Retrieving aerosol optical depth and type in the boundary layer over land and ocean from simultaneous GOME spectrometer and ATSR-2 radiometer measurements - 2. Case study application and validation

[1] Intensive research on the distribution of aerosols is being conducted within many international research programs (e. g., Global Energy and Water Cycle Experiment and International Global Atmospheric Chemistry Experiment). Obviously, satellite remote sensing allows for global monitoring; however, operational satellite observation has for a long time been limited to either the oceans or to UV-absorbing aerosols. Therefore a new aerosol retrieval method, Synergetic Aerosol Retrieval (SYNAER), to derive aerosol optical depth and type, both over land and over ocean, was developed (see part 1 of this paper, Holzer-Popp et al. [2002]). First, case studies showing its application and a validation using ground-based and airborne measurements are presented. They show a good agreement with better than 0.1 in boundary layer aerosol optical thickness at 550 nm and indicate a detection of the correct aerosol type in most cases. Restrictions for the detection of aerosol type appear over bright surfaces and in areas with an aerosol optical depth less than 0.1 due to a low aerosol sensitivity in these situations. The method has been developed for the future operational use of similar sensor pairs Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY)/Advanced Along Track Scanning Radiometer (AATSR) and Global Ozone Monitoring Experiment 2 (GOME-2)/Advanced Very High Resolution Radiometer (AVHRR). Thus SYNAER holds the potential to extract a 25-year-long climatological data set (1995-2020) from ERS-2, Envisat, and METOP.