SKY DOME CORRECTION FOR SEAPRISM AND TRIOS ABOVE WATER RADIOMETRIC MEASUREMENTS IN MERMAID

摘要

The water reflectance derived from in-situ measurementsrnrepresents a key element in the validation ofrnMERIS (MEdium Resolution Imaging Spectrometer)rnatmospheric correction over ocean. This above waterrnradiometry comprises simultaneous acquisitions ofrnsurface irradiance, downwelling sky radiance and waterleavingrnradiance which needs to be corrected for thernFresnel reflection of the sky dome by the sea surface.rnBy neglecting the polarization in this correction thernreflected sky radiance may induce a bias of severalrnpercents in relative error on the marine reflectance. Anrnalternative correction of the sky dome reflection hasrnthen been proposed accounting for the polarized naturernof the light scattered by the atmosphere and of thernFresnel reflection. Two sky dome correction tools havernbeen developed to be implemented in the MERMAIDrn(MERis MAtchup In-situ Database) processing chain ofrnin-situ data from AERONET-OC (SeaPRISM) andrnMUMM (TriOS). For each data sequence acquired overrna matchup, the correction is achieved using the aerosolrnparameters extracted from the MERIS level-2 product.