中文摘要：

利用AERONET北京站2009—2011年气溶胶地基反演资料,分析了该地区气溶胶光学特性的季节变化特征.结果表明,不同季节大气气溶胶光学厚度（AOT）、Angstrom波长指数（α）具有不同的日变化规律,AOT的变化受当地气溶胶人为排放、大气稳定度条件、大气辐射等因素的影响较大,因太阳辐射的影响,α在午后存在高值或有略微增加的趋势.AOT具有明显的季节变化特征,主要表现为春、夏季大,秋、冬季小,与北京地区温带季风气候特点有关.AOT年均值为0.63.α在四季中均表现为单峰型结构,春季受沙尘粒子不连续性导入的影响,α概率分布最宽,值最小,标准差最大,α〈0.5的概率超过10%,粗粒子在四季中占比最多.夏、秋两个季节α均值〉1.1,属于典型的城市-工业气溶胶粒子.4个季节α值均大于0.9,年均值为1.07,表明北京地区以气溶胶细粒子为主.水汽柱含量具有明显的季节变化,与降水量具有相同的变化规律,夏季最多达2.33 cm,冬季最少仅有0.3 cm,春、秋季次之.

英文摘要：

Using on the ground-based aerosol retrieval data of AERONET from 2009 to 2011,the seasonal properties of aerosol optical properties in Beijing were analyzed. Our study indicates that the aerosol optical thickness（ AOT） and Angstrom exponent（ α） had quite different daily variations in different seasons. Daily average AOT is mainly affected by local aerosol emission,atmospheric stability condition as well as solar radiation. α had a maximum value or exhibited a slight increasing trend after mid-day. The AOT showed significant seasonal variation,and increased in spring and summer while declined in autumn and winter with an annual average of 0.63. The seasonal variations are related to the typical characteristics of the monsoonal climate in Beijing. The α displayed a single peak in all seasons. Because of the discontinuous emission of dust aerosol in spring,α had widest probability distribution with maximum standard deviation and minimum value. The probability of α〉0.5 exceeded 10%,which indicates that coarse particles accounted for the largest fraction during thewhole year. α became greater than 1. 1 in summer and autumn,due to the typical urban-industrial aerosols during these two seasons. Furthermore,both seasonal average（ greater than 0.9） and annual average（ 1.07） of α indicate that aerosols in Beijing are dominated by fine particles throughout the whole year. Column content of water vapor showed clear seasonal variation,which is the same as that of the precipitation. It increased to a maximum value of 2. 33 cm in summer and decreased to a minimum value of 0.30 cm in winter,the values of spring and autumn varied between the two.