Acoustic reflection from estuarine pycnoclines

Penrose, John D.; Beer, Tom

doi:10.1016/s0302-3524(81)80122-3

Cited by 8 publications

(9 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reflection coefficients can be calculated from a measured profile of any shape and no assumptions about the processes creating the pycnocline need to be made, making Eq. (4) more comprehensive and simpler to implement than the Gupta (1966) and Penrose and Beer (1981) models.…”

Section: Weak-scattering Model For Oceanic Pycnoclinesmentioning

confidence: 99%

“…Pycnoclines are important oceanographically (e.g., Mann and Lazier, 2006), and there is a long history of observations (e.g., Fisher and Squier, 1975;Penrose and Beer, 1981) of enhanced acoustic scattering at mid (1-10 kHz) and high frequencies (>10 kHz) associated with oceanic pycnoclines, defined as gradients in density, but which in the following discussion also refer to the accompanying sound speed gradients. The possibility of scattering from oceanic sound speed gradients was suggested decades ago (Munk and Garrett, 1973) and, around the same time, a scattering model that included sound speed and density gradients was developed (Gupta, 1966).…”

Section: Introductionmentioning

confidence: 99%

“…The possibility of scattering from oceanic sound speed gradients was suggested decades ago (Munk and Garrett, 1973) and, around the same time, a scattering model that included sound speed and density gradients was developed (Gupta, 1966). This scattering model is complex to implement, and applying it to pycnoclines requires making assumptions about the processes giving rise to the pycnoclines (Penrose and Beer, 1981). Penrose and Beer (1981) used it, however, to conclude that scattering at 200 kHz observed at an estuarine salt wedge was due to the pycnocline and not suspended sediments.…”

Section: Introductionmentioning

confidence: 99%

“…This scattering model is complex to implement, and applying it to pycnoclines requires making assumptions about the processes giving rise to the pycnoclines (Penrose and Beer, 1981). Penrose and Beer (1981) used it, however, to conclude that scattering at 200 kHz observed at an estuarine salt wedge was due to the pycnocline and not suspended sediments. More generally it is typically assumed that the observed scattering associated with oceanic pycnoclines is due to passive particulate tracers (Kaye and Anderson, 1979), such as zooplankton or suspended sediments.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Acoustic scattering from density and sound speed gradients: Modeling of oceanic pycnoclines

Ross

Lavery

2011

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

A weak-scattering model that allows prediction of acoustic scattering from oceanic pycnoclines (and the accompanying sound speed gradients) based on hydrographic profiles is described. Model predictions, based on profiles from four locations, indicate that scattering from oceanic pycnoclines is measurable using standard scientific sonars operating at frequencies up to 200 kHz but generally only for pycnocline thicknesses less than 10 m. Accurate scattering models are key to assessing whether acoustic remote sensing can be used to map oceanic pycnoclines and for determining whether scattering from pycnoclines needs to be taken into account when estimating, for instance, zooplankton abundance from acoustic data.

show abstract

Section: Weak-scattering Model For Oceanic Pycnoclinesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Acoustic scattering from density and sound speed gradients: Modeling of oceanic pycnoclines

Ross

Lavery

2011

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

show abstract

“…The physical environment itself can also be examined acoustically. The target strength of pycnoclines can be measured by acoustic reflection and may have a target strength of -75 to -85 dB at 200 kHz [6]. Internal waves and their fine structure have been measured by acoustic methods [7,8].…”

mentioning

confidence: 99%

Measurements of sound scattering as a means of examining ecological interactions between marine organisms and their environment

Macaulay

Proceedings of OCEANS '93

View full text Add to dashboard Cite

Abshacf -Significant advances in hydroacoustic systems have occurred in recent years and the availability and application of such systems has greatly improved the quality of quantitative sound scattering measurements from towed and moored sensors. There remain questions of relating the quantity of sound scatter observed (a highly precise measurement) to the quantity of biota or other material causing reflections or volume reverberation (a less well understood process, where behavior of the ensonified organisms causes variation in their target strength). Measurements of sound scattering coupled to directed sampling of target organisms (using nets or video) frequently reveals many aspects of interactions between organisms and their environment. This paper presents methods and examples of measurements and comparisons between sound scatter, causative organisms, and environmental data. INTKODUCTIONThe specifics of echo integration of hydroacoustic data have been well described [ 13. The author has developed and used the system described here for a number of one week to o n e month surveys in a diversity of environments (the Antarctic, Georges Bank off Cape Cod, Hood Canal in Puget Sound, Jervis Inlet in British Columbia). In each of these cases, large quantities of data were collected and analyzed in real time and results placed in the database system to permit further analyses and production of data products. Results of these surveys are reported elsewhere [2-41 and they incorporate many of the data products described in this paper. DATA PROCESSINGDuring field operations, some or all of the available acoustic data may be recorded in digital format (e.g. using a digital audio tape system or similar format) for detailed post-survey re-analysis or to provide for collection and analysis of a second simultaneously collected frequency. The data collection system provides visual displays of the incoming data in several formats, these include paper chart records, oscilloscope signals and color scaled video display of integrated echo intensity for both ping by ping data and the integration interval. Periodic transfer of data files to a second computer, permits summarization and visualization of data collection by means of graphic and printed output, including color echograms.Other analyses may be performed in the field or as a postsurvey activity. This method of data analysis provides timely production of data items of assistance in field work (e.g. sampling depths for nets) and makes a complete analysis of results available for examination immediately following a survey.Many of the details of this process are described in [5]. The use of color coded displays of the data as echograms or other graphical plots, provides a means of rapidly assessing regions of interest and sections of data which may of special interest. The large volume of hydroacoustic data precludes dfective assessment of features within a data set by examination of numerical data alone. For example, a screen of color coded pixels 640 by 480 can be used to rep...

show abstract