Comparison of ocean wave spectra from a non-linear SAR inversion scheme using ERS-1 and SIR-C/X-SAR data sets

Directional ocean wave spectra obtained with a fully non-linear inversion scheme from synthetic aperture radar (SAR) ocean image spectra collected by SARs onboard ERS-1 and the space shuttle (SIR-C/X-SAR) are compared. First results using spectra obtained within 500 km and five hours of each other indicate that the resulting spectral shapes and wave directions agree well. Spectral intensities and significant wave heights, however, are found not to agree well when the theoretical form of a hydrodynamic modulation transfer function (MTF) derived from orbital velocity straining alone is used. Agreement is improved when an empirical hydrodynamic MTF obtained from tower-based measurements is used.