Comparison of RADARSAT SAR-Derived Winds with Buoy and QUIKSCAT Measurements

Over the last two years, we have processed 2862 RADARSAT wide-swath SAR image frames into high-resolution (600 m) estimates of wind speed. These estimates are generated by combining SAR radar cross section and wind directions from the global Navy Operational Global Atmospheric Prediction System. In performing the inversion to wind speed we used the CMOD4 model function for VV polarization and a function for mapping C-band VV polarization to the HH polarization of RADARSAT.

Here we present results of comparing the retrieved winds with buoy and model wind speeds. Thus far we have three major conclusions: (1) The standard deviation between buoy and SAR-estimated wind speed is 1.7 m/s. (2) The wide-swath SAR imagery as processed by Alaska SAR Facility underestimates radar cross section and hence wind speed for incident angles less than 25 degrees. (3) The polarization ratio used to relate wind speed and direction to HH polarization radar cross section shows the best agreement between SAR and buoy and SAR and model wind speeds when the "alpha" parameter is set equal to 0.6.

In addition, we will present preliminary results of comparing RADARSAT wind speeds with QuikSCAT scatterometer wind speed measurements.