Validation of ENVISAT ASAR Wave Mode Level 1 and 2 products using ERS SAR data

A preliminary validation of the ASAR Level 1b (cross spectra) product and the Level 2 (wave spectra retrieval) algorithm have been conducted using ERS Wave and Image Mode SLC data collocated with in-situ measurements and numerical wave model. The objectives of the validation have been to optimize the algorithms, the processing settings and to predict the performance of the new products and algorithms. For the Level 1b product, the main focus of the validation test has been on the resolution of the propagation direction and the establishment of RMS errors (as compared to simulated spectra) for the main swell spectral parameters. The main result is that when ocean swell system was detected the propagation ambiguity was resolved in 93% of the cases. The spectral peak wavelength and propagation direction RMS were 50 m and 40°, respectively. The mean peak wavelength was for this data set 265 m, and the average azimuth cut-off value was 256 m. The authors conclude that the cross spectra product of the ENVISAT Wave Mode is superior to the existing ERS Wave Mode product in terms of signal-to-clutter ratio and propagation ambiguity. For the Level 2 development the preliminary results shows that a consistent inversion scheme can be formulated without using any a priori information or first guess spectrum. Initial validation results shows that the wave spectrum within the SAR domain are unambiguously resolved in 80% of the cases processed. In the remaining 20% of the cases, ocean swell is not present (does not exist or not detected by the SAR) or directional informations not resolved