乌鲁木齐城区冬季雾的分布特征及其影响因素

Distribution Characteristics and Its Influence Factors of Fog in Winter in Urumqi City

基于乌鲁木齐站(城南)和米东站(城北)2016—2020年冬季(11月—次年2月)的雾、雾日最小能见度、逐时能见度和月平均风速、月平均静风频次、月平均相对湿度等资料,利用统计学方法,分析乌鲁木齐城区冬季雾的分布特征,探讨城南和城北雾分布差异的主要影响因素。结果显示:近5 a冬季城南平均雾日44.6 d,少于城北的54.2 d,两地均为1月最多、11月最少;雾日平均最小能见度城南和城北分别为335、390 m,城南雾总体强于城北;城南雾高发于17—19时,常在11和05时消散;城北雾主要在09时和20—22时开始,大都在14时前后结束;城南和城北的雾均以持续24 h以内为主,分别占比93.5%和86.3%,其中持续3 h内的雾分别占37.2%和33.3%,城北的雾持续时间总体长于城南。风速较小、静风较多、相对湿度较大和地理环境是城北冬季雾多于城南的主要影响因素。

Based on the data of fog,foggy day’s minimum visibility,hourly visibility and monthly average wind speed,monthly average calm wind frequency,monthly average relative humidity during 2016-2020 winter of Urumqi station(south of the city)and Midong station(north of the city),distribution characteristics and its mainly influence factors of fog in winter in Urumqi city were analyzed and investigated by using statistical method.It shows that,4.6 foggy days of southern city are fewer than 54.2 foggy days of northern city during 2016-2020 winter,and foggy days reaches its maximum in January and minimum in November;average minimum visibility in foggy days is 335 m in southern Urumqi and 390 m in northern Urumqi respectively,with the fog generally stronger in the former than that in the latter.The fog of the southern city mainly begins during 17:00-19:00,and dissipates during 11:00-05:00;The fog of northern Urumqi mainly begins around 09:00 and during 20:00-22:00,while dissipates during 11:00-14:00;The fog duration are mainly 24 h,accounted for 93.5%and 86.3%respectively,while 37.2%and 33.3%for those fogs with duration below within 3 h,with the duration generally longer in northern Urumqi than that in the southern regions;The winter fog in northern Urumqi is more frequent than that in southern Urumqi,with a smaller wind speed,more calm wind frequency,larger relative humidity and special geographical conditions as its dominant causes.