Abstract
The derivation of aerosol parameters using polarimetric measurements by the airborne version of POLDER (POLarization and Directionality of the Earth’s Reflectance) over the Mediterranean sea is described. The degree of polarization of the upwelling radiation at the altitude of the airplane is computed by the doubling-adding method using a realistic atmosphere-ocean model. By comparison with measurements, characteristics of the aerosols over the ocean are inferred. The degree of polarization for the lunge size distribution with v=3.5 for small optical thickness, viz., τaer≤0.1, shows features most similar to the measurements. The simulation indicates that the wind direction has little effect on the degree of polarization of the upwelling radiation, whereas whitecaps greatly reduce the degree of polarization. In the solar plane, the computed degree of polarization agrees well with the measurements for τaer≤0.1 if the effect of whitecaps is excluded, whereas it is several percent smaller than the measured values near the backscattering direction. The computed minima of the degree of polarization are located at θ=38°, closer to the nadir than in the measurements.
