Acoustic Backscatter from Turbulent Microstructure

Seim, Harvey; Gregg, Michael C.; Miyamoto, Robert T.

doi:10.1175/1520-0426(1995)012<0367:abftm>2.0.co;2

“…More recently, there has also been significant effort directed towards the quantitative use of narrowband acoustic scattering techniques for investigating small-scale physical processes, such as oceanic microstructure (e.g. Goodman, 1990;Seim et al, 1995;Lavery et al, 2003;Ross and Lueck, 2003;Warren et al, 2003). Acoustic scattering techniques provide a rapid, high-resolution, synoptic, remote sensing alternative to more traditional sampling strategies.…”

Section: Approachmentioning

confidence: 99%

Continued Analysis of High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves during SW06

Lavery¹

2010

0

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LONG-TERM GOALSTo understand high-frequency broadband acoustic backscattering from small-scale physical processes, such as internal waves, turbulence, and microstructure, in shallow, stratified waters. OBJECTIVESThe primary objective of the overall research program was to measure high-frequency broadband acoustic backscattering in highly stratified, energetic environments and to determine the contribution to scattering from temperature and salinity microstructure. Testing the validity of existing scattering models and the initial development of new, and/or extensions of existing, simple physics-based scattering models was a secondary objective of this work.To accomplish the stated objectives, high-frequency broadband (150-600 kHz) acoustic backscattering measurements were performed during the generation, propagation, and dissipation of non-linear internal waves in August 2006 as a part of the SW06/NLIWI experiment. Almost coincident microstructure measurements were collected by Jim Moum with a profiling microstructure instrument, Chameleon. The contribution to scattering from biological organisms was quantified using netsamples, from which the zooplankton taxa, size, and depth (in coarse vertical bins) can be determined.Analysis of these data to date has focused on (1) determining the dominant scattering mechanisms giving rise to enhanced backscattering often associated with the passage of non-linear internal waves, with particular attention given to elevated scattering associated to Kelvin-Helmholtz instabilities, and (2) inverting the broadband scattering data for meaningful biological and physical parameters and comparing the acoustically-inferred to directly measured parameters, thereby allowing the validity of the scattering models to be tested.The primary objectives of the effort described here are: 1) to understanding and quantifying the contribution to acoustic backscattering from the seasonal pycnocline, 2) to investigate the statistics

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“…More recently, there has also been significant effort directed towards the quantitative use of narrowband acoustic scattering techniques for investigating small-scale physical processes, such as oceanic microstructure (e.g. Goodman, 1990;Seim et al 1995; 2003; Ross and Lueck, 2003;Warren et al, 2003). Acoustic scattering techniques provide a rapid, highresolution, synoptic, remote sensing alternative to more traditional sampling strategies.…”

Section: Approachmentioning

confidence: 99%

Analysis of High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves During SW06

Lavery

¹

2009

0

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LONG-TERM GOALSTo understand high-frequency broadband acoustic backscattering from small-scale physical processes, such as internal waves, turbulence, and microstructure, in shallow, stratified coastal waters. OBJECTIVESThe primary objective of the proposed research was to measure high-frequency broadband acoustic backscattering in highly stratified, energetic environments and to determine the contribution to scattering from temperature and salinity microstructure. Testing the validity of existing scattering models and the initial development of new, and/or extension of existing, simple physics-based scattering models was a secondary objective of this work.To accomplish the stated objectives, high-frequency broadband (150-600 kHz) acoustic backscattering measurements were performed during the generation, propagation, and dissipation of non-linear internal waves in August 2006 as a part of the SW06/NLIWI experiment. Almost coincident microstructure measurements were collected by Jim Moum with a profiling microstructure instrument, Chameleon. The contribution to scattering from biological organisms was quantified using a multiple-opening and closing net and environmental sensing system (MOCNESS), from which the zooplankton taxa, size, and depth (in coarse vertical bins) can be determined. The particular effort described here focuses on the analysis on these data.

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“…Salt fingers or diffusion can provide the variations in microstructure without the presence of turbulence. While the volume scattering strength has been estimated from microstructure measurements made by profiling instruments (Seim et at., 1995;Seim, 1999), until this work there has not been a study relating the acoustic scattering to both the biology and microstructure present.…”

Section: Microstructurementioning

confidence: 99%

Estimating Gulf of Maine zooplankton distributions using multiple frequency acoustic, video and environmental data

Warren¹

2001

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This thesis develops methods useful for estimating zooplankton distributions in the field by combining acoustic models and an integrated set of field data. The accnracy of existing models for fluid-like and elastic-shelled animals is determined by analysis of scattering data from individual aninials in a laboratory tank. Results indicate that simple two-ray scattering rnodels are accurate and allow predictions of size or orientation of an animal to be made for certain animal orientations. A model for gas-bearing zooplankton is compared with in sit'l multiple frequency acoustic measurements from siphonophores. Estimates of the numerical density of these animals are made using echo integration data from a scientific echo-sounder. Multiple frequency acoustic scattering data from a survey of an internal wave are analyzed to determine the contributions from biologieal and physical sources. Net tow data provide information about biological scatterers while temperature and salinity profiles are used with a theoretical model to predict contributions from physical sources. Results indicate that scattering from physical sources is comparable to that from biological sources in certain regions and that spectra may be used to distinguish these sources. Improved estimates of biomass from acoustic scatteriug data were made by accounting for the scattering contributions from physical sources. This is the first work to quantify the scattering contributions from biological and physical sources of scattering in a field study. It is better to fail in originality than to succeed in iniitation. He who has never failed somewhere, that man cannot be great. If it be said that continual snccess is proof that a man wisely knows his powers, it is only to be added that, in that ease, he knows them to be smaIL Hennan MelvilleDon't believe the hype. That ¡nade the school a place of decent order vVhere books were read and sums were proven true And paper maps t.hat showed t.he land and water vVere held up as the real wide world to you. Always, he kept his eyes upon his books:And now he has grown to be a man fellow .II' classmates are an exceptional group of people, not to mention they're all wicked srnart.From the initial pot-lucks to the defense parties, it's been a fantastic group of people t.o have as my peers.Ann P. was always up for a "date". Liz K. survived 10 hours in a ear with me and didn't have to be institutionalized. Sheri \V. never tackled me too hard while playing rugby. Brenda J. attended Lollapalooza 5 with me. Nicole P. survived with me during our thesis writing. i'ike A. reminded me you're never too old to have fun. 'rom i'd., Lou StL., and l'like B. were the original members of VomeletLe. Suzie \V.enthusiasm for school was a contrast to mine. Fellow NRQ members ,Albert and i'ak, made the last 6 months of school very survivable. Doc Reddy made the best brunclics I've ever eaten, taught me many acronyms, was a co-founder of PNF and rescued me after my kayak was attacked a rogue buoy.

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Acoustic Backscatter from Turbulent Microstructure

Cited by 85 publications

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Continued Analysis of High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves during SW06

Continued Analysis of High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves during SW06

Analysis of High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves During SW06

Estimating Gulf of Maine zooplankton distributions using multiple frequency acoustic, video and environmental data

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