AN ANALYTICAL MODEL FOR THE CLOUD-FREE ATMOSPHERE OCEAN SYSTEM REFLECTANCE

An analytical model for the estimation of spectral and directional reflectance over the ocean is developed. The model accounts for the first and second orders of reflection at the ocean surface, and/or scattering by the atmosphere and the water column. The model parameters are the optical thickness and Angstrom exponent of aerosols, the spectral albedo of the ocean, and the directional specular reflectance of the ocean surface (glitter), the latter being a function of the wind speed and direction. We show that our analytical model is sufficient to predict all reflectance angular and spectral variations by comparing its results with a Monte Carlo simulation that accounts for the higher orders of scattering. Using this analytical model, actual bidirectional and spectral measurements are easily inverted in order to retrieve geophysical and optical parameters of the ocean-atmosphere system (the application to the data acquired by the Airborne POLDER is developed in a companion article).