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Zagolski F.,PARBLEU Technologies Inc | Santer R.,ADRINORD | Santer R.,University of the Littoral Opal Coast
International Journal of Remote Sensing | Year: 2016

Performing a classical atmospheric correction over water requires a well-defined climatology representative of the aerosols encountered in the remote areas of oceans. Different climatologies built up at the global scale are candidates to be implemented, as an auxiliary data file (ADF) including look-up tables (LUTs) with radiative properties of the aerosols, in a traditional atmospheric correction algorithm. In addition to these, two regional climatologies were developed in the 2-Seas region, comprising both the Eastern English Channel and the North Sea, and at the Acqua Alta Oceanographic Tower (AAOT) in the Adriatic Sea. By using the optical data processor of the European Space Agency (ODESA), Medium Resolution Imaging Spectrometer (MERIS) level-1 (L1) data extracted from the MERis MAtchup In-situ Database (MERMAID) were processed to obtain the level-2 (L2) products over water. For a given climatology, a full processing chain was developed to generate the MERIS aerosol LUTs suitable to ODESA. The final step consisted of an analysis of the L2 products, for both the aerosols and marine reflectance, in the framework of the evaluation of the performance of each climatology in atmospheric correction over oceans. Finally, we recommend using the regional aerosol climatologies available from the AErosol RObotic NETwork (AERONET) database, at least for the retrieval of the L2 aerosol product. In regard to marine reflectance, this remains more challenging and needs a more extensive analysis. © 2016 Taylor & Francis.

Aznay O.,ADRINORD | Santer R.,ADRINORD | Santer R.,University of the Littoral Opal Coast | Zagolski F.,PARBLEU Technologies Inc
International Journal of Remote Sensing | Year: 2014

A new approach has been developed to validate atmospheric correction (AC) over the ocean. The latter has been applied to the ground-segment data from the Medium Resolution Imaging Spectrometer (MERIS) on board the Environmental Satellite (Envisat) platform. An atmospheric validation database has been built up with a ground-based instrument, i.e. the Cimel radiometer from the Aerosol Robotic Network (AERONET). The aim of this work is to assess the atmospheric scattering functions needed to perform AC of remotely sensed data. The inputs to this new methodology were provided by AERONET, after inversion of radiometric measurements (i.e. solar direct extinctions and sky diffuse radiances) to get the inherent optical properties (IOPs) of the aerosols. The successive orders (SOs) of scattering code have been used as the radiative transfer tool in this study. This new concept for the validation of AC has been illustrated with the MERIS level-2 data extracted from the Meris Matchup In-situ Database (MERMAID) over the Acqua Alta Oceanographic Tower (AAOT, Venice - Italy). Results indicate first, an overestimate of the MERIS aerosol optical thickness (AOT) at 865 nm, and second, a marine reflectance affected by a negative bias of about 13% at 412.5 nm. This yields to an overestimate of the MERIS algal-1 pigment index, which may exceed 50%, over AAOT. The same trend is also observed in the determination of the algal-2 pigment index. © 2014 © 2014 Taylor & Francis.

Santer R.,ADRINORD | Santer R.,University of the Littoral Opal Coast | Aznay O.,ADRINORD
International Journal of Remote Sensing | Year: 2014

When clouds cannot be detected by a radiometry approach, the O2-A absorption band, located around 762 nm, can be used under clear sky conditions to perform this task. We present in this article a 5S-like formalism for the O2 band, based on single scattering approximation, aiming to isolate the aerosol contribution. The apparent pressure of the aerosols layer, derived from this new formalism, is used in the processing chain for the Medium Resolution Imaging Spectrometer (MERIS; on-board the ENVISAT platform) third processing to detect the presence of cirrus clouds over water. This formalism can be used as well over land to correct surface pressure, derived from the O2-A band, from the influence of the atmosphere. © 2014, © 2014 Taylor & Francis.

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