SEA SURFACEWIND RETRIEVAL USING BOTH NORMALIZED RADAR CROSS SECTION AND POLARIZATION RESIDUAL DOPPLER FREQUENCY FROM TERRASAR-X DATA

The polarization residual Doppler frequency (difference between the VV and HH Doppler centroids) is investigated as a valid parameter in a sea surface SAR wind retrieval scheme. This parameter along with the normalized radar cross section are used as inputs to two purely theoretical geophysical model functions based on the Generalized Curvature Ocean Surface Scattering model. A cost function minimization is implemented as part of the proposed wind retrieval method. The methodology is tested using 21 co-polarized TerraSAR-X scenes where retrieved winds are compared against collocated in situ measurements. A 5.23 degree bias along with a 45.3 degree standard deviation and 0.88 correlation are obtained for the wind direction comparison, while a 1.49 m/s bias, 2.36 m/s standard deviation, and 0.72 correlation are obtained for the wind speed comparison.