中文摘要：

观测了2009年12月至2011年11月期间上海市嘉定区的大气能见度，得到了能见度的年变化、季节变化和日变化特征。结果显示，上海市嘉定区大气能见度的年平均值呈现2011年〉2010年〉2009年的趋势；日变化均表现为6：00-8：OO能见度最差，14：00-15：00能见度最好。而2010年能见度的季节变化则不同于2009年和2011年，这有可能是受到了上海世博会举办的影响。同时，采集了2010年不同粒径的大气颗粒物样品，分析了颗粒物浓度及组分对大气能见度和消光系数的影响，结果表明，2010年粒径在0．40～1．00μm的颗粒物浓度对上海市嘉定区大气能见度的影响是最大的；在世博期间，粒径小于0．95μm的大气颗粒物对消光系数的影响最大；sO2-4、N0-3、NH＋4、有机碳（Oc）和元素碳（Ec）5种化学组分对消光系数有明显的贡献。

英文摘要：

The atmospheric visibility in Jiangding District of Shanghai was observed from December 2009 to No- vember 2011. Base on which, the yearly, seasonal and daily variation features of atmospheric visibility were studied. Results showed that the visibility was improved from 2009 to 2011, mean the annual averages of atmospheric visibility followed the order of 2011〉2010〉2009. The diurnal variation of visibility was consistent in recent years, presenting a peak value at 14：00-15：00 and a minimal value at 6： 00-8：00 in the morning. Due to the effect of World Expo in Shanghai,the seasonal variation of visibility in 2010 appeared differently from those in 2009 and 2011. The atmospher- ic particulates of different particle sizes were collected simultaneously in 2010. Meanwhile, the influences of particu- lates concentrations and chemistry components on visibility and extinction coefficients were analyzed. The result indi- cated that the particulates with diameters of 0.40-1.00 μm had a great impact on the atmospheric visibility. During the World Expo,the particulates of diameters smaller than 0. 95 μm had a better correlation with the extinction coeffi- cient,in which the chemistry components （SO2-4 ,NO- 3, N H＋4 , OC and EC） made obvious contributions.