西安雾日和霾日时空特征分析

Spatial and Temporal Distribution Characteristics of Fog Days and Haze Days in Xi'an

利用1960～2012年西安区域7个气象站的历史地面观测资料,统计分析了西安地区雾日、轻雾日及霾日的时空变化特征。结果表明,1960～2012年西安区域雾日分布呈近山区多、平原区少的特点;轻雾日的分布呈城区多发、郊区少发的特征;霾日在城区为高发区,近郊次之,远郊最少。西安地区年平均雾日数呈现先增加后减少的变化特征,轻雾日数以9.0 d/10a的速率呈波动性显著增加趋势,霾日以-7.7 d/10a的速率呈波动性显著减少趋势。西安地区雾日数在年内呈单谷型分布,全年最低值出现在夏季6月(0.2 d),冬季12月出现最高值(3.8 d);轻雾日数在年内呈"V"型分布,全年轻雾日数最低值出现在6月(7.6 d),冬季12月份出现最多(17.4 d);霾日数在年内呈"U"型分布,春末(5月)～初秋(9月)霾日出现频率在年内变化曲线上表现为一个宽广的"U"型底部,在冬季1月份上升至最高值(6.1 d)。

The spatial and temporal distribution characteristics of fog/mist/haze were analyzed based on the surface observed data of seven stations in Xi'an area from 1960 to 2012.The results showed that the number of foggy day was more near the mountain,less in plain terrain.The number of misty day was more in urban area,less in suburbs.The number of hazy day was more in urban area,less in suburbs,and least in outer suburbs.The number of foggy day increased in the early stage and decreased in the late stage.The number of misty day increased(9.0 d/10a) while that of hazy day decreased(-7.7 d/10a).In a year,the variations of foggy days display a 'single valley type,which were minimum(0.2) in June and maximum(3.8) in December.The variations of misty days display a 'V' type,which were minimum(7.6) in June and maximum(17.4) in December.The variations of hazy days display a 'U' type,which were at the bottom from May to September and increased to the maximum(6.1) in January.