Spectral nonlinearities of the gravity-capillary waves and their effect on sea surface radar signatures

To investigate the effect of the nonlinear wave-wave interactions, on the gravity-capillary spectral form, and to draw conclusions for the geophysical interpretation of sea surface SAR imagery, a numerical study has been carried out. Spectral anomalies, strongly susceptible to influences by oceanographic features (e.g. slicks or currents) are shown. These are narrow bands, of wind dependent energy depressions, related to the excitation of capillary waves. The more enhanced of them appear at the early stages of the spectrum development, in the neighborhood of 100 rad/m wave numbers. An opposite surface current or a slick accentuate them while they become weaker at mature spectral stages, and by the induced wind drift current.