A COMPOSITE MODEL OF MICROWAVE SCATTERING FROM WATER SURFACE IN EXTREME WIND SPEED CONDITION

Abstract

Experiments were carried out in the wind-wave flume of Large Thermo-Stratified Wind-Wave Tank of IAP RAS aimed at studying the mechanisms of cross-polarized microwave radiation scattering from water surface under conditions of extremely high wind speeds. It is shown that the normalized radar cross-section (NRCS) can be represented as the result of an incoherent addition of contributions from breaking wave crests and from non-breaking wind waves. The effect of smoothing the water surface after passing the breaking crest made it possible to measure the NRCS of the breaking area on cross-polarization, while no dependence of the NRCS on wind speed and incidence angle was revealed. NRCS on non-breaking wind waves was calculated within the framework of the small slope approximation (SSA) using experimentally measured wind wave spectra. It is shown that the NRCS on cross-polarization increases monotonically with increasing wind speed, including hurricane conditions. In this case, the contribution of non-breaking wind waves to the NRCS saturates at wind speeds above 25 m/s. The monotonous increasing NRCS at higher wind speeds is associated with a breaking area increasing. A composite model of microwave radiation scattering from wave-covered water surface has been constructed, which has been verified on the basis of comparison with measurement data. The possibility of constructing a geophysical model function for ocean conditions based on the proposed composite model is shown, which can be used for remote sensing of sea storms and hurricanes.