On Doppler Shifts of Breaking Waves

Field-tower-based observations were used to estimate the Doppler velocity of deep water plunging breaking waves. About 1000 wave events observed by a synchronized video camera and dual-polarization continuous-wave Ka-band radar at incidence angles varying from 25 55 degrees various azimuths analyzed using computer vision methods. velocities (DVs) associated with waves were, for first time, directly compared whitecap optical measured as line-of-sight projection vector (LOV). The DV LOV found correlated; however, was systematically less than ratio dependent on angle azimuth. largest DVs up-wave down-wave directions accompanied an increase cross-section polarization ratio, HH/VV, up 1, indicating non-polarized backscattering mechanism. qualitatively reproduced in terms combination fast specular (coherent) slow non-specular (incoherent) returns two planar sides asymmetric wedge-shaped breaker. difference roughness tilt between breaker (the front face rougher rear face) explained asymmetry consistent previously reported mean sea surface centroid data normalized measurements.