Accession Number : ADA187837

Title :   Estimation of Sea Surface Wave Spectra Using Acoustic Tomography.

Descriptive Note : Doctoral thesis,

Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA

Personal Author(s) : Miller, James H

PDF Url : ADA187837

Report Date : Sep 1987

Pagination or Media Count : 176

Abstract : This thesis develops a new technique for estimating quasi-homogeneous and quasi-stationary sea surface wave frequency-direction spectra using acoustic tomography. The analysis of acoustic (mode and ray) phase and travel time perturbations due to a rough sea surface is presented. Two canonical waveguides (ideal shallow water and linear squared index of refraction) are used as examples for the mode perturbation. The analysis is used to explain high mode coherence measured in the FRAM IV experiment. The forward problem of computing the acoustic phase and travel time perturbation spectra given the surface wave spectrum is solved to first order. An application of the technique to ray phase data taken during the MIZEX '84 experiment is shown. The inverse problems for the homogeneous and quasi-homogeneous frequency-direction spectrum are introduced. The theory is applied to synthetic data which simulate a fetch-dependent sea. The estimates made agree well with the 'actual' (synthetic data) spectrum. The effect of noise in the travel time estimates is studied. The sensitivity of the technique to the number of rays used in the inversion is investigated and the resolution and variance of the inverse method are addressed. Keywords: Acoustic scattering; Ocean waves; Acoustic tomography.

Descriptors :   *ACOUSTIC SCATTERING, *OCEAN WAVES, *SURFACE WAVES, *TOMOGRAPHY, *ACOUSTIC DETECTION, ACOUSTICS, ESTIMATES, INVERSION, OCEAN SURFACE, PERTURBATIONS, REFRACTION, SHALLOW WATER, SPECTRA, SURFACE ROUGHNESS, THESES, TRAVEL TIME, WAVEGUIDES, REFRACTIVE INDEX, GRAPHS

Subject Categories : Physical and Dynamic Oceanography
      Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE