Experimental study of spectra and X and Ka band backscattering from the rain agitated water surface

摘要

Development of the technique for remote sensing of the sea state and wind parameters near the sea surface using the sea radar backscattering characteristics show that influence of the rainfall have to be taken in to consideration too. As shown in [1-4] even in case of moderate precipitation rain generated agitation on water surface caused the same intensity of CM and MM backscattering as the sea wave at wind with velocity of few meter per second. In the paper [1] the theoretical technique for estimation of the radar cross section (NRCS) of the stalk and of the single ring wave was proposed. But the results of this work can't be taken as the basis for the practical estimation because of some simplification assumptions regarding to the properties of the ring waves In the works [2-4] the calculation technique of the NRCS of the basin surface completely covered by the ring waves was developed on the basis approach of the Bragg scattering. It is known, that in such approach scattering completely defined by the spatial spectrum of the rough surface. In the paper [3] the approximation of the spatial spectra of the agitated surface was proposed basing on results of the experimental works and values of parameters for this approximation was estimated. However try to apply above mentioned approximations to the CM and MM wave radar grazing angles scattering shows that calculated values becomes on many orders lower then achieved in the experiments [7] or calculated by the equations proposed in [l]. The reason for this is seems that in case of low grazing angles CM and MM radio waves were scattered by the high frequency (short wave) spatial harmonics of the surface spectra spectra where proposed approximation does not describes actual spectrum of roughness.