具有“双对流云线”特征的北京局地暴雨初步分析  

ANALYSIS OF A LOCAL RAIN STORM IN BEIJING ASSOCIATED WITH TWO CONVECTIVE LINES

作　　者：张文龙[1] 王迎春[1] 崔晓鹏[2] 陈明轩[1] 

机构地区：[1]中国气象局北京城市气象研究所,北京100089 [2]中国科学院大气物理研究所,北京100029

出　　处：《热带气象学报》2012年第6期873-887,共15页Journal of Tropical Meteorology

基　　金：国家自然科学基金(41075047);"十一五"国家科技支撑重点项目(2008BAC37B01);中央公益性科研院所科研业务费专项(IUMKY201002)共同资助

摘　　要：2009年7月13日北京出现了一次罕见的有双"对流云线"现象的局地暴雨,对此记载并主要采用雷达资料四维变分同化系统(VDRAS)得到的分析场资料进行了初步分析,结果表明:在高空槽、低层风场辐合的有利天气尺度背景下,在北京西南部与河北交界处,由于地形作用首先出现数个对流单体;同时由于北京城区南部存在伴随中尺度风场辐合的温度梯度带,为单条对流云线的形成提供了重要条件,因而出现了对流单体呈东东北-西西南走向线状排列的形态,单条对流云线形成。在出现单条对流云线后,强降水开始发生,对流云线两侧由于强降水产生的边界层冷池出流与环境场风场形成辐合,其中南侧出流与环境场的偏南风产生狭长辐合线,北侧出流与附近雷暴冷池及雷暴高压产生的西北气流产生辐合,同时这两条辐合线阻挡削弱了环境场对原对流云线的能量和水汽输送,从而原对流云线减弱消失,在其两侧新生出两条新的对流云线。在对流云线两侧冷池出流附近,如果环境场存在较强的温度梯度、湿度梯度以及风场辐合,则可以激发出走向与环境风场垂直相交的两条平行分布的对流云线。伴随较强垂直上升速度的边界层辐合线对对流风暴的新生有显著的动力学指示意义,时效约30～60 min。A local heavy rain storm which occurred on 13 July 2009 in Beijing and exhibited two peculiar convective cloud lines is studied. The mechanism is also investigated using a four-dimensional variational Doppler radar analysis system. It is shown that in the large scale background with upper-level trough and lower-level wind convergence, several convective cells occurred firstly, which was triggered by a topographic convergence line on the border between Hebei province and the southwest area of Beijing. Meanwhile a zone of horizontal temperature gradient with wind convergence built up the initiation and evolution needed by a convective storm, and a straight line of cumulus oriented approximately in an east-northeast to west-southeast direction was observed. The rainfall rate became the largest after the formation of the cloud line, and the convective outflow due to the heavy rain collided with the ambient wind field and produced two new convergence lines. Then the two convergence lines cut off the transportation of energy and moisture to the old cloud line, replacing it with two new convective cloud lines. On the two sides of the convective line, the two new convective cloud lines parallel to the old line and perpendicular to the ambient wind are produced. The boundary layer convergence lines with intense convective advection indicate the initiation of new convective storm 30-60 minutes ahead of the observation. When there is weaker convective advection and large cold pool in the boundary layer in Beijing, the local rain storm decays quickly.

关 键 词：动力气象学 局地暴雨 雷达资料同化反演 对流云线 边界层辐合线 

分 类 号：P433[天文地球—大气科学及气象学]