Dynamic Response Calibration of Sea-Bird Temperature and Conductivity Probes

Gregg, Michael C.; Hess, William C.

doi:10.1175/1520-0426(1985)002<0304:drcosb>2.0.co;2

Cited by 26 publications

(10 citation statements)

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“…This has been shown by many prior investigations to be mainly due to misalignment of the temperature and conductivity measurements due to physical separation of the thermistor and the conductivity cell, as well as to mismatches between the response times of the two sensors (Horne and Toole 1980;Gregg and Hess 1985). With pumped CTD systems such as the commonly used SBE 911, where the flow through the T/C duct is constant, the proper alignment is easily achieved by advancing conductivity in time by a fixed amount.…”

Section: Introductionmentioning

confidence: 99%

Processing of Underway CTD Data

Ullman

Hebert

2014

Journal of Atmospheric and Oceanic Technology

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A processing methodology for computation of accurate salinity from measurements with an underway CTD (UCTD) is presented. The UCTD is a rapidly profiling sensor package lacking a pump that relies on instrument motion to produce flow through the conductivity cell. With variable instrument descent rate, the flow through the cell is not constant, and this has important implications for the processing. As expected, the misalignment of the raw temperature and conductivity is found to be a function of the instrument descent rate. Application of a constant temporal advance of conductivity or temperature as is done with pumped CTDs is shown to produce unacceptable salinity spiking. With the descent rate of the UCTD reaching upwards of 4 dbar s 21 , the effect of viscous heating of the thermistor is shown to produce a significant salinity error of up to 0.005 psu, and a correction based on previous laboratory work is applied. Correction of the error due to the thermal mass of the conductivity cell is achieved using a previously developed methodology with the correction parameters varying with instrument descent rate. Comparison of salinity from the UCTD with that from a standard shipboard, pumped CTD in side-by-side deployments indicates that the processed UCTD salinity is accurate to better than 0.01 psu.

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Section: Introductionmentioning

confidence: 99%

Processing of Underway CTD Data

Ullman

Hebert

2014

Journal of Atmospheric and Oceanic Technology

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“…Temperature is measured with a pressure-protected, fast-response thermistor mounted near the duct intake, while conductivity is sensed inside a long, narrow, three-electrode cell located downstream of the intake. Accurate salinity data requires corrections for temporal and spatial mismatches in these sensor responses (Fofonoff et al 1974;Gregg and Hess 1985;Lueck 1990;Lueck and Picklo 1990;Morison et al 1994).…”

Section: Introductionmentioning

confidence: 99%

Sensor Corrections for Sea-Bird SBE-41CP and SBE-41 CTDs

Johnson

Toole

Larson

2007

J. Atmos. Oceanic Technol.

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Sensor response corrections for two models of Sea-Bird Electronics, Inc., conductivity-temperaturedepth (CTD) instruments (the SBE-41CP and SBE-41) designed for low-energy profiling applications were estimated and applied to oceanographic data. Three SBE-41CP CTDs mounted on prototype ice-tethered profilers deployed in the Arctic Ocean sampled diffusive thermohaline staircases and telemetered data to shore at their full 1-Hz resolution. Estimations of and corrections for finite thermistor time response, time shifts between when a parcel of water was sampled by the thermistor and when it was sampled by the conductivity cell, and the errors in salinity induced by the thermal inertia of the conductivity cell are developed with these data. In addition, thousands of profiles from Argo profiling floats equipped with SBE-41 CTDs were screened to select examples where thermally well-mixed surface layers overlaid strong thermoclines for which standard processing often yields spuriously fresh salinity estimates. Hundreds of profiles so identified are used to estimate and correct for the conductivity cell thermal mass error in SBE-41 CTDs.

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“…The exhaust of the pumped duct is at the same (pressure) level as the intake, so as to eliminate the ram effect of dynamic pressure (Sea-Bird, 2012). Thus, in theory the flow speed is constant past the sensors, which simplifies the dynamic response calibration (Gregg and Hess, 1985) by eliminating errors in T-measurement due to sensor-friction (≈ +110 -3 °C for a 1 m s -1 flow speed; Larson and Pedersen, 1996) and weaker errors due to flow-induced pressure variations in an adiabatic lapse rate environment (p d = 1/2ρU 2 , ρ the water density; for a speed range of U = [0, 4.5] m s -1 this yields a pressure range of [0, 1] dbar).…”

Section: Datamentioning

confidence: 99%

Ship motion effects in CTD-data from weakly stratified waters of the Puerto Rico trench

Haren

2015

Deep Sea Research Part I: Oceanographic Research Papers

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Dynamic Response Calibration of Sea-Bird Temperature and Conductivity Probes

Cited by 26 publications

References 0 publications

Processing of Underway CTD Data

Processing of Underway CTD Data

Sensor Corrections for Sea-Bird SBE-41CP and SBE-41 CTDs

Ship motion effects in CTD-data from weakly stratified waters of the Puerto Rico trench

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