James C. Preisig
Timothy F. Duda
Appl. Ocean Phys. and Eng. Dept., Woods Hole Oceanogr. Inst., Woods Hole, MA 02543
Acoustic propagation through a continental-shelf waveguide containing
internal solitary waves has been modeled with the finite-element parabolic
equation (FEPE). The waveguide has two essentially mixed layers separated by a
gradient layer, with a homogeneous, lossy bottom. Solitary waves (pycnocline
depressions) of many sizes and shapes are included, not all of which fit the
dispersion relation. Including both physical and unphysical waves aids
interpretation of the forward-scattering (mode coupling) mechanism. Solitary
waves of horizontal scale length 50 to 150 m cause significant mode coupling.
Longer and shorter solitons give weaker coupling. For cw signals (400 Hz), the
results of a sudden approximation model for a single soliton are compared to
those generated with the FEPE model and provide some insight into the mode
coupling behavior. The results for a broadband pulse (e.g.,