Assessment of ocean wave spectrum using global Envisat/ASAR data and hindcast simulation

Wave mode of spaceborne synthetic aperture radar (SAR) is designed for the global ocean wave observations. Despite fact that significant height inferred from SAR measurements has been validated against model output and in-situ data, SAR's primary unique capability operational 2-dimensional spectral description sea state remains to be fully evaluated. In this study, we extended previous assessment approaches by introducing a new image parameter, Mean rAnge Cross-Spectrum (MACS) focuses on isolated scales along line-of-sight direction. MACS an efficient variable in it characterizes local spectra properties without need non-linear inversion procedure. The based multiple-year data acquired Envisat/ASAR mode, with collocated WaveWatch III (WW3) hindcast buoy-observed spectra, which forward transformation systematically performed obtain simulated spectra. Inter-comparison between SAR-measured WW3-simulated demonstrates consistency wavelength (or wavenumber) dependent. Three typical wavelengths, around 62 m windsea, 168 intermediate waves 342 swell, are selected present comparison detail. Comparable magnitude observed while larger simulation values predicted windsea waves. Spatial distribution agrees well these two sets all wavelengths high correlation coefficients (>0.8) most ocean. One exception extratropics where quantitative difference particularly notable. contrary, when comparing buoys-simulated MACS, agreement increases towards shorter (<100 m) wavelengths. We also found large-scale atmospheric/oceanic features persistent images lead overestimate at long expected bias inversion. retrieval performance shall advance as such impact properly resolved.