A numerical finite-difference time-domain(FDTD) approach for electromagnetic scattering from a dielectric target over randomly rough surface is developed in a three dimensional model.The rough surface is truncated in the simulation by using periodic surface extension.One period of rough surface is related to the surface correlation length.Generation of incident waves upon a rough surface is presented.Numerical model of a target on/above a rough surface is designed.Polarized bistatic scattering from the target and rough surface is obtained based on numerical distribution of near fields.A comparison of three-dimensional and conventional two-dimensional models is made.It shows that the back scattering from a rough surface is significantly enhanced due to the target on/above the rough surface.

As the scatterer's size is no less than or comparable with the wavelength, a rigorous solution of multiple scattering Maxwell's equation must be used. Multiple scattering formulation of T-matrix method is adopted to develop numerical simulations of polarized scattering from clustered spherical particles. Numerical results for coherent scattering from non uniformly clustered scatterers are presented. Numerical calculations are also well compared with experimental data of a two-sphere cluster.

Numerical approach to vector radiative transfer equation for a layer of densely random, spherical scatterers is discussed. The polarized brightness temperature and the functional dependence on various parameters are obtained, and are well compared with experimental data in snow remote sensing.