Data processing:
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.
Instrument calibration:
CTD sensor calibration: 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.
Quality control data access note:
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.
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BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- replaced NaN and -999 with the fill value 'nd'