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A New Algorithm To Retrieve AOD With ATSR-2 Data


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C. Robles-Gonzalez, G. de Leeuw, R. Decae & J. Kusmierczyk-Michulec


The single and dual view algorithms for the retrieval of aerosol optical depth (AOD) and Angstrom coefficients in cloud free areas over sea and land using data from the Along Track Scanning Radiometer 2 (ATSR-2) on board the European Remote Sensing satellite (ERS-2) has been applied over the east coast of the United States [l, and 21 and over Europe [3]. In this contribution the generalisation of the algorithms for application over other areas is reported. A severe drawback during previous application to retrieve the AOD over Europe [3] was that over land there is no reliable cloud flag. Therefore a cloud-screening scheme developed by Koelemeijer and Stammes [4] was applied. This semi- automatic algorithm requires manual interference which renders the application very time consuming. Therefore, the first step to generalise the ATSR-2 algorithms was the inclusion of an automated cloud detection scheme. The next step was the inclusion of other aerosol types than the continental and sea salt aerosols that are included in the original algorithms. Optical properties of soot (black carbon) and dust aerosols have been used to prepare look up tables (LUT’s) for implementation in the ATSR-2 algorithms. Due to the fact that the algorithms will be tested with data from the INDOEX experiments, the aerosol data obtained from this experiment were used as inputs to determine the appropriate aerosol mixtures. Preliminary results from application of the algorithms to ATSR-2 data over the INDOEX area are shown. Comparison of the retrieved AOD with ground based sun photometer measurements from the AERONET data-base for the Male Island on 16th of February 1999 shows that the data agree within 0.05 at 0.659 pm.