中文摘要：

利用PWD22能见度仪监测数据，分析了上海市2008年-2009年能见度日变化规律和四季逐日变化特征，以及能见度和混合层高度（MLH，MixedLayerHeight）、空气污染指数（API）及气象要素（相对湿度、风速、温度）的相关性。结果表明，能见度一峰一谷日变化特征明显，峰值出现在14：00～16：00，谷值出现在6：00～8：00。能见度与MLH相关性显著，与温度最差。能见度和气溶胶光学厚度（AOT）线性拟合呈负相关关系，且夏季相关性最显著，冬季最差。

英文摘要：

Using visibility data from Vaisala Present Weather Detector （ PWD22）, diurnal and seasonal var- iation of visibility in Shanghai were analyzed, as well as relationship between visibility and MLH, API and major meteorological factors such as relative humidity, wind speed and temperature. Results indicated that diurnal vari- ation of visibility was obvious, which showing a peak from 14：00 to 16：00 and a valley from 6：00 to 8：00. There was significant correlation between visibility and MLH and the worst with temperature. It showed a negative correlation between visibility and aerosol optical thickness （AOT） by correlation analysis and linear fitting, which is the most significant in summer and the worst in winter.