豫北一次持续性大雾的成因分析

Analysis of the Sustained Heavy Fog Process in the North of Henan Province

本文应用MICAPS探空资料（第五类站点数据）及地面观测资料（第一类格点数据、第四类站点数据）和NCEP再分析资料,对2009年11月13-14日发生在豫北地区的一次大雾天气过程的形成、持续及其性质转变的原因进行分析,发现地面中尺度辐合线（区）的时空分布与大雾过程有时间上的伴随关系。水汽通量输送和温度平流的变化以及地面辐射降温的共同作用导致了这次大雾的性质在持续过程中发生了转变,即由辐射雾变成平流雾。分析表明：13日08时之前豫北的降雪带来的充足水汽和夜间晴朗少云微风造成的辐射降温是形成辐射雾的主要原因;13日14时开始在豫北水汽通量输送加大和暖平流不断加强的同时地面持续降温,使得暖湿空气在较冷的下垫面冷却导致辐射雾转变为平流雾。

This article analyzed the mesoscale mechanism of one heavy fog process that happened on the November 13 - 142009 in the northern part of Henan province,based on the MICAPS high altitude,ground observation data and NCEP 1° × 1°re- analyzed data. The author found that the mesoscale convergence on the ground was synchronous to the formation of this heavy fog process what in the time concomitance relations. Three reasons lead to this heavy fog process had varied,which are the changed of water vapor flux,the temperature thermal advection and the surface radiation cooled. Which physically transformed radical fog into advection fog. This analysis indicate that,before 8：00 on November 13,the snowfall brought the aqueous vapor and the sunny frigid night weather condition caused the surface radiation cooling which formed the radical fog. After14：00 on November 13,the increased of the water- vapor flux,the warm advection at the same time and the ground continually decreased temperature,that caused the warm air and wet air on the frigid surface cooled down what made the radical fog physically transformed into advection fog.