<div><p>CTD profiles at the Hydrostation S site have been collected since station #643 in October 1988 and although there have been some changes during the past thirty-two years as a result of new instrumentation or methodologies, the general sampling procedures have been consistent with those detailed in the BATS method manual version # 4 (Knap et al., 1997).</p>
<p>In summary, the CTD is operated as per SeaBird's suggested methods with data collection at the full scan rate of 24 Hz. The CTD is powered up and allowed to stabilize at 12 m prior to profiling and once stable (typically 4 minutes) the CTD is brought back to the surface from which point the profile begins with typical descent rates of 0.7-1.0 m/s, depending on weather conditions. Water samples are collected on the upcast and prior to triggering bottles the CTD is kept at the desired depth for a minimum of 60 seconds to ensure that entrainment from the following wake has subsided. Once the water sample is taken the CTD immediately continues with the upcast at an ascent rate of 0.7-1.0 m/s. </p>
<p> </p></div>
<div><p>Profiles of basic CTD measurements of (Pressure, Depth, Temperature, Conductivity, and Salinity) are reported along with dissolved oxygen, beam attenuation, and relative fluorescence, at one-decibar averages. The profiles were collected during biweekly cruises to the site known as Hydrostation S (32°10′N 64°30′W). </p></div>
CTD data from Hydrostation S
<div><p><strong>Data processing:</strong><br />
CTD data processing typically follows the procedures outlined in Knap et al., 1996 and can be divided into two major stages: (1) CTD signal conversion and dynamic sensor correction, and; (2) static drift corrections and empirical field calibrations. Stage 1 is performed using SeaBird's SEASOFT software and some Matlab scripts, while Stage 2 is performed completely in the Matlab environment. The basic steps of Stage 1 are: preliminary CTD sensor quality check; determination of the dynamic coefficients associated with time alignment and thermal mass problems; application of pressure filter and velocity filter (0.3 m/s); application of digital filters for erroneous signal removal; and finally average to 2 Hz ready for Stage 2 processing. The processing steps in Stage 2 include: static drift corrections as determined from the sensor calibration history; empirical field calibration of the conductivity and oxygen sensors; final QC analysis; and bin average downcast data to 2 dbar. Following experience of profiling with the SBE–35RT temperature probes, appropriate routines are being implemented to assess performance of the SBE–03f units against the SBE–35 and implement correction procedures. It should be noted that only downcast data are processed and reported, except for the marker data during bottle fires on the upcast.</p>
<p><strong>Instrument calibration:</strong><br />
CTD sensor calibration<em>:</em> Temperature, conductivity and dissolved oxygen sensors are routinely returned to SeaBird every 6-9 months for routine calibration, while the pressure unit is calibrated following full service of the underwater SBE 9 unit every 18-24 months. Auxiliary instruments ( fluorometer, tranmissometer, PAR) are sent for calibration every 12 months.</p>
<p><strong>Quality control data access note:</strong><br />
Data fields that have a WHPO quality flag =3 hav been deemed questionable by the PIs, so any individual accessing the data should be aware that they are accessing data of questionable quality. </p>
<p>--------------------------------------------------------------------</p>
<p>BCO-DMO Processing Notes:<br />
- <span style="font-family:arial; font-size:10pt">added conventional header with dataset name, PI name, version date<br />
- modified parameter names to conform with BCO-DMO naming conventions<br />
- replaced NaN and -999 with the fill value 'nd'</span></p>
<div> </div>
<div> </div>
<p> </p></div>
860014
CTD data from Hydrostation S
2021-09-03T15:59:28-04:00
2021-09-03T15:59:28-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:860014
CTD data collected at the Hydrostation S site in the Sargasso Sea from 1988 onward
false
Bates, N., Johnson, R. J. (2021) CTD data collected at the Hydrostation S site in the Sargasso Sea from 1988 onward. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2021-09-07 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/860014 [access date]
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2021-09-07
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