Robert A. Coury
William L. Siegmann
Rensselaer Polytechnic Inst., Troy, NY 12180-3590
Michael D. Collins
Naval Res. Lab., Washington, DC 20375
The parabolic equation (PE) method has proven to be an efficient method for solving range-dependent ocean acoustics problems. Recently an extension has been made to handle two-dimensional waveguides of varying thickness. This type of modeling is necessary when the upper boundary of the waveguide is allowed to change, as for example in propagation up a beach or in an ocean with a gradually undulating surface. The adiabatic mode PE is another extension that has been developed to solve global scale, three-dimensional propagation problems. In this paper, the three-dimensional adiabatic mode PE is extended to handle problems involving a gradual range dependence in the overall thickness of the waveguide. The modified adiabatic PE has several applications. On relatively small scales, it may be applied to solve three-dimensional beach acoustics problems or to model diffraction by an island. It may also be applied to solve global-scale seismoacoustic problems in which topography on the continents plays a significant role. [Work supported by ONR.]