Studies on accuracy of numerical simulations of emission from rough ocean-like surfaces

Numerical simulation of passive microwave remote sensing of ocean surfaces has a strict requirement of accuracy. This is because the key output of the simulations is the difference of brightness temperature between a rough su rface and a flat surface. Since the difference can be as small as 0.5 K, it is important to simulate the scattering and emission accurately. In this p aper, we perform accurate simulations of transverse electric (TE) and trans verse magnetic (TM) waves for ocean surfaces with relative permittivity = 2 8.9541 + i36.8430 at 19 GHz. Because ocean permittivity is large, we used u p to 80 points per free space wavelength. Furthermore, accurate numerical i ntegration is also performed to obtain accurate impedance matrix elements. To ensure accuracy, a matrix equation obtained from the surface integral eq uation formulation is solved by matrix inversion. Conservation of energy is required to be accurate to a relative error of 0.001, which corresponds to 0.3 K in brightness temperature. Numerical results are illustrated for rou gh surfaces with Gaussian spectrum and bandlimited ocean spectrum and bandl imited fractal surfaces. We show convergence with respect to the density of sampling points and with respect to raising the upper limit of the bandlim ited ocean spectrum. Comparisons are also made with results with an impedan ce boundary condition approximation. Numerical results indicate that fine d iscretization is required for ocean-like surfaces with fine scale roughness .