General Discussion on Electromagnetic Scattering

The purpose of this general discussion on e.m. scattering after the formal scientific presentations at the workshop was to ascertain the present state of knowledge in the field, assess the quality of the predictions, and to arrive at some specific recommendations for future research. Frank and active discussions took place in regard to the status of e.m. scattering theories/models for the ocean surface (see Table I). During the formal presentations it was clear that the two-scale model (Wright, 1968; Bass and Fuks, 1979) when properly applied, (Thompson, 1988; Thompson et al., 1988) yields just as good agreement (within a couple of decibels) as the Kirchhoff approximation (Holliday et al., 1986, 1987) when applied to the SARSEX data on SAR imagery (L and X band) for internal waves in the New York Bight. Both of these comparisons only deal with cross section effects, the distortion in the image intensity from wave motion and current variations affecting the phase of the e.m. backscattered fields is not included. To match the theoretical predictions with the measurements, the enhancement in slopes by the internal waves of both the long (greater than 1 m length) and intermediate (of the order of 1 m length) gravity waves should be included in the tilting of the Bragg resonant waves of wave number 2ko sinθ, ko is the wavenumber of the e.m. radiation in free space and θ is the angle of incidence.