A uniformly valid solution for acoustic normal mode propagation in a range varying ocean

Abstract

It is shown that the adiabatic approximation usually presented in the literature for acoustic normal mode propagation in a range-dependent ocean has serious limitations and breaks down at rather short ranges. This is because the approximation does not account properly for the phase of the modes. A rigorous, uniformly valid asymptotic expansion is presented which provides a solution with greatly improved range of validity.