RADARSAT-1 ScanSAR SWA images of Hurricane Katrina are used to retrieve the surface wind vectors over the ocean.
Due to the inadequate spatial resolution of the ScanSAR SWA images, the spectrum method cannot be implemented to
estimate the wind direction. Instead, collocated H*wind wind directions are used as wind direction estimates. The wind
speed is derived from the σ° by inversion of a C-band HH-polarization Geophysical Model Function (GMF), which is
derived from C-band VV-polarization GMF using a polarization ratio model. Because existing polarization models don't
fit the ScanSAR SWA data well, a recalibration model is proposed to "recalibrate" the ScanSAR SWA images. The
coefficients of the recalibration model are "tuned" using collocated H*wind surface wind fields. To validate the SAR-retrieved
wind speed, the mean and the RMS difference between SAR-retrieved and H*wind wind speed estimates are
calculated. The mean of difference is small and the RMS for wind speed less than 25 m/s is below 4 m/s, suggesting that
the high resolution wind retrieval algorithm can work under hurricane conditions. Except for the influence from rain, the
largest errors occur at high wind speed (over 25 m/s), which is mainly due to the saturation of the C-band GMF CMOD5.