摘要:
利用2007年11月至2010年10月NCEP/NCAR再分析资料和HYSPIIT模式模拟了后向气流轨迹,分析了兰州大学半干旱气候环境观测站（SACOL）所在地区的大气输送特征.采用聚类分析方法将1096条轨迹分类,得到15簇反映主要特征的典型气流,研究了不同气流特征、出现频数及季节分布特点,与主要天气形势和天气系统的关系.统计主要气流路径所占比例,其中源于四川和重庆的气流占总路径的16%,为影响SACOL的主要路径,其次为源于局地和陕西的气流,路径最少的是东欧和孟加拉国.结合同期MFRSR地基辐射计反演的870nm气溶胶光学厚度和波长指数,分析了不同气团源控制下的气溶胶光学特性和粒了性质特征.揭示了最大平均气溶胶光学厚度达0.29±0.12（平均值±标准差）,气团源于塔克拉玛干沙漠;最小平均光学厚度的气团源于孟加拉国,为0.14±0.02.根据研究站点周围环境条件和气团源区地理条件以及移动轨迹,分析其可能影响,并定量给出不同源区气团对SAOL三年平均气溶胶光学厚度的贡献率.结果表明,源于局地和区域性气团贡献平均光学厚度的41.1%,沙尘区贡献28.4%,中亚为17.9%,远距离东欧和中东为12.6%.
Abstract:
Backward trajectories computed using the NOAA HYSPLIT model and global NOAA-NCEP/NCAR pressure level reanalysis data from November 2007 to October 2010,are used to trace air history and analyze the atmospheric transportation properties over SACOL.The cluster analysis has the advantage of providing highly disaggregated trajectory clusters,from which fifteen significant clusters arriving at the SACOL,which reflect the main feature of air mass trajectories,are obtained during this period.It is found that the air mass trajectories from Sichuan province and Chongqing account for 16%of all trajectories and have the biggest influence,those from local and Shanxi province have the second biggest influence,and those from the Eastern Europe and Bangladesh have the smallest influence.The Aerosol Optical Depth（AOD） at 870nm and Angstrom exponent acquired by a Multi-Filter Rotating Shadowband Radiometer（MFRSR） at SACOL are employed to analyze aerosol optical properties and particle characteristics under the control of different air mass sources.The maximum average AOD of 0.29±0.12（mean±standard deviation of mean） corresponds to the air mass originating from Taklimakan Desert,whereas the minimum average AOD is 0.14±0.02 from Bangladesh.According to ambient conditions of the studied site and the geographical conditions and moved track of air mass,the quantitative contributions of different sources to the three-year average AOD of 0.22 are investigated.The results show that the greatest contribution to the average AOD, accounting for almost 41.1%,came from local and regional sources,an additional important contribution from dust areas is about 28.4%of the average AOD,the contribution from the Central Asia source occupies 17.9%,that from Eastern Europe and Middle East is 12.6%.
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