Ocean acoustic tomography based on adiabatic mode theory

A new method of ocean acoustic tomography is developed on the basis of adiabatic normal-mode theory. It is a full-wave method suitable for low frequency in a slowly varying range-dependent waveguide. The modal phase difference perturbations are proposed as data for inverting the sound-speed profile perturbation for a continuous-wave (cw) source. The modal travel time perturbations are proposed as data for a pulse source. It is shown that the ‘‘normalized depth structure,’’ as well as the ‘‘range-averaged strength parameter’’ (defined as the product of the effective horizontal scale and the maximum sound-speed perturbation), can be retrieved from the vertical slice modal tomography. A simulation example of inversion is presented to verify the basic ideas.