SCATTERING PROPERTIES OF DENSE MEDIA FROM MONTE-CARLO SIMULATIONS WITH APPLICATION TO ACTIVE REMOTE-SENSING OF SNOW

Monte Carlo simulations are used to derive the phase matrix, effective permittivity, and scattering coefficient for a random medium consisti ng of densely packed spheres up to 5000 in number. The results include correlated scattering and coherent wave interaction among the scatter ers. The Monte Carlo simulations are based on a multiple-scattering fo rmulation of the Foldy-Lax equations. It is shown that the derived pha se matrix is in good agreement with dense media radiative transfer the ory for copolarized scattering. The depolarization, however, can be su bstantially larger than conventional theory. Two methods are used to a nalyze the behavior of the coherent wave to obtain the real part of th e effective permittivity. For the small particle case both methods yie ld values of permittivity that agree with the results of mixing formul as such as the Clausius-Mossoti mixing formula. The phase matrix and s cattering coefficient obtained by simulation are used in a second-orde r radiative transfer model to predict the amount of backscatter from a layer of snow. It is also shown that sticky spheres, which can be use d to model metamorphosed snow, produce high levels of copolarized and depolarized backscatter that can exceed the independent scattering mod el.