2007年初一次雪后大雾天气过程分析

大雾天气是主要的灾害性天气之一。利用多种观测资料和NCEP再分析资料,分析了2007年1月15日华北和黄淮地区的雪后大雾天气产生的天气背景及其形成的温湿条件和层结特征。结果表明:在这次大雾天气发生时,亚欧大陆中高纬度的环流形势为两槽一脊型,中纬度无明显冷空气活动,南支气流较为平直,天气形势比较稳定。华北和黄淮地区位于入海高压的后部,近地面层有弱的东北风或偏东风,即有利于海洋上暖湿气流的平流输送,又不至于破坏大雾形成的温湿条件。同时,大气层结是绝对稳定的,低层有深厚的逆温层,当暖湿空气平流到温度较低的下垫面上时冷却而形成雾,因而这次大雾天气属于典型的平流雾。这种形势的稳定维持,造成了这次持续时间较长的大范围的大雾天气。另外,华北和黄淮较低的海拔高度,有利于暖湿空气的平流进入,也是大雾形成的重要因子。

A Study on a Heavy Fog Process after Snowfall in the Beginning of 2007

Heavy fog is one of the main disaster weather.From January 1 to 5,2007,a heavy fog formed over north China plain.Multiple-data was used to analyses the weather background,including temperature and humidity condition and the stratification of atmosphere.The results showed that during the days of heavy fog,the synoptic situation was stable.There was no cold air outburst.The circulation situation of the middle and high levels in Asia and Europe was one ridge two troughs circulation pattern,and the south branch air flow was straight.North China plain was situated at the rear of high pressure moving to the sea and there was weak wind blowing from northeast or east.The weak wind was not only favorable to the advection transfer of the moist and warm air,but also didn't destroy the formation conditions of heavy fog.At the same time,the stratification of atmosphere was absolutely stable and there was a deep inversion layer.When the moist and warm air advected onto this cold ground,they was cooling down and forming heavy fog.So this fog belonged to advection cooling fog.The heavy fog lasted 5 days because of the maintenance of the stable synoptic situation and the air advection.In addition,the low sea level elevation of North China plain was another important reason of the formation of heavy fog because it was favorable to the advection.