利用2011～2014年北京太阳光度计数据对北京地区的气溶胶光学特性进行了研究。北京地区气溶胶光学厚度(aerosol optical depth, AOD) 全年较高,四年440 nm波长的AOD年均值分别是0.67±0.70, 0.69±0.71, 0.73±0.66, 0.75±0.66。AOD月均值表现出 一定的季节变化,最大值和最小值一般出现在春季和秋季。通过气溶胶类型分类可知,除了春季受沙尘大颗粒气溶胶影响外,北京地区高气溶胶主要 由城市细粒子气溶胶引起,且四季小粒子增长现象明显,其中夏秋季主要为吸湿性增长,其他季节主要为静稳天气下的增长。 对比沙尘和霾天气下气溶胶性质,结果表明:霾天气下AOD一般高于沙尘天气, Hysplit风场后向轨迹模型 结果表明,沙尘天气下气团为穿过蒙古草原和沙漠的西北风场。在灰霾天气下风场风速较小且主要以东南和西南风场为主,高气溶胶状 态为本地积累和外来输送共同作用产生。

Aerosol optical properties are investigated using the data observed by sun-photometer CE318 from 2011 to 2014 at Beijing station. It shows that the aerosol optical depth in Beijing, China is high for the whole year, the annual means of aerosol optical depth (AOD) at 440 nm for the four years are about 0.67±0.70, 0.69±0.71, 0.73±0.66 and 0.75±0.66, respectively. The average monthly AOD shows similar seasonal variation with a maximum in spring and a minimum in autumn. According to aerosol classification, high aerosol level in Beijing is mainly caused by fine particles and there are also coarse dust particles in spring. Fine particles growth is found in four seasons, which is mainly a hygroscopic growth in summer and autumn and a coagulation growth in other seasons. Comparison of aerosol properties between dust and haze condition shows AOD in haze condition is generally higher than that in dust condition. The back trajectory analysis indicates that airmasses on the dust day are northwest wind across Mongolia grassland and Gobi deserts. The wind speed on the haze day is weak and dominated by southeast and northwest wind, and high aerosol load condition is caused by local accumulation and transportation from other places.