Estimation of sea surface wind vector using RADARSAT data

Synthetic aperture radars (SAR) have higher spatial resolution than scatterometers and we can obtain more detailed wind vector information from space-borne SAR data. This type of high spatial resolution wind information can be very useful particularly in coastal regions, where the scatterometer wind information can be altered by the coastal effects because the larger footprint spatial averaging of backscattered energy is unavoidable. This paper tested RADARSAT data with CMOD_4 and CMOD_IFR2 algorithms for extracting wind information over selected coastal test areas around the Korean peninsula. Because the CMOD algorithms were originally developed for the C-band, VV-Polarized scatterometer data, we applied currently available polarization ratio models (e.g., Kirchhoff, Elfouhaily, and Thompson models) for RADARSAT data processing. Three test areas, the West Sea and East Sea on both sides of the Korea peninsula and the open sea off Jeju Island, were tested with the RADARSAT Fine, Standard, and ScanSAR beam mode data. The correlation of the wind vector results with the buoy and meteorological station data agrees well with each other but with some variations. The RMS error for the SAR-derived wind direction is somewhat great, and the wind speed RMS error using CMOD_4 algorithm is about 1.7 m/s (Kirchhoff), 1.84 m/s (Elfouhaily), and 2.4 m/s (Thompson polarization ratio model), respectively.