Future ocean scatterometry at very strong winds

The growing interest in achieving a better understanding of the physics that governs the cross-polar scattering of microwave radiation from ocean is triggered by recent measurement campaigns over hurricanes performed by NOAA Hurricane-Hunter winds and RADARSAT-2 [1]. From this data set the cross-polarized signals showed no evident loss of sensitivity as the wind-speed increased from 20 m/s up to 45 m/s. On the contrary C-band co-polar backscatter suffered from problems of incidence and azimuth angle-dependent signal saturations and dampening which makes it weakly sensitive above 25 m/s. On the basis of these considerations there are good reasons to think that the cross-polarized data can be a valuable tool for the retrieval of strong-to-severe wind speeds for future scatterometers. In this paper we present a physical scattering model based on the Small Slope Approximation theory [2] in conjunction with the Vector Radiative Transfer Theory [3] to describe the behavior of cross-polar scattering from ocean as function of the wind-speed and direction. Numerical results will be compared with real data from RADARSAT-2 and the brand new empirical Geophysical Model Function GMF-VH [1].