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北京721特大暴雨极端性分析及思考(一)观测分析及思考 预览 被引量:142

Analysis and Thinking on the Extremes of the 21 July 2012 Torrential Rain in Beijing Part Ⅰ: Observation and Thinking
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摘要 本文利用多种常规和非常规观测资料对北京2012年7月21日大暴雨过程的降水特点,引发特大暴雨的中尺度对流系统的环境场条件及其发生发展过程进行了全面的分析。观测分析发现:这次特大暴雨是一次极端性降水过程,具有持续时间长、雨量大、范围广的特点。降水过程由暖区降水和锋面降水组成。暖区降水开始时间早,强降水中心较为分散,持续时间长。锋面降水阶段,多个强降水中心相连,形成雨带,雨强大,降水效率高,持续时间较短。引发此次特大暴雨的中尺度对流系统的环境场条件分析发现:极端降水过程发生在高层辐散、中低层低涡切变和地面辐合线等高低空系统耦合的背景下。来源于热带和副热带的暖湿空气在暴雨区辐合,持续输送充沛的水汽,具有极高的整层可降水量、强低层水汽辐合等极端水汽条件。在充沛的水汽条件下,低涡切变、低空急流上的风速脉动、地面辐合线、地形作用等触发了强降水。随着锋面系统东移,在冷空气和适度的垂直风切变作用下对流系统组织化发展,产生较强的锋面降水。中尺度对流系统发生发展过程分析发现:降水过程首先以层状云降水和分散的对流性降水为主。随着干冷空气的侵入逐渐转化为高度组织化的对流性降水,多个中小尺度对流云团组织化发展并形成MCC,产生极端强降水。由于回波长轴方向、地形以及回波移动方向三者平行,此次过程的雷达回波具有明显的“列车效应”;并具有明显的后向传播特征和低质心的热带降水回波特点。通过此次罕见暴雨事件观测资料的综合分析,提出了需要进一步研究的问题:此次特大暴雨过程极端性降水特点及极端水汽条件的成因;北方地区暖区暴雨的形成机制;列车效应和后向传播的形成机制;对流单体的组织维持机制以及数值� Precipitation characteristics, environment conditions, generation and development of the mesoscale convective system that brought about the extreme torrential rain in Beijing on 21 July 2012 were an- alyzed comprehensively in this paper by using various conventional and unconventional data. The results showed that the extreme torrential rain had the characteristics of long duration, great rainfall and wide coverage area and its process consisted of warm area precipitation and frontal precipitation. The warm area rainfall started earlier, the severe precipitation center was scattered and lasted long while the frontal rainfall process contained several severe rainfall centers with high precipitation efficiency, lasting a short time. Environment conditions of the mesoscale convective system that triggered this extreme severe rainfall were analyzed. The results showed that interactions of high-level divergence, the wind shear and convergence with the vortex in the lower troposphere and the surface wind convergence line provided favorable environment to the severe extreme rain. The warm humid airs from the tropical and sub-tropical zones converged over the torrential rain region, continuous and sufficient water vapor manifested as high atmospheric column of precipitable water and strong low-level water vapor convergence and other extreme vapor conditions for the torrential rain. In addition, the shear, wind disturbance on low-level jet, surface intense precipitation was triggered by the vortex wind wind convergence line and the effect of terrain under the condition of the plentiful water vapour and maintained. rainfall was brought by the development and evolution suitable vertical wind shear. With the cold front moved eastward, heavy frontal of convective system made by the cold air and the Generation and development processes of the mesoscale convective system were also studied. The findings suggested that stratiform cloud precipitation and dispersed convective precipitation occurred firstly in the precipitation pro
作者 谌芸 孙军 徐珺 杨舒楠 宗志平 陈涛 方翀 盛杰 CHEN Yun, SUN Jun, XU Jun, YANG Shunan ,ZONG Zhiping, CHEN Tao ,FANG Chong ,SHENG Jie (National Meteorological Centre, Beijing 10081)
机构地区 国家气象中心
出处 《气象》 CSCD 北大核心 2012年第10期1255-1266,共12页 Meteorological Monthly
基金 国家自然科学基金面上项目(41175048)和公益性行业(气象)科研专项(GYHY201206004、GYHY201006005和GYHY20090600I)共同资助 致谢:感谢国家卫星气象中心王新、任素玲在卫星云图分析上提供的帮助,感谢国家气象中心的朱文剑,南京大家的何静在雷达资料的处理上提供的帮助.
关键词 极端暴雨 暖区降水 对流云团组织化 MCC 列车效应 extreme torrential rain warm area precipitation systematization of convective cloud clusters mesoscale convective complex (MCC) train effect
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