山地机场一次平流雾天气演变特征及成因分析

Evolution Characteristics and Cause Analysis of an Advection Fog at Mountain Airport

利用贵州省仁怀市茅台机场地面观测资料和ERA5逐时再分析等资料,对2018年2月14~15日茅台机场一次大雾过程进行诊断分析。结果表明:本次大雾是一次典型平流雾天气过程,在北方“西高东低”的环流形势和南方南支槽东移的背景下发生。大雾前半段机场近地面主要受暖平流影响,后半段主要受弱冷平流影响,期间锋面过境对大雾有短暂清除作用;暖平流雾阶段,机场受来自孟加拉湾和南海水汽的影响,为平流雾的发生和维持创造了水汽条件;弱冷平流雾阶段,近地面有辐合中心,南来水汽与机场西北面赤水河谷水汽在此汇聚;大雾过程中,机场上空的逆温(或等温)层为冬季云贵准静止锋的锋区所在,它使得大气层结更加稳定,有利于大雾生成和维持;冷空气主体南下至贵州北部后,冷平流造成的低层下沉运动和水平扩散条件的改善是导致大雾最终消散的原因。

Based on the ground observation data and ERA5(0.25°×0.25°)hourly reanalysis data of Maotai Airport in Renhuai,Guizhou,the synoptic and diagnostic were used to comprehensively analyze the fog process at Maotai Airport from February 14 to 15,2018.The results show that the fog was an typical advection fog.In the first half of the fog,the near-ground of the airport was mainly affected by warm advection,and in the second half,it was mainly affected by weak cold advection.The frontal transit had a temporary clearing effect on the fog.The whole process took place under the background of the pattern of higher in the west and lower in the east and the eastward movement of the southern branch trough.In the warm advection fog stage,the airport was influenced by the water vapor from the Bay of Bengal and the South China Sea,which created the water vapor conditions for the occurrence and maintenance of advection fog.In the weak cold advection fog stage,there was a convergence center near the ground,and the water vapor from the south converged with water vapor from Chishui River Valley to the northwest of the airport.The temperature inversion(or isothermal)layer over the airport in the fog process was the front area of the quasi-stationary front of Yunnan-Guizhou in winter.It stabilized the atmosphere,making it easier for fog to form and sustain.After the main body of cold air moved south to the northern part of Guizhou,the lower level subsidence movement caused by cold advection and the improvement of horizontal diffusion conditions were the reasons for the final dissipation of the fog.