The inversion of the non-Gaussian slope probability density function of the ocean waves by KuROS radar measurements

Abstract

It is known that the slope probability density function (pdf) of the sea surface is non-Gaussian and can be expressed as a Gram-Charlier to fouth-order expension, including seven parameters: slope variances in upwind and crosswind direction, two skewness coefficients and three peakedness coefficients. Cox and Munk[1] had gotten all the seven parameters varying with the wind speed using optical data. However, those parameters for the sea surface at optical band and microwave band are different, and until now it is not clear for microwave band what values the seven parameters are. Wave scatterometer is a kind of microwave sensor specially designed for wave spectrum remote sensing and could provide σ0 in high resolution of the range and azimuthal direction so that it is possible to remote sense the slope pdf for a certain space-time. In this paper, firstly, the accuracy of Geometric Optical (GO) model is evaluated, which is used for confirming the valid range of incidence angle to invert; then, a two dimensional (2D) inversion method is developed for remote sensing all the seven parameters in non-Gaussian slope pdf by the wave scatterometer based on GO model; finally those parameters are inverted by the method using the Ku-band airborne wave scatterometer KuROS measurements.