Radiative Transfer Code Comparison for Meris Vicarious Calibration

Different groups are involved in the MERIS vicarious activities. Most of the time, the prediction of the incoming radiance to the sensor needs radiative transfer computations. An inter comparison exercise is reported here based on radiative transfer computations with different codes applied on suitable test cases for vicarious calibration. Because the top of atmosphere signal over bright targets mostly depends upon the surface reflectance, a good agreement appears for vicarious calibration over land. Over the dark ocean, first, there is a need to account for the polarization mostly for the molecular scattering. Second, large discrepancies result from the computation of the aerosol scattering which have to be more deeply understood.