中文摘要：

利用气象要素和气溶胶观测资料,分析了西安市2013年12月17～25日、2014年2月20～26日两次雾霾过程的气象要素风、温、湿变化,气溶胶质量浓度、粒子谱分布及散射系数的变化及其在雾霾天气的形成、发展、维持与变化中的作用.结果表明：APS观测的粒子谱变化表明,雾霾过程中,粒径在0.5～0.835μm之间的粒子的数浓度增加最明显,雾霾后,〈2μm和〉3.5μm粒子的数浓度下降显著;SMPS观测的粒子谱变化表明,霾过程中细粒子的数浓度主要集中在30～300nm,且具有明显的日变化特征,08：00～14：00、18：00～02：00为数浓度的大值时段,细粒子段污染物浓度的增加主要是由粒径大于140nm以上的粒子引起的.散射系数的增加与粒径小于1.0？m粒子的数浓度增加有关,也是雾霾期间能见度恶化的重要原因之一。

英文摘要：

Based on the meteorological and aerosol observed data, the change of wind, temperature ,humidity, aerosol mass concentration, particle size distribution and scatter coefficient had been analyzed in Xi＇an on 17～25 December 2013 and 20-26 February 2014. These factors had an effect on the fog/Haze of formation, development and lasting. The results showed： By ASP observation, particle number concentration between 0.5μm and 0.835μm of aerodynamic diameter increased obviously during the formation and maintaining of fog/haze. After the process of fog/haze, the particle number concentration of aerodynamic diameter 〈2.0μn and 〉3.5μm decreased significantly. By SMPS observation, particle number concentration was mainly concentrated in 30nm-300nm of aerodynamic diameter and had obvious diurnal variation during the formation and maintaining of fog/haze, the time of large particle number concentration appeared from 8a.m. to 2p.m and from 6p.m to 2a.m. The increase of pollutant concentration was mainly related to the increase of number concentration of aerodynamic diameter〉140nm.The increase of scatter coefficient was related to the increase of number concentration of aerodynamic diameter〈l.0pm. This was one of the important factors which caused the visibility deterioration.