组织结构。8日夜间MCS-S1入海后,与陆上遗留冷池相关的地面温度边界稳定在珠江口西侧沿海地区;9日凌晨西南低空急流增强后,MCS-A2在珠江口沿海残留冷池边界附近开始发展,在向上游迎风方向传播的过程中,逐步形成多条平行β中尺度线状对流组织结构,对流系统整体移动缓慢,造成珠江口沿海地区出现较高的总降水量。计算表明MCS-A2冷池边界扩张速度与低层垂直切变相对平衡,有利于形成较为直立的对流单体,增强的边界层水汽输送、更高的对流单体高度有利于产生较高的降水强度。通过总结这两个华南地区长生命史MCS发生发展过程,表明通过分析对流反馈造成的边界层/近地面层热动力特征变化,对于分析MCS发展特征、提高华南前汛期中尺度暴雨预报能力具有重要意义。Two successive long-lived mesoscale convective systems(MCS-A1,MCS-A2)struck Pearl River Estuary of South China during 8—9 May 2014,and induced extreme precipitation over the region.From noon of 8 May MCS-Al sustained over than 11 h on land of South China,with slowly moving towards southeast from east of Guangxi to Pearl River Estuary in Guangdong.The successive MCS-A2 sustained more than 9 h,inducing rainfall of more than 400 mm along the coast of the Pearl River Estuary from early morning to noon of 9 May.Weak cold surface layer sustained in the south of South China with weak surface temperature gradience on the morning of 8 May before the convection burst.The initialization of convection was connected with strengthening of surface south wind and topographic lifting near noon of 8 May.MCS-Al evolved from training line/adjoining stratiform(TL/AS)to mesoscale vortex in convective organization under weak baroclinic environment.With propagation of surface cool pool due to MCS-A1’s precipitation in the early night of 8 May,surface temperature boundary and wind convergence zone was pushed to the southwest coast of Guangdong.In the late night of 8 May MCS-Al moved out of land,then MCS-A2 was developing adjointly to the remnant cool pool boundary induced by MCS-Al with low-level southwest wind enhancing in the early morning of 9 May.MCS-A2 was composed by multiple parallel meso-βscale line-type convective systems,the extreme rainfall was related with quasi-stationary cool pool boundary,train-moving cells in meso-βscale line-type convective systems with high precipitation efficiency.From late night of 8 May to morning of 9 May,the balance between cool pool outflow and low-level vertical shear could sustain upright convective cells of MCS-A2.In conclusion,with carefully researching on convective feedback to boundary and surface layer,the forecast skills could be improved for heavy rainfall events in weak synoptic-forcing environment during the pre-rainy season in South China.

关 键 词：华南前汛期 中尺度对流系统 暴雨 冷池 线状对流 

分 类 号：P458[天文地球—大气科学及气象学]