High frequency quasi-normal waves for nonstationary deep-water waveguide

The propagation of nonharmonic acoustic waves in ocean refractive waveguide with slowly varying properties in horizontal directions and time is treated. The waveguide is modulated as water layer with plane boundaries. The wavelength is assumed to be small in comparison with the width of the layer. A set of asymptotic solutions of the wave equation called as quasi-normal waves is constructed. Our approach extends the applicability region of the well known method of normal waves when the adiabatic expansion failed. A unified formal procedure for construction of the quasi-normal waves is proposed.