Investigation Of The Distribution Patterns Of Atmospheric Aerosol Optical Depth Via Remote Sensing Over The Yangtze River Delta

Considerable research has focused on the investigation of optical and physical characteristics of atmospheric aerosols along with the evident influence of the arising global climate variation and air quality deterioration on human life. One of the aerosol optical parameters defined to describe the physical and extinction characteristics of atmospheric aerosols, the optical depth, was the critical factor for the estimation of the concentration of atmospheric aerosols, the evaluation of the rating of atmospheric pollution as well as the investigation of the climate effect of atmospheric aerosols but the distribution features of atmospheric aerosols on regional scales, in present situation, can be detected with the help of the only way the remote sensing technique. In this study, the regional distribution pattern of atmospheric aerosol optical depth over the Yangtze River Delta was thus investigated via satellite remote sensing.Based on the dense dark vegetation algorithm and6S radiative transfer code, the MODIS satellite data was used to retrieve atmospheric aerosol optical depth over our research region and then the retrieving cases in seasonal scales were analyzed in detail. The aerosols optical thickness estimated from the ground-based sun photometer at the same time as the pass of the satellite were used to retrieval from satellite data. The study result shows that the aerosols optical thickness could be used to monitoring atmospheric aerosol optical depth in Yangtze River Delta. The aerosol data detected by MODIS was used to study the distribution patterns of atmospheric aerosol optical depth over the Yangtze River Delta since the year of2000. The results via the analysis of these data shown that the annual averaged atmospheric aerosol optical depth over this area was0.65for one year,0.78for summer,0.75for spring,0.55for autumn, and0.51for winter and thus obviously the distribution pattern in seasonal scale was the lowest optical depth in winter and largest optical depth in summer. While the distribution pattern over spatial scale was a high-value region located at Shanghai and the Hangzhou Bay and the decrease trend from this high-value region to surrounding areas. The high-value region mostly covered the coastal areas of Nantong, Suzhou, Shanghai and the south part of the Hangzhou Bay and the atmospheric aerosol optical depth over Shanghai was largest, that over Jiangsu the second, and that over Zhejiang the third. Furthermore a significant negative correlation between atmospheric aerosol optical depth and the terrains over the whole research area were detected as0.512.The distribution patterns of atmospheric aerosol optical depth and Angstrom parameter of Nanjing University of Information Science&Technology (NUIST), Taihu Lake, Thousand Islands Lake and Zhejiang Forestry College (ZFC) were investigated via the data from ground-based observing sites as well. Results indicated that the monthly averaged atmospheric aerosol optical depth of NUIST was0.64the maximum, that of ZFC was0.61the second, that of Thousand Islands Lake was0.60the third and that of Taihu Lake was0.58the minimum. The site of Thousand Islands Lake represented the largest value of monthly averaged Angstro’m wavelength index a of these four sites, followed by ZFC, Taihu Lake and NUIST. Indicating that small particles were main control particle size and aerosol particles were small of Thousand Islands Lake, while larger particles were main control particle size and aerosol particles were larger of NUIST. The atmospheric turbidity coefficientsβ of these four sites were in the range of0.28to0.36that indicated the high turbidity in the air and high concentration of atmospheric aerosol particles over this Delta.