Microstructure Sources of Sound Backscattering in a Stratified Flow

摘要

Investigation of sound-scattering mechanisms is of key importance in the development of adequate algorithms for remote diagnostics of the ocean. According to modern concepts, the basic mechanism responsible for the generation of scattering inhomogeneities is assumed to be a turbulent microstructure with an intrinsic scale on the order of the sound wavelength λ. In this case, maximum scattering intensity is expressed in terms of the spectral fluctuation density of sound speed, which is taken at the doubled wavenumber 2k_0 = 4π/λ of the incident sound wave [1-3]. Since natural stratified flows are known to be inhomogeneous in depth, such a regularity must be valid only at certain horizons in which there exists the developed turbulence. However, from the data of full-scale tests performed in ocean, it follows that the vertical cross-section profiles of scattering strongly correlate with the spectral density of temperature fluctuations in the entire range of probed depths [4, 5]. This implies that the mechanism underlying the formation of the sound-scattering microstructure may be of non-turbulent origin.