Oceanic fronts as a source high air-sea flux due to breaking of standing waves of intermediate scale

Marine radar sea scatter experiments were conducted as part of a remote sensing and fluid modeling program to study littoral ocean properties toward an improved understanding of ship and airborne radar ocean imaging. In particular, radar backscatter data were collected using an X-band marine radar at low grazing angles near oceanic fronts and internal gravity waves. These data were collected from a ship that passed perpendicularly through both type of linear oceanic features, so that their azimuthal aspect sensitivity could be studied and related to the fluid dynamics driving them. While the internal waves appeared different from either side of the crest, the polarization properties associated with fronts was the same as seen with either aspect. The authors hypothesize that standing waves occur at fronts and act as a scattering source rather than asymmetric bores that have previously been identified at strong radar scatterers at horizontal polarization in wind driven seas. A simple propagation model of waves into a current shear region is used to show that intermediate waves of a 10 to 30-cm scale are reflected from the current profile at a front and can produce such standing wave scattering sources