A 2-DIMENSIONAL DOWNSLOPE PROPAGATION MODEL BASED ON COUPLED WEDGE MODES

A "wedge-mode" representation of the acoustic field has been implemented in a two-dimensional downslope 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 Eastern Mediterranean in winter and summer. For an isospeed profile over a penetrable bottom, coupling between the wedge modes is negligible. For a realistic depth-dependent profile, however, the mode coupling is significant and cannot be neglected. When mode coupling is accounted for, good agreement is obtained with the PE results. The wedge-mode calculation is considerably faster than the reference PE calculation. On a general-purpose workstation, for example, a typical wedge-mode calculation required 10 min while the corresponding finite-difference PE calculation required 8.5 h. As with all mode calculations, the wedge-mode computation is straightforward to implement on a parallel computer. Using off-the-shelf parallel processors ("transputers") and a personal computer, the parallel calculation is as fast as the sequential calculation on a general-purpose workstation. Hence it appears possible to do significant calculations in the field using a personal computer configured with parallel processors.