Upwind-downwind asymmetry of the sea backscattering normalized Radar cross section versus the skewness function
Résumé
From the first-order small slope approximation, this
paper presents a closed-form expression of the sea backscattering
NRCS (normalized radar cross section) versus the skewness
function to predict the upwind-downwind asymmetry. This effect
is produced by the fact that the surface height distribution
slightly deviates from a Gaussian one. Introducing the azimuthal
property of the sea height autocorrelation and skewness (spatial)
functions, the integration over the azimuthal direction can be
done analytically, whereas the integration over the radial distance
can be done by using the property that the skewness correlation
distance is much smaller than that of the gravity waves. Then,
the backscattering NRCS is expressed from the sea skewness
spectrum at a wave number different of the Bragg wave number.
In addition, a simple inversion algorithm is proposed to perform
the parameters of the skewness function from experimental data
in C and Ku bands.