Relative Importance of Bottom Attenuation and Scattering in the Shallow-Water TREX13 Environment

In this paper, the results of applying normal mode models to explain measured data collected during the 2013 Target and Reverberation Experiment (TREX13) are presented. An adiabatic, and one-way coupled, Born approximation normal mode model (Nautreverb) and an energy conserving two-way coupled mode model (Aeneid) are described. Both monostatic and bistatic reverberation time series solutions are produced with the models for a rough bottom spectrum or a realization from it. Next, monostatic reverberation time series are produced, for both the Nautreverb and Aeneid models, with the measured bottom roughness parameter values obtained from measurements made during TREX13. In addition, loss mechanisms for depth averaged transmission loss are assessed. The relative effects of bottom attenuation and loss due to scattering, for several variants of the model parameters for the TREX13 environment, are also discussed. Based on the small roughness measured at the TREX13 site, bottom attenuation appears to be the dominant loss mechanism. Adjustments of the frequency dependence of the bottom attenuation were constructed to reproduce salient features of the measured transmission loss.