2011年隆冬北京初雪成因分析  

An Analysis of Dynamic Characteristics of the First Snow in Winter 2011 in Beijing

作　　者：董林 符娇兰 宗志平 

机构地区：[1]国家气象中心,北京100081

出　　处：《气象》2012年第8期913-920,共8页Meteorological Monthly

基　　金：中国气象局2011年预报员专项(CMAYBY2011057)项目;公益性行业(气象)科研专项(GYHY200906001;GYHY201006010-2);国家自然科学基金青年科学基金项目(41105030)共同资助

摘　　要：利用常规、加密观测自动站资料、雷达风廓线资料、L波段探空风、微波辐射计资料和NCEP1°×1°再分析资料,对2011年2月9—10日北京首场降雪天气过程进行了成因分析,结果表明:此次降雪过程是在高空短波槽、东风回流和地面倒槽的共同作用下产生的。东路冷空气经东北平原南下到渤海,而后向西移动形成回流。华北地区的东风回流具有西北方向浅薄、东南方向深厚的楔形结构,同时具有湿冷的特性。东风回流前沿有辐合上升气流和锋生,在近地面层形成冷垫和小幅度增湿,西南暖湿气流在冷垫上爬升造成降雪。500 hPa短波槽前的正涡度平流和850 hPa的温度平流促进了河套附近地面倒槽的发展和东移,倒槽的辐合上升区与东风前沿的辐合区叠加导致上升运动加强为北京降雪提供了动力条件。西南暖湿气流是降雪过程的主要水汽来源。In this paper, an analysis is performed on the snow weather process taking place in Beijing on February 9 and 10, 2011. The NCEP final operational global analysis data as well as the observation data, both conventional and densely AWS data, are used in the analysis. It is shown in the analytical results that this snow process is a combined consequence of the eastward returning current and the surface inverted trough. The eastward returning current is characterized by its wedge structure of being shallow in north- west direction and deep in southeast direction, as well as being wet and cold. Although there is convergent ascending current and frontogenesis, the eastward returning current is not the primary dynamic mechanism of the snowfall. Instead, it plays the role as a cooling and wetting cushion. There are three primary dy- namic mechanisms. First, a positive vorticity advection in front of 500 hPa short wave trough and a tem- perature advection at 850 hPa facilitate the development and eastward movement of surface inverted trough near Hetao. Second, the southwest current at east side of inverted trough ascends on the cooling cushion. Third, the overlay of convergent rising regions at the inverted trough and the front of east wind makes as- cending motion strong. Finally, southwest warm and wet currents serve as the main water vapor source for the snow process.

关 键 词：北京初雪 东风回流 地面倒槽 水汽 

分 类 号：P458.121[天文地球—大气科学及气象学]