Theoretical Study of the Propagation of Infrasonic Waves in the Atmosphere. Extension of the Method of Normal Modes to Wave Propagation in an Almost-Stratified Medium

摘要

A theory is presented which permits the extension of the method of normal modes to guided wave propagation in a medium with properties varying slowly with horizontal coordinates in addition to varying with the vertical coordinate. The principal assumption of the neglect of coupling between normal modes is justified as long as the horizontal wave numbers of different modes are not too closely spaced. It is predicted that different frequencies in different modes follow different horizontal paths. A ray tracing method is described for computing these paths. The theory is then applied to the study of the dispersion of waves from an explosive source in shallow water with slowly varying depth. (Author)