贵阳机场两次辐射雾过程对比分析

Comparative Analysis of Two Radiation Fog Processes at Guiyang Airport

摘要: 利用机场地面观测数据和ECMWF ERA5再分析资料等，对贵阳龙洞堡机场2019年12月6日(过程1)和2022年1月18日(过程2)的辐射冻雾过程，从气象要素时间演变、环流特征和水汽、热力及层结方面进行对比分析，结果表明：两次过程均为典型的雨后回暖天气下由于辐射降温形成的浓雾，处于高空暖脊、地面弱气压场的形势下，生成于晴夜、微风、辐射降温最强烈的凌晨，前期弱降水为近地面提供大量水汽。在静稳大气环境下，辐射雾出现越早、造成的能见度越低，雾维持时间越长，两次过程最低值均出现在2日08:00~10:30。过程1受雨后冷空气南下和午后多云水汽蒸发影响，近地面层水汽含量低于过程2，但雾维持阶段雾滴含量过程1仅比过程2略低。近地面层逆温越强、气温下降越快、雾滴越浓和微风且有一定上升运动有利于浓雾的发展和维持。两次过程湿度均未达到100%，雾维持阶段温度露点差保持在0.5℃~0.6℃，能见度均具有爆发性增强和消散耗时极短的特点。浓雾形成前两次过程气温下降根据速度均可分为3个阶段，其中第一阶段降幅较慢，第二阶段两次过程每小时均降低0.9℃，第二和第三阶段间有气温小幅反弹。浓雾消散阶段，气温呈直线上升。两次过程雾滴含量达到0.39 g/m³时能见度降至800 m，降至0 g/m³时，能见度快速升至3000 m以上。

Abstract: Based on the airport ground observation data and ECMWF ERA5 reanalysis data, the radiation freezing fog processes of Guiyang Longdongbao airport on December 6, 2019 (process 1) and Janu-ary 18, 2022 (process 2) are compared and analyzed from the aspects of time evolution of meteoro-logical elements, circulation characteristics, water vapor, heat and stratification. The results show that the two processes are the thick fog formed by radiation cooling in typical warm weather after rain, which is located in the upper warm ridge under the situation of weak air pressure field on the ground, it is generated in the early morning of sunny night, breeze and radiation cooling. The weak precipitation in the early stage provides a large amount of water vapor near the ground. In the static atmospheric environment, the earlier the radiation fog appears, the lower the visibility, and the longer the fog lasts. The lowest values of the two processes appear at 08:00~10:30 on the 2nd. Process 1 is affected by the southward movement of cold air after rain and the evaporation of cloudy water vapor in the afternoon. The water vapor content in the near surface layer is lower than that in process 2, but the droplet content in process 1 is only slightly lower than that in process 2 in the fog maintenance stage. The stronger the inversion in the near surface layer, the faster the temperature drops, the thicker the fog droplets and the breeze, and there is a certain upward movement, which is conducive to the development and maintenance of dense fog. The humidity in both processes did not reach 100%, and the temperature dew point difference in the fog maintenance stage was maintained at 0.5˚C ~0.6˚C. The visibility had the characteristics of explosive enhancement and very short dissipation time. The temperature drop in the two processes before the formation of dense fog can be divided into three stages according to the speed. The decline in the first stage is slow, and the two processes in the second stage are reduced by 0.9˚C per hour. There is a slight rebound in temperature between the second and third stages. In the fog dissipation stage, the temperature rises in a straight line. In both processes, when the droplet content reaches 0.39 g/m³, the visibility decreases to 800 m, and when it decreases to 0 g/m³, the visibility quickly rises to more than 3000 m.