A SIMPLE ANALYTICAL MODEL FOR BRIGHTNESS MODULATIONS CAUSED BY SUBMARINE SAND WAVES IN RADAR IMAGERY

Presented here is a simple analytical model based on established physi cs of the magnitude of the hydrodynamic modulations caused by sand wav es. The model describes the modulations of the radar backscatter when first-order Bragg scattering is assumed. The major difference between this model and existing analytical models is that the specific shape o f sand waves is incorporated. An assessment is made of the key paramet ers (shape, oceanographic, meteorological and radar) that influence th e radar backscatter modulation. It is shown that depth, steepness of t he slope, and height of the sand wave are the shape parameters that de termine the radar backscatter modulation. The maximum backscatter modu lation that can be found for sand waves in nature is approximately 3 d B. It is shown that sand waves in the North Sea near the Dutch coast h ave a linear relation between their heights and slopes. Implementation of this relation simplifies the model further. Furthermore, backscatt er modulations calculated with two radar backscatter models are compar ed and discussed. The correlation between predictions and measurements with the airborne imaging radar of NASA's Jet Propulsion Laboratory i s considered encouraging. Measurements from the images indicate a rela tion between sand wave height and brightness modulation similar to tha t predicted by the model.