Comparison of slope-derived and height-derived modulation transfer functions for radar return and ocean waves

Use of a radar vector slope gauge at the SAXON experiment allowed new types of studies of the modulation-transfer function (MTF) between ocean waves and radar signals. The MTF calculated from slopes shows less coherence than that using heights, suggesting flaws in the usual application of linear, long-crested wave theory to MTF determination. In complex situations with multiple wave trains, the slope-derived MTF is related the most to the wave train traveling nearly toward the radar, regardless of wind direction, but coherence is low. This low coherence with slope and phase of the height MTF suggest that cross-wave radar signal modulation is largely hydrodynamic