Bjerrum-Niese, Christian

Jensen, Leif Bjørnø

Christian Bjerrum‐Niese

Leif Bjo/rno/

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Influence of statistical surface models on dynamic scattering of high‐frequency signals from the ocean surface

Temporal variations of scattering of high-frequency, monochromatic signals from the ocean surface has been studied numerically. In the high-frequency domain the dynamic scattering can be modeled by a coherence function of the scattered pressure field, which is based on the Kirchhoff integral; the surface roughness is described by a spatial surface spectrum and the surface motion is described by the gravity-wave dispersion relation [D. Dowling and D. Jackson, J. Acoust. Soc. Am. 93, 3149–3157 (1993)]. Applying some modifications to this approach, the temporal coherence function is found by numerical evaluation of a double integral. The time-varying scattering can be examined in the frequency domain by the power spectrum (the Fourier transform of the coherence function). It is examined how a monochromatic signal is shifted and smeared in the frequency domain by comparing computations for the Pierson–Moskowitz spectrum (for a fully developed sea) with computations for the JONSWAP spectrum (for fetch-limited seas). The following results, among other issues, have been obtained: As the fetch decreases, the surface waves become shorter, leading to increasing frequency shifting of the scattered signal. [Work sponsored by the Danish Technical Research Council and the EU/MAST programme.

Online Research Database In Technology

Influence of statistical surface models on dynamic scattering of high-frequency signals from the ocean surface (A)

http://orbit.dtu.dk/ws/files/4415207/Jensen.pdf

Influence of statistical surface models on dynamic scattering of high-frequency signals from the ocean surface (A)

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Online Research Database In Technology