Abstract:

The aerosol optical depth (AOD) can be retrieved accurately with sequential ground - based measurements of the direct and diffuse solar radiance. However, spatial coverage and location frequency cause certain limitations. Hence, satellite image data are a proper tool for obtaining aerosol optical depth products with more spatial information and patterns of aerosol distribution. Currently, aerosol remote sensing may enhance our understanding of the optimal approach of AOD retrieval over urban and rural areas and could differ due to the characteristics of surface reflectivity. In this study, the concepts of contrast reduction and dark target approaches are examined with Landsat image and the observation of sun photometer (AERONET) for integrating AOD distribution over Taipei city in Taiwan. For the areas with bright surfaces such as urban area, the above concepts are applied by dispersion coefficient method together with sun photometer in order to considerably reduce errors in the product. In contrast, the dark target algorithm with the relationship of surface reflectance between blue (0.49 μm), red (0.66 μm), and infrared (2.1 μm) spectral bands, is suitable for moist soils and vegetation areas. The retrieval of AOD spatial distribution is compared with MODIS AOD products and AERONET for verifying the accuracy of the result. The RMSE ranged from 0.2 to 0.4, and about 50% amount of data were within expected error (EE=± (0.05+0.15 AOD sunphotometer).