Analysis of aerosol sources and optical properties based on backward trajectory method over SACOL

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 ngstrm 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%.