A simple analytical model for brightness modulations caused by submarine sand waves in radar imagery

Abstract

Presented here is a simple analytical model based on established physics of the magnitude of the hydrodynamic modulations caused by sand waves. 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 of sand waves is incorporated. An assessment is made of the key parameters (shape, oceanographic, meteorological and radar) that influence the radar backscatter modulation. It is shown that depth, steepness of the slope, and height of the sand wave are the shape parameters that determine the radar backscatter modulation. The maximum backscatter modulation that can be found for sand waves in nature is approximately 3 dB. It is shown that sand waves in the North Sea near the Dutch coast have a linear relation between their heights and slopes. Implementation of this relation simplifies the model further. Furthermore, backscatter modulations calculated with two radar backscatter models are compared and discussed. The correlation between predictions and measurements with the airborne imaging radar of NASA's Jet Propulsion Laboratory is considered encouraging. Measurements from the images indicate a relation between sand wave height and brightness modulation similar to that predicted by the model.