不同季节南京市上空气溶胶的光学特性及垂直分布

Aerosol Optical Properties and Vertical Distribution in Different Seasons over Nanjing City

为了了解不同季节南京市上空气溶胶的光学特性,利用偏振微脉冲激光雷达对南京市上空大气散射特性进行了为期1年的连续观测,结合MODIS卫星数据分析了大气气溶胶光学特性的日变化和季节变化,并利用HYSPLIT模式分析了变化的原因。结果表明,①南京市上空气团在春、秋、冬季主要来源于中国西北以及北方地区,大气气溶胶消光后向散射比分别为48.4、45.3和39.6 sr,退偏振比分别为0.18、0.19和0.20;而夏季主要来源于中国东南部工业污染城市以及南京周边地区,消光后向散射比为63.2 sr,退偏振比为0.11;②大气气溶胶的垂直分布有明显的季节变化趋势,低层(<1 km)大气气溶胶光学厚度从大到小依次为冬季、夏季、秋季、春季,高层(>1 km)大气气溶胶光学厚度从大到小依次为夏季、春季、秋季、冬季;③大气气溶胶光学厚度有明显的日变化特征,主要分为2种类型,在夏季和冬季为早晚高中午低;在春季和秋季则逐渐升高。

Continuous observation of atmospheric diffusion properties in Nanjing was made by MPL for a year. The seasonal changes of optical properties of aerosol over Nanjing city were analyzed. Its reasons were studied combing with data of HYSPLIT. The results showed the air mass was mainly from northwestern and northern China at spring, autumn and winter, with the extinction-to-backscatter ratio of 48.4 sr, 45.3 sr, 39.6 sr, respectively. Depolarization ratio was 0.18, 0.19, 0.20 mainly from the southeastern China and the surrounding areas of Nanjing city at summer, with the extinction-to-backscatter ratio of 63 sr and depolarization ratio of 0.11. The vertical distribution of aerosol has significant seasonal variation. The orders of the optical depth from big to small were winter,summer,autumn and spring in low layer below 1 km. The order was summer, spring,autumn and winter in high layer above 1 km. The optical depth of aerosol has significant diurnal variation. AOD was higher in the morning and evening at summer and winter, and lower in the noon, increased gradually at spring and autumn.