Velocity Imprecision in Finite-Beamwidth Shipboard Doppler Sonar: A First-Generation Correction Algorithm

Pinkel, Robert

doi:10.1175/jtech-d-12-00041.1

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…Ocean currents described here were primarily measured with the Hydrographic Doppler Sonar System (HDSS). HDSS consists of a 140‐ and a 50‐kHz Doppler sonar with ranges of 250 and 1,000 m, respectively (Pinkel, ). For this analysis, velocity from the two sonars was merged and gridded into 1‐min bins.…”

Section: Methodsmentioning

confidence: 99%

Eddy Wake Generation From Broadband Currents Near Palau

et al. 2019

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Wake eddies are frequently created by flow separation where ocean currents encounter abrupt topography in the form of islands or headlands. Most previous work has concentrated on wake eddy generation by either purely oscillatory (usually tidal) currents, or quasi‐steady mean flows. Here we report measurements near the point of flow separation at the northern end of the Palau island chain, where energetic tides and vertically sheared low‐frequency flows are both present. Energetic turbulence measured near the very steeply sloping ocean floor varied cubically with the total flow speed (primarily tidal). The estimated turbulent viscosity suggests a regime of flow separation and eddying wake generation for flows that directly feel this drag. Small‐scale (∼1 km), vertically sheared wake eddies of different vorticity signs were observed with a shipboard survey on both sides of the separation point, and significantly evolved over several tidal periods. The net production and export of vorticity into the wake, expected to sensitively depend on the interplay of tidal and low‐frequency currents, is explored here with a simple conceptual model. Application of the model to a 10‐month mooring record suggests that inclusion of high frequency oscillatory currents may boost the net flux of vorticity into the ocean interior by a depth dependent factor of 2 to 25. Models that do not represent the effect of these high frequency currents may not accurately infer the net momentum or energy losses felt where strong flows encounter steep island or headland topography.

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Section: Methodsmentioning

confidence: 99%

Eddy Wake Generation From Broadband Currents Near Palau

et al. 2019

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“…1) and are not used in subsequent calculations as vertical profiles are no longer available. Observations from the Arctic Ocean, which has a different internal wave regime (Levine et al 1987;D'Asaro and Morehead 1991;Wijesekera et al 1993;Pinkel 2005) and occupies a small volume of the World Ocean, are not considered.…”

Section: Datamentioning

confidence: 99%

Global Patterns of Diapycnal Mixing from Measurements of the Turbulent Dissipation Rate

Waterhouse

MacKinnon

Nash

et al. 2014

Journal of Physical Oceanography

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448

467

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The authors present inferences of diapycnal diffusivity from a compilation of over 5200 microstructure profiles. As microstructure observations are sparse, these are supplemented with indirect measurements of mixing obtained from (i) Thorpe-scale overturns from moored profilers, a finescale parameterization applied to (ii) shipboard observations of upper-ocean shear, (iii) strain as measured by profiling floats, and (iv) shear and strain from full-depth lowered acoustic Doppler current profilers (LADCP) and CTD profiles. Vertical profiles of the turbulent dissipation rate are bottom enhanced over rough topography and abrupt, isolated ridges. The geography of depth-integrated dissipation rate shows spatial variability related to internal wave generation, suggesting one direct energy pathway to turbulence. The global-averaged diapycnal diffusivity below 1000-m depth is O(10 . The compiled microstructure observations sample a wide range of internal wave power inputs and topographic roughness, providing a dataset with which to estimate a representative global-averaged dissipation rate and diffusivity. However, there is strong regional variability in the ratio between local internal wave generation and local dissipation. In some regions, the depthintegrated dissipation rate is comparable to the estimated power input into the local internal wave field. In a few cases, more internal wave power is dissipated than locally generated, suggesting remote internal wave sources. However, at most locations the total power lost through turbulent dissipation is less than the input into the local internal wave field. This suggests dissipation elsewhere, such as continental margins.

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“…Mesoscale current patterns were observed over a wide area during a four-day survey on R/V Roger Revelle in October 2015. Currents were measured with the ship's Hydrographic Doppler Sonar System (Pinkel, 2012), while density was measured using SeaSoar, a towed vehicle equipped with a CTD. During this period of eastward flow, the upstream Ro is about 0.5, but in the wake, Ro increases eddies of different vorticity signs, and strengths, on either side of the point.…”

Section: Nec Neccmentioning

confidence: 99%