大连地区大雾天气气候特征及成因

Study on the synoptic and climate character as well as causes of fog in Dalian

利用2001-2012年大连地区大雾气象观测资料,对近十几年大连地区大雾的气候特征和天气学成因进行了分析,结果表明:大连地区大雾日数,长海最多,金州最少;除金州外,夏季最多,春季次之,冬季最少.大雾生成的日变化规律为,春季大雾多生成于02:00-08:00,20:00-23:00两个时段;夏季大雾多出现于20:00-次日08:00.大连地区产生大雾的主要天气形势可分为4种类型:高压后部型、气旋型、冷锋型、均压场型,其中除气旋型外的3种类型的大雾天气从开始到维持阶段水汽都比较充沛,盛行南到东南风,转为偏北风后大雾消散结束,而气旋型大雾天不如其他3种的水汽那么充沛,从开始到结束都为偏北风.大雾形成阶段在大连地区低空通常有暖平流输送来大量水汽,都有一个水汽聚集的过程,其层次一般都在900 h Pa层(海拔1 000 m左右)或其附近,并且该地区低空都会出现气流辐合、上升的三维流畅特征.大雾维持期间,通常风速较小,层结稳定,温度露点差也较小,接近饱和状态;当大雾消散时通常当地低空会有冷空气入侵,风速迅速增大,高空都会受到冷平流的影响.

By using the meteorological data from 2001 to 2012, the climate character and synoptic causes of fog in Dalian were analyzed and the results showed that the number of foggy days in Dalian was largest in Changhai and smallest in Jinzhou and, except Jinzhou, it was the largest in summer, then in spring, and the smallest least in winter. Diurnal variation of fog in spring occurred more during 02 ： 00-08 ： 00 and during 20 ： 00-23 ： 00, but less during other times. In summer it was more generated from 20 ： 00 to 08 ： 00 of the next day and less generated during other times. In Dalian, the foggy weather situation could be divided into four main types： 1） high-pressure rear type, 2） cyclone type, 3） a cold front type and 4） uniform pressure field type. Vapor was more abundant for types 1）, 3）, and 4）, with southeast or southerly winds from the beginning to the end, and it was not so abundant for type 2）, with northerly winds from the beginning to the end. In the formation stage, there were usually a vapor gathering process by warm advection to transport a lot of water vapor in the low levels, which were generally around 900 hPa, and there would be converging, rising three-dimensional fluid characteristics. In the maintain stage, the wind speed was usually small, of stable stratification, and the dew point temperature difference was smaller, close to saturation.When the fog dissipated, there were usually cold air intrusion from low levels, with the wind speed increasing rapidly causing a high level cold advection.