北京连续降雪过程分析  

PRIMARY ANALYSIS OF THE LONGEST-LASTING SNOWFALL IN BEIJING

作　　者：王迎春[1] 钱婷婷[2] 郑永光[2] 

机构地区：[1]北京城市气象研究所,北京100089 [2]北京大学物理学院大气科学系,暴雨监测和预测实验室,北京100871

出　　处：《应用气象学报》2004年第1期58-65,共8页Journal of Applied Meteorological Science

基　　金：北京市科学技术委员会项目H0 2 0 62 0 1 90 0 91;国家自然科学基金重点项目 40 2 3 3 0 3 6的资助

摘　　要：该文对 2 0 0 2年 1 2月份北京出现的 1 841年以来历史上最长的连续 6天的降雪天气进行了合成分析和诊断分析。北半球合成环流形势显示 ,连续降雪发生在东亚稳定的纬向环流形势下 ,其上游地区强大经向环流和阻塞高压使中纬度东亚和西太平洋纬向环流得以维持。东亚合成环流的垂直结构表明 ,连续降雪期间华北地区始终处于锋区中 ,并存在低空辐合、高空辐散的散度场垂直分布结构。卫星水汽云图显示出有水汽通道向河套倒槽云系输送水汽。华北地区的诊断分析表明 ,地面和边界层中山东地区分裂高压南侧向北回流的偏南气流是造成降雪的主要水汽通道。变形场的流场结构使水汽在北京附近辐合。垂直剖面展现了华北回流降雪天气近地面层的浅薄的冷空气垫 ,和暖湿空气回流在冷空气垫上的爬升 。Five-day snowfall , which occurred in Beijing on 19-23 December 2002 and became the longest-lasting snowfall since 1841, is compositely analyzed. Five-day composite circumfluence showed that the snowfall took place in the constant zonal circulation. During the period, there was a strong Mongolia High on the surface. And the ridge of high pressure protruded southward our country's east. On 850 hPa, Hetao area has a northward trough, and Beijing lied in the positive vortex of the trough. On 500 hPa, a front crossing Asia from west to east located 40～45°N. On 300 hPa, Beijing situated positive vortex of the axis of the jet, which was straightly zonal. The vertical section indicated that Beijing was convergent on the low-level whereas divergent on the high-level. And there were two fronts. In a conclusion, Beijing was controlled by the large-scale circumfluence that was in favor of snowfall. The analysis of Huabei area during the continuous snowfall showed that the deformation field locating the north of the trough had evident vapor convergence. Moisture flux indicated that vapor came from the return flow of the Yellow Sea, but not the return flow of Bo Sea. The warm advection in the east of Hetao trough was the cause of ascending.

关 键 词：降雪过程分析 诊断 回流 北京 

分 类 号：P426.63[天文地球—大气科学及气象学]