Measurement of sea surface displacement with interferometric radar

The technique by which interferometric radar can measure the time-varying sea surface displacement is outlined, and an experiment to test the performance of this technique is described. A high-resolution X-band imaging radar with spatial resolution of 40 cm was deployed from a small pier observing an area approximately 20 m 3 20 m. Radar-derived surface wave heights and orbital velocities were compared to measurements made by a resistive wave wire deployed nearby. Consistency between wave height and velocity measurements, and good agreement of radar and wave-wire height statistics were found. Comparison of significant wave height measurements with the in situ sensors shows a correlation of 0.92, with a slope of 0.97 and an intercept of -0.001 m. Although observed wave heights were small, the good agreement obtained indicates the fine sensitivity of the interferometric technique to measuring surface wave heights. The technique should be applicable to any appropriately configured coherent radar with spatial resolution sufficient to resolve surface waves.