A low-noise conductivity microstructure instrument

Meagher, T.; Pederson, A.; Gregg, Michael C.

doi:10.1109/oceans.1982.1151743

Cited by 10 publications

(2 citation statements)

References 6 publications

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“…[25] The SBE-7 has a sensor response of −3 dB at 100 cycles m −1 (cpm) and an electronics response of −3 dB at 1000 cpm [Meagher et al, 1982]. For our purposes, the transfer function is then:…”

Section: Microstructure Measurementsmentioning

confidence: 99%

Internal tidal beams and mixing near Monterey Bay

Johnston¹,

Rudnick²,

Carter³

et al. 2011

J. Geophys. Res.

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[1] The spatial structure of velocity, density, and mixing in an internal tidal beam generated at a submarine ridge near Monterey Bay was observed using a combination of vessel-mounted acoustic Doppler current profilers, a towed conductivity-temperaturedepth instrument (SeaSoar), and microconductivity sensors mounted on SeaSoar. Three <60 km meridional sections from the surface to 400-670 m in depth were occupied a total of 56 times during 16 days with the sampling pattern detuned from the M 2 tide. Averaging over all observations at a given latitude-depth bin produces a phase average of the M 2 internal tide. Observed velocity and displacement variances are scaled to estimate energy density. A beam in energy density originates from a submarine ridge and reflects with diminished amplitude at the surface. These results compare favorably with a numerical tidal model. The upward and downward beams show modestly elevated turbulence, which is patchy along the beam and has mean values about 50% larger than those outside of the beam. Peak values can be almost an order of magnitude larger in the beam. Dissipation increases with increasing shear and stratification similar to the MacKinnon-Gregg parameterization. Intermediate nepheloid layers were found in over half of the meridional sections. Their phasing and direction indicate that they originate at a secondary, weaker internal tidal generation site found in the model but not in the observations presumably due to mesoscale variability affecting stratification at the generation site and during wave propagation. The offshore movement of sediment is a result of westward mean current and internal wave-driven transport.

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Section: Microstructure Measurementsmentioning

confidence: 99%

Internal tidal beams and mixing near Monterey Bay

Johnston¹,

Rudnick²,

Carter³

et al. 2011

J. Geophys. Res.

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“…The SBE 7 sensor had two forward directed platinized electrodes. A comparable sensor is described by Meagher et al [1982]. The sensor output is preemphasized to increase signal‐to‐noise ratio at high frequencies.…”

Section: Instruments and Data Collectionmentioning

confidence: 99%

Systematic microstructure variability in double‐diffusively stable coastal waters of nonuniform density gradient

Duda

Rehmann

2002

J. Geophys. Res.

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[1] Conductivity microstructure, water velocity, and stratification were measured during a tow-yo transect near the New England shelf/slope front in early August 1997. Velocity data were collected with an acoustic Doppler profiler on the ship. The other data were collected with a towed platform. Estimates of c, the rate of dissipation of temperature variance, were computed from the conductivity data with vertical resolution of 0.3 m. Relationships between c and shear, temperature gradient, buoyancy frequency (N), and gradient Richardson number (Ri) were explored, with special focus on measurements taken in waters stable to double-diffusive processes (to avoid ambiguity of interpretation) and exhibiting variable density gradient (N ranging from 5 to 40 cph). For this subset of data, c computed from data grouped into classes of local mean temperature gradient (d " T/dz) was proportional to d " T/dz to the 0.7 power, which is consistent with diapycnal thermal eddy diffusivity K being proportional to (d " T /dz) À1.3 within the framework of the Osborn-Cox model that relates c and the mean temperature gradient to the heat flux. No correlation between K and Ri was observed, with Ri computed at 4 m vertical scale, so that systematic inhomogeneous largescale forcing is not responsible for a false correlation of K and d " T/dz. Water mass salinity characteristics in the area caused N 2 to be proportional to (d " T/dz)4/5 , rather than to d " T /dz as in the isohaline case, giving rise to the steep inverse relation K = 10 À10 N À3.3 , with N in radians/ s and diffusivity in m 2 /s. The fit K = 2 Â 10 À9 N À2.5 results if one questionable data ensemble is disregarded. These relations are comparable to results obtained previously from the nearbottom tow data. They are not intended to be universal formulae but are meant to describe the conditions we encountered. They are not expected to hold at high and low values of N outside of our measurement range. An interpretation is that under these conditions the less strongly stratified (lower N) layers in this shelf area are more prone to instability of the larger-scale shear than the intervening interfaces, with the subsequent greater energy dissipation in the layers leading to higher buoyancy flux KN 2 in the layers than in the interfaces.

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Contamination of conductivity measurements by waterborne particles

Okawa

Dugan

1984

Ocean Engineering

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A low-noise conductivity microstructure instrument

Cited by 10 publications

References 6 publications

Internal tidal beams and mixing near Monterey Bay

Internal tidal beams and mixing near Monterey Bay

Systematic microstructure variability in double‐diffusively stable coastal waters of nonuniform density gradient

Contamination of conductivity measurements by waterborne particles

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