Satellite remote sensing of aerosol parameters

Aerosol optical thicknesses, derived by satellite measurements, are only reliable over the ocean. Over land the separation of surface and atmospheric contributions to the TOA radiances is not straightforward due to the very variable surface characteristics. The proposed algorithms for a retrieval of aerosol properties above land surfaces deal with the dark pixel method, multispectral, multiangle or polarisation approaches. A closure experiment for the aerosol optical depth and multispectral radiances (LACE´98) has been performed for a clear sky and continental atmosphere in July/August 1998 nearby Berlin, Germany. Multispectral up- and downwelling radiances have been measured at different heights from an aircraft during 9 flights. Two sunphotometers (380-1100 nm), a compact airborne spectral imager (casi), and a zenith radiance measuring system have been installed onboard the aircraft. Additionally there have been probes for the chemical analysis of the aerosols. The observed quantities and ground based sun-photometer measurements serve as input data for the radiative transfer model MOMO (Matrix-Operator MOdell). If the measured and computed zenith radiances are in good agreement, the first step of the closure experiment is performed. Furthermore, it is planned to compare the simulated radiances to satellite data (SeaWiFS) and to investigate how accurate the aerosol optical properties can be inferred from satellite data