河南省北部一次大雾天气过程分析

利用地面观测和探空资料以及NCEP1°×1°再分析资料，分析了2007年12A25-27日河南省北部大雾的成因，结果表明：由于降水后低层相对湿度较大，大气层结稳定，地面处在均压场里，风速较小，且大气低层为弱的上升运动、中高层为强的下沉运动，有利于低层水汽聚集，使湿层达到一定的厚度，从而使垂直能见度变差，雾的浓度变大。

Analysis of Heavy Fog in Northern Henan Province

The paper analyzed the cause of a heavy fog occurred in northern Henan on December 25 -- 27, 2007 by using the surface - based observation, sounding data and the NCEP 1°× 1° reanalysis data. The results show that the reason is the larger low -level relative humidity after the rainfall as well as the stable atmospheric stratification which the surface is in the uniform pressure field and the wind velocity is relatively small. And there is a weaker ascending motion in the lower atmosphere but the middle - high has a stronger descending motion. This distribution is beneficial to the accumulation of the water vapor in the low level which lead to the wet layer reached a certain thickness so that the vertical visibility is reduced and the concentration of the fog is enhanced.