A two-dimensional downslope propagation model based on coupled wedge modes

Abstract

A “wedge-mode” representation of the acoustic field [M. J. Buckingham, J. Acoust. Soc. Am. 82, 198–210 (1987)] has been implemented in a 2-D propagation model that can treat realistic sound-speed profiles. Wedge-mode calculations are compared to parabolic equation (PE) calculations for an isospeed profile and profiles typical of the Mediterranean sea in summer and winter. For an isospeed profile over a penetrable bottom, the wedge modes are almost uncoupled. For a realistic depth-dependent profile, however, the modes are significantly coupled. Moreover, at the beginning of the downslope region, mode-continuum-mode coupling (tunneling) occurs. When only the wedge-mode coupling is accounted for, fair agreement is obtained with the parabolic equation results. When, in addition, the tunneling effect is accounted for with a hybrid mode-PE model, excellent agreement is obtained with the full parabolic equation calculation.