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    Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations : shallow-water environments

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    JAS001749.pdf (3.182Mb)
    Date
    2012-02
    Author
    Colosi, John A.  Concept link
    Duda, Timothy F.  Concept link
    Morozov, Andrey K.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/5091
    As published
    https://doi.org/10.1121/1.3666002
    DOI
    10.1121/1.3666002
    Keyword
     Monte Carlo methods; Perturbation techniques; Seawater; Short-range order; Statistics; Underwater acoustic propagation 
    Abstract
    Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.
    Description
    Author Posting. © Acoustical Society 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1749-1761, doi:10.1121/1.3666002.
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    • Applied Ocean Physics and Engineering (AOP&E)
    Suggested Citation
    Journal of the Acoustical Society of America 131 (2012): 1749-1761
     

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