Comparison of wave parameters measured from the SIR-C on-board processor with WAM predictions in the Southern Ocean

During the SIR-C (Shuttle Imaging Radar) mission in 1994, an APL-built on-board processor computed image spectra from the synthetic aperture radar (SAR) C-band signal. The image spectra, acquired for the purpose of estimating two-dimensional ocean wave energy spectra, were transmitted to the ground in real time. The author compares the dominant wavelength, propagation direction and significant wave height (SWH) estimated from processor spectra (with additional post processing) with nearly co-located estimates from the WAM (Wave Model) global wave model, as implemented by the U.S. Navy Fleet Numerical Meteorology and Oceanography Center (FNMOC). It is demonstrated that despite significant scatter, there are no systematic biases between SAR and WAM estimates of wavenumber and propagation direction. The SAR tends to underestimate SWH at SWHS greater than 4 m. This discrepancy is removed with a simple linear adjustment.