Intensity fluctuations from deterministic and random azimuthal variability

• Published in: The Journal of the Acoustical Society of America 2003-10, Vol.114 (4_Supplement), p.2461-2461
• Main Authors: Reilly-Raska, Laurel K., Siegmann, William L., Lynch, James F., Colosi, John A., Duda, Timothy F.
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4779743

Shallow-water sites for shelfbreak PRIMER and ASIAEX show substantial ocean horizontal variability arising from nonlinear internal wave trains. These relatively coherent structures strongly influence acoustic intensity observations, and deterministic propagation modeling has demonstrated their azimuthal effects. Moreover, random variations in the nonlinear internal waves, as well as processes such as linear internal wave fields, contribute to observed intensity fluctuations. Stochastic modeling is performed to show the azimuthal changes induced in the intensity fluctuations. The principal metric of interest is the scintillation index (SI), the ratio of standard deviation to mean intensities. Limiting cases of the SI are examined for examples including both nonlinear internal waves and random ocean variations. Simulations using a three-dimensional parabolic equation model [Collins, J. Acoust. Soc. Am. 94, 2269–2278 (1993)] are discussed, along with an extension of a random modal fluctuation approach [Dozier and Tappert, J. Acoust. Soc. Am. 63, 353–365 (1978)]. [Work supported by ONR.]