Analytical approach to estimating aerosol extinction and visibility from satellite observations

This study investigates the application of satellite data to the evaluation of aerosol extinction and visibility, for a better understanding of the spatio-temporal variation of local air quality in urban areas. A new analytical model based on aerosol microphysics and non-linear exponential fitting was applied to the analysis of aerosol extinction using aerosol optical thickness (AOT, τa) data retrieved from the MODerate-resolution Imaging Spectroradiometer (MODIS), over one of the largest global megacities: Seoul, Korea. The relationship between the MODIS τa and ground-based aerosol measurements of particulate matter mass concentration, extinction, and surface visibility was assessed over Seoul, Korea, during eight intensive observation periods in 2007–2009. The results clearly demonstrate that satellite-derived τa is a good surrogate for monitoring aerosol extinction and visibility over this study area. In particular, it is found that MODIS-estimated visibility values have a closer relation to the observed values than traditionally assumed Koschemeiderʹs relation. The analytical results shown in this study can provide a better understanding of aerosol extinction and visibility in megacity, as well as for routine visibility monitoring.