华北地区一次连续大雾的诊断分析

对2004年11月29日到12月4日华北地区一次连续大雾过程进行了分析.结果表明:高空西北气流以及西南暖湿气流是大雾发生的重要条件;大雾期间地面上的相对湿度达到了94%以上,华北地区先后被稳定的大陆高压和鞍形场控制.低层充沛的水汽、稳定的层结条件以及低空风速较小导致该地区水汽不能及时随大气扩散;高层下沉以及低层有弱的上升气流在低空的某层高度上易形成稳定层结,导致大雾的形成.

Diagnostical Analysis of a Continuative Fog Event in North China

The continuative fog event lasted from 29 November to 4 December 2004 is analyzed. The results indicate that the northwestern airflow and the warm and humid airflow from southwest at upper levels are important factors of the continuative fog event; the surface relative humidity was up to 94% and North China was controlled by the stable Continental High and a saddle shaped field, so there was abundant water vapor, stable stratification, and very small wind speed at lower levels, leading to the fact that water vapor could not diffuse timely; the upper level sinking air and lower level rising air led jointly to the stable stratification, so heavy fogs occurred.