40年来新疆雾的演变特征及大雾天气过程分析

Change Characteristic of Fog and Analysis on Weather Process of Heavy Fog in Xinjiang in Nearly 40 Years

利用新疆90个气象站43年地面观测资料,对新疆雾的天气、气候特征进行分析,结果表明:(1)雾主要出现在北疆,尤以天山山区最多;雾日的年际变化波动性大、周期性差;冬季雾日最多,多自午夜时分起,正午之前散,早上是高发时段。绝大多数的雾持续时间在3h之内。(2)对281次大雾天气过程普查后分为3种地面形势,并对成因进行了讨论。

Based on the daily surface observation data of fog at 90 meteorological stations during 1961-2003, the spatial-temporal characteristic of fog and the weather pattern and the cause of formation of 281 heavy fog processes in Xinjiang were analyzed. The results are followed. （ 1 ） Days with fog was more in Noah Xinjiang than that in South Xinjiang, more in mountainous areas than in plains, was the most in the Tianshan Mountains and the least in the Tarim Basin. Normal of days with fog was the most at Daxigou and Tianchi station, about 54 and 58 days. It was during twenty to forty days in mountainous areas and from five to ten days in plains, less than one day in South Xinjiang. In the low mountainous areas and plains, the occurrence of fog was frequent in cold season from November to April, was part of winter pattern regions, but it was all year in the high mountainous areas, more frequent during May and September, such as Daxigou station, it was only summer pattern region in Xinjiang. The daily variations of fog were very coincident, the mass of fog occurred at 00 BST and evanesced before 14 BST, more frequently from 8 to 10 BST. Most fog persisted within three hours, more within one to thirty minutes or one half to one hour. The longest persistence time was during twenty to forty hours in North Xinjiang and less than twenty hours in South Xinjiang. （2） In the 281 heavy fog weather processes, there was 70% only occurred in North Xinjiang, 28% simultaneously occurred in Noah and South Xinjiang and 2% only occurred in South Xinjiang. Heavy fog weather processes focused on November to February, most in December, more persisted one to four days. Since 1987, Heavy fog weather processes evidently decreased, it was possible that born a relation with climatic conversion from warm-dry to warm-damp in Northwestern region. It was found that heavy fog weather processes was affected by high pressure systems via investigating the history surface chart, the occurrence of heavy fog weather processes had a important relation with center situation and distribution of high pressure and intensity of cold air mass, especially it was to the less benefit of occurrence of heavy fog weather processes when cold air speedily moved eastward. There were three patterns of surface synoptic situation of heavy fog weather processes, such as zonal high pressure, eastern high pressure and South Xinjiang high pressure, gave first place to zonal and eastern high pressure. High humidity, lower temperature, low wind and inversion layer were benefit condition for occurrence of heavy fog weather processes.