冬季乌鲁木齐城区和机场雾的特征及地面气象条件对比分析

Characteristics of Urban and Airport Fog in Winter and Analysis of Ground Meteorological Conditions in Urumqi

基于乌鲁木齐城区气象站和城北乌鲁木齐地窝堡国际机场(简称机场)2016—2021年冬季逐小时地面气象观测资料,对近6年冬季两地雾的特征及其对应的地面气象条件进行对比分析。结果表明:城区和机场3种情景雾日出现的概率较为接近,但是不同级别雾日的出现概率有一定的差别,其中大雾日数以两地同时出现为主,概率最高达到19.6%。两地不同强度雾日数和雾过程的频次均呈明显下降趋势,其中机场大雾日数和过程频次均略多于城区。城区雾起始时间有33.3%集中在01—04时,而机场有25.2%出现在08—10时。城区雾强度总体强于机场雾,机场雾日最小能见度均值(412.9 m)高于城区(360.8 m)。此外,在冬季准噶尔盆地的“冷湖效应”和山谷风的共同作用下,机场一带盛行的西北偏北和偏北风导致温度相对较低,有利于降温形成大雾天气,城区和机场温度分别在-12~-4℃和-16~-8℃时出现大雾的频率最高,比例分别高达57.4%和50.1%。

Based on the hourly meteorological observation data from the urban area and airport of Urumqi in winter from 2016 to 2021,the characteristics of fog and the ground meteorological conditions are analyzed in detail.It shows that,the probability of occurrence of three scenarios of fog days in winter is relatively close,but there are certain differences in the probability of occurrence of fog days of different levels.Among them,the number of heavy fog days is mainly“two places appear at the same time” scenario,with the highest probability of occurrence reaching up to 19.6 %.Furthermore,the number of fog days and processes with different grades in the urban area and airport of Urumqi exhibits significant decreasing trend.Specifically,the number of heavy fog days and processes in the airport is slightly more than those in the urban area.In view of the initial time of fog,the accumulated occurrence frequency reaches up to its mamimum 33.3 % in 01:00-04:00 BJT in the urban area,and the maximum frequency in the airport is around 25.2 % in 08:00-10:00 BJT.In addition,the intensity of fog process is stronger in the urban area,the mean value of minimum visibility in foggy days in the airport is412.9 m,which is higher than that in urban areas(360.8 m).Due to the combined effect of the“ cold lake effect ”and valley wind in the Junggar Basin in winter,The predominant north-northwest and northerly winds near the airport cause a very low temperature,which is favorable for the production of severe fog.The maximum occurrence of fog in the urban area and the airport are 57.4 % and 50.1 % with temperature range of-12 to 4 ℃ and-16 to 8 ℃,respectively.