Adaptive array invariant in range-dependent environments with variable bathymetry.

Abstract

The adaptive array invariant developed for source-range estimation in shallow water can incorporate the propagation-angle dependence of the waveguide invariant for an ideal waveguide (β=cos2θ) [Byun and Song, J. Acoust. Soc. Am. 148, 925-933 (2020)]. This paper extends the approach to weakly (adiabatic) range-dependent environments with variable bathymetry, wherein the waveguide invariant is a complex function of the bathymetry between source and receiver as well as the propagation angle in powers of sin2θ. For a given bathymetry, the adaptive array invariant can be implemented in an iterative fashion, and its remarkable performance is demonstrated using a short-aperture vertical array (2.8 m) for a broadband source (0.5-3.5 kHz) towed on a continental slope where the water depth varies from 87.5 to 55 m over a 5-km range.