Simple model of a polarized bidirectional scattering cross section at 10.6 mum: application to SiO(2) sand

A model is proposed to interpret the polarized scattering behavior for natural soils. The model is based on the vector radiative transfer equation and is developed to the second order. Higher orders are modeled with a simple expression. The particles are assumed to have a large dimension with respect to the wavelength, allowing for the light to be locally specularly reflected. Apart from the complex refractive index, the model has only one extra parameter directly related to the compactness of the medium. Predicted values are compared with carefully calibrated measurements of the polarized bidirectional scattering cross section obtained with coarse SiO(2) sand. The model parameters retrieved from the fit are quite realistic. Good agreement is obtained between model-computed and experimental data for the angular behavior and the amplitude, without further adjustment. Comparison between model-computed total unpolarized bidirectional scattering cross section, Hapke's nonpolarized model, and measurements also shows good agreement.