Ultrawideband, polarimetric radar studies of breaking waves at low grazing angles


  • Mark A. Sletten,

  • Jin Wu


This paper summarizes the results of recent laboratory investigations into the ultrawideband, polarimetric scattering properties of breaking water waves. Breaking waves were produced in a wave tank through chirped wave packets (0.5–1.0 Hz) generated by a programmable wavemaker. An ultrawideband radar system was then used to measure the polarimetric properties of the breakers over the 6–12-GHz band at a grazing angle of 10°. An analysis of the data from these experiments shows interesting dynamics in and differences between the dominant VV and HH polarizations. In particular, the RF frequency responses of the orthogonally polarized signals differ substantially, and both the magnitudes as well as the relative phases can change appreciably over relatively short time intervals. A “bench top” model of a breaker is used to support the hypothesis that this behavior is due to the presence of small, nonlinear structures near the breaker crest and a “double-bounce” scattering mechanism associated with them.