2004-11-28～12-04华北等地大雾天气的中尺度分析

Mesoscale Analysis on the Heavy Fog Occurred in the Area of Northern China from Nov.28th to Dec.4th in 2004

对2004年11月28日～12月4日发生在华北及黄河中下游地区的持续性大霉天气进行了中尺度分析，结果发现，地面中尺度辐合线（区）与辐射降温有利干形成辐射雾。此次大雾在持续过程中性质发生了改变，由辐射雾转变为平流雾。若东北地区的地面冷高压中心西侧或南侧另有一小高压环流，通常为一种有利于华北及中东部地区产生或维持大雾天气的环流型，在其南侧及西南侧产生的准地转流和非地转流在华北及黄河中下游地区的交汇为该地区带来了丰沛的水汽。

We analyze the durative heavy fog occurred in northern China and middle and lower region of Huanghe River from Nov. 28th to Dec. 4th in 2004 by using mesoscale system, the result shows that the ground mesoscale convergence line and the radiation detemperature make for the forming of radiation fog, The character of the fog changes during its sustaining, and changes radiation fog into advection fog. If there is a subsidiary high pressure circulation to the west or to the south of the center of the ground cool high pressure which lies in the area of the northeastern part of China, then it usually is a circulation type which is profitable for the forming and sustaining of heavy fog in the area of northern, middle and eastern part of China. The quasi - geostrophic flow and non - geostrophic flow which are produced in the south and southwest part of the high pressure encounter each other in the previous areas and brine plenty of water vapor to those places.