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气象:2010,36(12):19-27
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北京地区一次引发强降水的中尺度对流系统的组织发展特征及成因探讨
(1.中国气象科学研究院, 北京 100081;2.北京市气象局, 北京 100089)
Investigation on Systematic Development of Mesoscale Convective Systems in a Torrential Rain Event over Beijing
(1.Chinese Academy of Meteorological Sciences, Beijing 100081;2.Beijing Meteorological Bureau, Beijing 100089)
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投稿时间:2010-04-29    修订日期:2010-06-21
中文摘要: 2008年8月10日白天到夜间,北京地区发生了全市性强降水,其中10日下午15:00—18:00经过城区的三个β中尺度对流单体不但产生强的降水(局地达到45 mm/h和12 mm/5 min的雨强),还出现了明显的组织化发展的迹象。利用北京地区多种高时空观测数据(包括地面自动站、多普勒雷达、风廓线、微波辐射计等)和雷达变分同化分析系统(VDRAS)的高分辨率分析场资料,重点分析研究了这三个对流单体组织发展的特征和成因。结果显示:(1)10日下午城区的短时暴雨与大范围降水云系前部(北京城区南部到房山东部)近地面层β中尺度切变线的产生直接相关,该切变线触发了对流,使对流单体组织化发展成为准南北向排列的β中尺度线状对流系统影响了城区;(2)降水发生前2小时左右,北京本站边界层环境风风向由西南向偏东的转变以及城区局地对流有效位能的短时快速积累,是城区对流得以发展的关键局地环境因素;(3)10日下午北京西北部山区的层状降水系统的低层(500 m以下)形成的西北冷性水平出流与北京东南部低层东南暖平流在城南一带汇合形成的风切变是导致对流单体移进北京后组织化和进一步发展的直接原因。因此,在有利的大尺度环流背景下,对于北京大范围降水而言,预报中需特别注意降水云系移动的近前方、边界层环境风风向的变化(即偏东风的出现),因为大范围降水发生后近地面层所形成的水平出流,可能与其前部偏东环境风构成明显风切变而激发对流的产生和组织化。
Abstract:There was a torrential rain occurring in Beijing during 15:00—18:00 BT 10 August 2008, and it was the afternoon of that day there were three meso β convective cells that moved to city of Beijing, generated heavy rainfall (can be 45 mm/h and 12 mm/5 min) and had an obvious organizational development. Many high spatial temporal resolution data, such as auto weather station (AWS) network data, Doppler radar data, wind profile data and variational Doppler radar analysis system (VDRAS), are used to analyze the organizational development of the mesoscale convective system in this case. It is revealed that: (1) the cause for the organizational development of three convective cells in the afternoon is about the appearance of meso β shear which was in the front of stratified precipitation system; (2) there are obvious changes before starting to rain in main urban areas of Beijing, such as accumulation of CAPE, and environmental wind whose direction changed from south to east; (3) the casue for the origanizational development of the three convective cells is due to the shear generated by the confliction between the northwest cold horizontal flow from stratified rain system and the southeast warm horizontal flow beneath 500 m. Therefore, at the advantaged large scale background, with regard to the weather forecast of large scale rain event, one of the key places is in the front of stratified precipitation system, where conflict between the cold horizontal flow and the environmental wind before the system maybe triggers the organizational development of convective system.
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基金项目:科技部《北京奥运短时临近预报实时业务系统研发》(2005BA904B05)和北京市科委《城市突发气象灾害风险防范与快速响应关键技术研究》(Z090506016609001)资助
引用文本:
孙靖,王建捷,2010.北京地区一次引发强降水的中尺度对流系统的组织发展特征及成因探讨[J].气象,36(12):19-27.
SUN Jing,WANG Jianjie,2010.Investigation on Systematic Development of Mesoscale Convective Systems in a Torrential Rain Event over Beijing[J].Meteor Mon,36(12):19-27.