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

摘要

The water reflectance derived from in-situ measurements represents a key element in the validation of MERIS (MEdium Resolution Imaging Spectrometer) atmospheric correction over ocean. This above water radiometry comprises simultaneous acquisitions of surface irradiance, downwelling sky radiance and waterleaving radiance which needs to be corrected for the Fresnel reflection of the sky dome by the sea surface. By neglecting the polarization in this correction the reflected sky radiance may induce a bias of several percents in relative error on the marine reflectance. An alternative correction of the sky dome reflection has then been proposed accounting for the polarized nature of the light scattered by the atmosphere and of the Fresnel reflection. Two sky dome correction tools have been developed to be implemented in the MERMAID (MERis MAtchup In-situ Database) processing chain of in-situ data from AERONET-OC (SeaPRISM) and MUMM (TriOS). For each data sequence acquired over a matchup, the correction is achieved using the aerosol parameters extracted from the MERIS level-2 product.