Physics of backscattering in terms of mode coupling applied to measured seabed roughness spectra in shallow water

Abstract

Energy conserving coupled integral equations for the forward and backward propagating modal components have been previously developed [J. Acoust. Soc. Am. 130, 2673–2680 (2011)]. A rough seabed surface leads to a backscattered field and modifies the interference structure of the forward propagating field. Perturbation theory applied to the basic coupled integral equations allows for physical insight into the correlation of the roughness spectrum to the forward and backward modal intensities and cross mode coherence. This study applies the Nx2D integral equation coupled-mode approach to 3-D roughness measurements and examines the physics of the coupling of the forward and backward field components and computes the modal intensities as a function of azimuth. The roughness measurements were made in about 20 m of water off Panama City, Florida. [Work supported by ONR Code 322 OA.]