Further numerical studies of backscattering from time-evolving nonlinear sea surfaces

Previous studies have demonstrated that the West et al. (1987) numerical model for nonlinear hydrodynamic evolution of a sea surface produces significant features in calculated L-band backscattered Doppler spectra compared to a linear sea surface evolution model. These prior comparisons were limited, however, to a maximum wind speed of 2.0 m/s due to failure of the West et al. algorithm when steep short-wave features formed on the surface. In this paper, L-band Doppler spectra with the West et al. model are reported for wind speeds up to 5.0 m/s through the use of a curvature filter to reduce these steep short waves. The higher wind speed results again show significant deviations from those reported with a linear hydrodynamic model, including increased spectral broadening and polarization dependencies.