The effects of environmental variability and spatial sampling on the three-dimensional inversion problem

Abstract

The overall goal of this work is to quantify the effects of environmental variability and spatial sampling on the accuracy and uncertainty of estimates of the three-dimensional ocean sound-speed field. In this work, ocean sound speed estimates are obtained with acoustic data measured by a sparse autonomous observing system using a perturbative inversion scheme [Rajan, Lynch, and Frisk, J. Acoust. Soc. Am. 82, 998-1017 (1987)]. The vertical and horizontal resolution of the solution depends on the bandwidth of acoustic data and on the quantity of sources and receivers, respectively. Thus, for a simple, range-independent ocean sound speed profile, a single source-receiver pair is sufficient to estimate the water-column sound-speed field. On the other hand, an environment with significant variability may not be fully characterized by a large number of sources and receivers, resulting in uncertainty in the solution. This work explores the interrelated effects of environmental variability and spatial sampling on the accuracy and uncertainty of the inversion solution though a set of case studies. Synthetic data representative of the ocean variability on the New Jersey shelf are used.

Variability of phase and amplitude fronts due to horizontal refraction in shallow water

“…Subsequently, the following phenomena were studied: focusing/defocusing of the sound field in the horizontal plane in the presence of nonlinear internal waves Badiey et al, 2005); variations of the interference pattern in the horizontal plane in the area of a coastal wedge in (Deane and Buckingham, 1993;Katsnelson et al, 2013), or in the area of the underwater canyon in (Duda et al, 2011;Y.-T. Lin, 2013); multipath propagation in the horizontal plane in an experiment in the Florida Strait (Heaney and Murray, 2009); and many others. In the papers (Bender et al, 2014;Ballard et al, 2012), the importance of taking horizontal refraction into account for inverse problems was discussed as well.…”