Retrieval of aerosol optical depth from satellite measurements using single- and dual-view algorithms

Abstract

To retrieve aerosol properties from the radiance measured at the top of the atmosphere in clear sky conditions, the contributions of the surface and the various atmospheric constituents need to be separated. This is easiest done over dark surfaces, i.e. with a negligible reflectance that can relatively easily be accounted for. This principle has been used for the retrieval ofaerosol optical depth (AOD) over water from satellite observations in the near-infrared. The AOD at wavelengths in the UV can be determined both over water and over land, using the same principle of a dark surface. For longer wavelengths, the dual view provided by ATSR-2 is used to separate the aerosol reflectance from the surface contribution. Single and dual-view algorithms have been developed by TNO-FEL and tested for the US east coast and over Europe. Currently the algorithms are extended with other aerosol types and tested versus data over the Indian Ocean (INDOEX area) and South Africa (SAFARI experiment). The initial results indicate that the AOD can be retrieved within reasonable limits. Apart from the ATSR-2, algorithms aimed at the determination of aerosol optical depth and composition are developed for AATSR and SCIAMACHY (ENVISAT) and OMI (EOS-TERRA).