近50年西安市雾日数的变化趋势及可能原因

Temporal Variation and Cause Analysis of Fog Days in Xi'an City during Last 50 Years

利用西安及其周围站点泾阳和长安的雾日数和基本的气候数据,分析了近50年3个站点雾日数的时间变化特征,在此基础上对3个站点雾日数时间变化特征尤其是长期变化趋势进行了对比分析,揭示了城市与周围台站雾日数变化的特征差异。结果表明,在20世纪80年代以后3个站点的雾日数发生了显著的年代际转折性变化,西安市的雾日数显著减少,而泾阳和长安的显著增加,这种现象在冬、秋季尤为显著;而西安在各个季节的雾日数均显著减少,这种现象产生的原因除与相对湿度减小有关外,降水的减少和气温的升高也是重要的影响因素。1990年以后西安雾日数的急剧减少主要是这个时段夜间气温升高造成的。

Based on the fog days data and other basic climate data from three stations of Xi′an, Jingyang and Chang′an, the variations of fog days was studied. By comparing the temporal variation of three stations, especially the long-term variation, the difference of fog days variation between city and its surrounding areas was discovered. The result shows that the inter-decadal variations of fog days changes notably after 1980s. In detail, the fog days of Jingyang and Chang′an both increase obviously, especially in autumn and winter. However, the fog days at Xi′an decrease obviously in all four seasons. The variations of precipitation and temperature are the reasons for the variation of fog days except relative humidity. In addition, the sharp decrease of fog days is affected by the increase of nighttime temperature after 1990.