A modified physical optics model of the rough surface reflection coefficient

Several models for the rough surface reflection coefficient have been compared to measured data at microwave frequencies. The physical optics model is shown to adequately model the level of the data, but not the angular migration of the Brewster angle for /spl upsi/ polarization as the surface roughness increases. The small perturbation method is shown to accurately model the data for surfaces of modest roughness (/spl kappa//spl sigma/=0.5), including the Brewster angle migration, but fails for a rougher surface with /spl kappa//spl sigma/=1.5. A rough surface reflection coefficient derived from the work of Ohlidal and Lukes [1972] is better than the physical optics and small perturbation methods for both surfaces, but it does not predict equal /spl upsi/ and h reflectivities at the nadir. A model based on the physical optics approach is presented which has equal /spl upsi/ and h reflectivities at the nadir and also closely fits the measured data.