MODIS Aerosol Optical Depth Inversion Over Urban Areas Supported by BRDF/Albedo Products

Aerosols play an important role in climate change and environmental pollution, and monitoring of aerosols via remote sensing is of great significance. However, for urban areas that are closely related to people's lives, remote sensing monitoring of aerosol optical depth (AOD) faces major challenges. These surface types, with bidirectional reflection characteristics, have a high surface reflectivity that is not sensitive to aerosol changes. Therefore, surface reflectivity must be calculated with high precision, which can be difficult using existing methods. To overcome these problems, this paper provides a MODIS AOD inversion method for complex background conditions that is supported by BRDF/Albedo products. Using these products, the accuracy of surface reflectivity and the resulting inversion results of aerosols are improved. Three typical complex background areas (Beijing, Baltimore and Paris) were selected for application testing. AOD inversion was calculated using MODIS BRDF/Albedo data for 6 years from 2012 to 2017. Accuracy was verified using the AERONET ground-based observations in the corresponding areas, and results were compared with the existing MODIS aerosol product (MOD04 AOD). Inversion estimates using this method have a higher correlation with AERONET AOD (R = 0.948). The root mean square error is 0.107, and 70.08% of the points are less than the expected error. When compared with MOD04 AOD products in urban areas, the inversion results of the new algorithm have higher precision and stability.