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Published on: September 5, 2018
Acoustic scattering from double-diffusive microstructure.
Andone C Lavery1, Tetjana Ross
1Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. alavery@whoi.edu
The Journal of the Acoustical Society of America
|October 12, 2007
Summary
High-frequency acoustic backscattering effectively measures oceanic double-diffusive microstructure. This technique provides insights into interface thickness and aids in understanding oceanic mixing processes.
Area of Science:
- Oceanography
- Acoustics
- Fluid Dynamics
Background:
- Double-diffusive microstructure, characterized by sharp density and sound speed interfaces, plays a crucial role in oceanic mixing.
- Understanding the dynamics of this microstructure is essential for comprehending large-scale oceanographic processes.
Purpose of the Study:
- To investigate the use of high-frequency broadband acoustic backscattering as a remote-sensing tool for characterizing double-diffusive microstructure.
- To analyze the spectral and temporal characteristics of acoustic echoes from this microstructure.
- To compare acoustic estimates of microstructure parameters with direct measurements.
Main Methods:
- Laboratory measurements of acoustic backscattering (200-600 kHz) from experimentally generated double-diffusive layers.
- Characterization of microstructure using direct sensors and optical shadowgraph techniques.
- Analysis of acoustic echoes in both frequency and time domains, including pulse compression techniques.
- Application of a one-dimensional weak-scattering model.
Main Results:
- Acoustic backscattering measurements revealed significant variability associated with interface oscillations and turbulent plumes.
- Many echoes exhibited distinct spectral structures, providing information on scattering properties.
- Acoustic estimates of interface thickness (1-3 cm) showed good agreement with direct measurements for specific echo types.
- A one-dimensional weak-scattering model provided reasonable predictions of the measured scattering.
Conclusions:
- High-frequency broadband acoustic backscattering is a viable remote-sensing method for mapping oceanic double-diffusive microstructure.
- This technique can provide valuable data on interface thickness and microstructure dynamics.
- Further development could enhance our understanding of double diffusion's contribution to oceanic mixing.
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