环上海地区干霾气溶胶垂直分布的季节变化特征

采用2007年1月～2010年11月美国国家航空航天局(NASA)的CALIPSO星载激光雷达L1产品,通过532 nm总后向散射系数、体积退偏比和色比,分析了环上海地区干霾期间气溶胶光学和微物理属性的垂直分布特征.结果表明,干霾时各高度层中,0～2.0 km高度层的大气散射能力最强,且主要是规则气溶胶;2.0～8.0 km范围内各高度层大气散射强度、气溶胶规则性较接近;8.0～10.0 km高度层的大气散射能力最弱,且不规则气溶胶所占比例在各高度层中最大;细粒子气溶胶在各高度层均占主导地位,其中2.0～8.0 km范围内各高度层的细粒子气溶胶所占比例较大.春季大颗粒、不规则气溶胶所占比例大;夏季细粒子、规则气溶胶所占比例大.分析2007年5月7日个例发现,气溶胶粒子主要聚集在0～1.5 km范围内,在4.0～5.5 km范围内局部聚集;通过HYSPLIT轨迹模式分析表明,除本地排放的气溶胶粒子外,源于蒙古、中国西北和北部远程输送的沙尘也对霾产生了影响.

Seasonal Variations in the Vertical Distribution of Aerosols During Dry Haze Periods in Regions Around Shanghai

Based on the onboard lidar data from CALIPSO satellite of National Aeronautics and Space Administration (NASA) from January 2007 to November 2010, the vertical distribution of optical and micro-physical properties of aerosols around Shanghai during the haze periods when relative humidity less than 80% were revealed by analyzing the parameters of 532 nm total attenuated backscatter coefficient, volume depolarization ratio and total attenuated color ratio. The results showed that during dry haze periods, the scattering ability of lower troposphere (0-2 km) was the highest and the main constituents were regular aerosols. The scattering ability of the upper troposphere (8-10 km) was the lowest and the proportion of irregular aerosols was the highest among the five altitude layers. In addition, the scattering ability of the altitude range (2-8 km) was lower than that of the lower troposphere, and the scattering ability and irregularity of aerosols at different altitude levels within the range were close to each other. Fine particle aerosols were the dominant aerosols in altitude range of 0-10 km. To be noted, the proportion of fine particles decreased with increasing altitude within the altitude range of 2-8 km. The proportion of large and irregular aerosols were higher in spring, whereas the proportion of fine and regular aerosols were higher in summer. According to the analysis of a dry haze episode on May 7^th, 2007, it was found that a mass of aerosols mainly distributed within the altitude range of 0-1.5 km and partially within the altitude range of 4.0-5.5 km. The HYSPLIT model was applied to analyze the sources of aerosols in the episode, and the results indicated that the dry haze was mainly caused not only by local emissions but also by the dust aerosols transported from Mongolia, the northwest and north of China by the airflow.