基于飞机观测的四川盆地初夏云下气溶胶特征

Aerosols Characteristics Beneath the Clouds Based on Airborne Observation in Early Summer over Sichuan Basin

利用2009年6月23日夏延飞机搭载的云粒子测量系统(PMS)对四川盆地上空云和气溶胶的2次观测试验资料和MODIS光学厚度产品及云和辐射资料(CERES SYN1deg-3Hour Ed3A),结合HYSPLIT模式模拟的气团后向轨迹和前向轨迹,分析四川盆地云下气溶胶数浓度垂直分布、谱分布和来源特征。结果表明:飞机观测的四川盆地大气气溶胶数浓度量级为108~109m^(-3),与河北省、北京及周边城市飞机观测的气溶胶数浓度量级相同,污染较重。远距离输送对四川盆地气溶胶贡献小,说明气溶胶主要受盆地区域内污染物影响,同时气溶胶生成后主要在盆地区域内聚集,使得区域内空气污染居高不下。初夏阴天天气条件下,四川盆地的大气气溶胶主要分布在2 800 m以下,气溶胶粒子数浓度越靠近地面越大,且云下气溶胶粒子较多是积聚模态,粒子Angstr9m波长指数介于1.2~1.4之间,城市-工业气溶胶的特征明显。

With the purpose of studying the clouds and aerosols over Sichuan Basin,two observation experiments were performed with the PMS probes mounted on a CheyenneⅢA aircraft on June 23,2009.Based on the in-situ airborne observation data,CERES SYN1deg-3Hour Ed3A data,aerosols optical depth of MODIS and backward and forward trajectories simulated by HYSPLIT model,the vertical distribution,size spectrum distribution and source of aerosols beneath the clouds over Sichuan Basin were analyzed.The results show that the number concentration magnitude of atmospheric aerosol particles observed by the airborne over cities of Sichuan Basin was 10 8 to 10 9 m-3,which was identical to the number concentration magnitude of aerosol particles over greatly polluted cities of Hebei Province,Beijing and its surrounding areas.The aerosols over Sichuan Basin were impacted mostly by the regional pollutants,while the long-distance transportation had a little contribution to aerosol particles over Sichuan Basin.After the generation,the aerosol particles concentrated mainly over Sichuan Basin,which intensified the regional air pollution.On overcast days of early summer,the atmospheric aerosols were mainly below 2 800 meters AMSL over Sichuan Basin.The aerosol particles were nearer to the ground,and the number concentration was higher.In additional,the aerosol particles beneath the clouds were majorly accumulation mode,and Angstr m exponents of aerosol particles were 1.2 to 1.4,which obviously demonstrated the urban-industry aerosol characteristics.