Polarisation orientation angle measurements of ocean internal waves and current fronts using polarimetric SAR

Previous studies have shown that polarimetric synthetic aperture radar (POLSAR) data may be used to measure parameters such as bare surface roughness. Polarisation orientation angles, derived from POLSAR data, can be utilised to produce estimates of topography. Orientation angles have been used for SAR data compensation, in areas of rugged terrain, to ensure accurate estimation of geophysical parameters such as biomass and soil moisture. Orientation angles have also recently been investigated for use in measuring directional ocean wave spectra. Studies of these ocean features are conventionally done by measuring feature-related microwave backscatter intensity perturbations. In the work presented, a new approach is taken. Investigations have been made of changes in the polarisation orientation angle caused by ocean wave-current interaction features. The study uses airborne POLSAR data obtained in the New York Bight and in the Gulf Stream, east of Cape Hatteras. A model is used to determine the parametric dependencies of the orientation angle on internal wave current, wind-wave direction and wind-wave speed. An empirical relation is proposed to relate orientation angle perturbations to the underlying internal wave current strength.