On the Effects of Sea Surface Skewness Function and Its Parameter Related to Small-Scale Waves on Radar Backscattering: A Numerical Study

Sea surface skewness function used to describe the horizontal asymmetry of the sea surface is related to the third-order cumulant of rough sea surface, which is a key input for the modeling of radar scattering from non-Gaussian sea surface. The horizontal asymmetry of the sea surface is caused by small-scale sea waves and affects the radar echoes when the radar views the sea surface along different wind directions. However, currently, the sea surface skewness function and its parameters related to small-scale waves are diversified and there is no clear guidance in their choice. To this end, this letter first evaluated the effects of different skewness functions and small-scale wave components on the radar backscattering from non-Gaussian sea surface based on the first-order small slope approximation (SSA1) model. Then, the optimal skewness function and its parameter related to small-scale waves were determined by comparing the simulated backscattering contributed by different skewness functions with various small-scale wave components with radar measurements. Further, the performance of the SSA1 model with the optimal skewness function was compared with that of the two-scale model (TSM) including hydrodynamic modulation. Clarifying the effect patterns of skewness function and small-scale wave components on the radar scattering from non-Gaussian seas is instructive for us to model the radar scattering from the real sea surface, serving the optimization of radar observation scheme for the effective retrieval of sea surface wind field.