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Metadata Report for BODC Series Reference Number 1072837

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Tony Bale
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Atlantic Meridional Transect (AMT)

Data Identifiers

Originator's Identifier CTDP031
BODC Series Reference 1072837

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1997-05-10 12:42
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 1.89850 N ( 1° 53.9' N )
Longitude 25.62833 W ( 25° 37.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 2.49 m
Maximum Sensor or Sampling Depth 199.3 m
Minimum Sensor or Sampling Height 3625.1 m
Maximum Sensor or Sampling Height 3821.91 m
Sea Floor Depth 3824.4 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface


BODC CODERankUnitsTitle
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALCC011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and calibration against independent measurements
SIGTPR011Kilograms per cubic metreSigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPCC011Degrees CelsiusTemperature of the water body by CTD and verification against independent measurements

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

James Clark Ross Cruise AMT4 CTD Instrumentation


Neil Brown Mark IIIB (Instrument Systems, Inc.) CTD
Rosette fitted with 12 10-litre General Oceanics water bottles.

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.


These specification apply to the MK3C version.

Pressure Temperature Conductivity

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm-1

0.0015% FS

0.03% FS < 1 msec


0.003°C < 30 msec

0.0001 S cm-1

0.0003 S cm-1 < 30 msec

Further details can be found in the specification sheet.

James Clark Ross Cruise AMT4 CTD Processing

Originator's Processing

The CTD profiles were processed onboard using RVS software.

BODC data processing

  • Reformatting

    The data files were sent to BODC in RVS internal format. All available channels were listed into ASCII format using RVS software. Non-null channels were then converted to PXF, a BODC internal format. The data were processed from 1Hz averaged down- and upcast data. Sigma-theta was calculated and output from the raw data during the conversion to PXF format.


    Originator's Parameter Originator's Units Description BODC code BODC Units Comments
    press decibars Pressure PRESPR01 decibars -
    temp °C Temperature TEMPCU01 °C -
    salin - Salinity PSALCU01 - -
    - - Temperature - calibrated TEMPCC01 °C Calibrated against reversing thermometer data
    - - Salinity - calibrated PSALCC01 - Calibrated against bottle salinity data
    - - Potential temperature POTMCV01 °C Computed using UNESCO POTEMP function
    - - Sigma-theta SIGTPR01 kg m-3 Computed using UNESCO SVAN function
  • Screening

    The PXF data were compared with the original data files to ensure that no errors had been introduced during the conversion process. The data channels were then screened on a graphics workstation using in-house visualisation software. This allows multiple channels to be viewed simultaneously. The start and end-points of the downcast were marked. The pressure ranges over which bottles were fired were also marked. The bottle firing events were identified by disturbances in CTD parameters on the upcast profiles. All spurious and null data were flagged with appropriate BODC quality control flags.

    The following notes were made during screening of AMT4 data.

    CTDP029 had a limited downcast, so the upcast data were used for further processing.
    CTDP057 showed a disturbance in the salinity signal between 127 and 180 db - this section was flagged as suspect.

    The quality of the data appeared to be good.

  • Loading into the BODC database

    After the data had been screened and quality controlled, the data were loaded into the BODC database under the Oracle RDBMS.

    The data from 66 casts were loaded into the data tables.


Calibration of the temperature and salinity calibrations had been made during the cruise by scientific personnel, but no corrections had been applied to the data. The results of the calibration exercise are published in the AMT4 cruise report, p.49, section 4.5.1, 'Salinity and Temperature Calibrations':

  • Pressure

    The pressure sensor had a mean reading of 1.5 decibar while the CTD was logging in air - this was identified during BODC processing. A pressure correction was, therefore, applied to the data when they were listed from the BODC database.

    PRESPR01(corr) = PRESPR01(raw) - 1.5 decibar (BODC calibration 1588)

  • Temperature

    TEMPCC01 = 0.9995 * TEMPCU01 + 0.02222 (r2 = 1.00)
    This correction was applied to the data at BODC (BODC calibration 1598)

  • Salinity

    PSALCC01 = 1.004 * PSALCU01 - 0.1364 (r2 = 0.9998)
    This correction was applied to the data at BODC (BODC calibration 1592)

Project Information

The Atlantic Meridional Transect (AMT) - Phase 1 (1995-2000)

Who was involved in the project?

The Atlantic Meridional Transect (AMT) programme was designed by and implemented as a collaboration between Plymouth Marine Laboratory (PML) and Southampton Oceanography Centre (SOC). The programme was hosted by Plymouth Marine Laboratory and involved additional researchers from UK and international universities throughout its duration.

What was the project about?

When AMT began in 1995 the programme provided a platform for international scientific collaboration, including the calibration and validation of SeaWiFs measurements and products. The programme provided an exceptional opportunity for nationally and internationally driven collaborative research and provided a platform for excellent multi-disciplinary oceanographic research. As an in situ observation system, the data collected by the AMT consortium informed on changes in biodiversity and function of the Atlantic ecosystem during this period of rapid change to our climate and biosphere.

The scientific aims were to assess:

  • mesoscale to basin scale phytoplankton processes
  • the functional interpretation of bio-optical signatures
  • the seasonal, regional and latitudinal variations in mesozooplankton dynamics

When was the project active?

The first phase of the AMT programme ran from 1995 to 2000 and consisted of a total of 12 cruises. A second phase of funding allowed the project to continue for the period 2002 to 2006 with a further 6 cruises.

Brief summary of the project fieldwork/data

The AMT programme undertook biological, chemical and physical oceanographic research during the annual return passage of the RRS James Clark Ross between the UK and the Falkland Islands or the RRS Discovery between the UK and Cape Town, a distance of up to 13,500 km. This transect crossed a range of ecosystems from sub-polar to tropical and from euphotic shelf seas and upwelling systems to oligotrophic mid-ocean gyres. The transect route was covered north-south in September/October and south-north in April/May of each year.

The measurements of hydrographic and bio-optical properties, plankton community structure and primary production completed on the first 12 transects (1995-2000) represent the most coherent set of repeated biogeochemical observations over ocean basin scales. This unique dataset has led to several important discoveries concerning the identification of oceanic provinces, validation of ocean colour algorithms, distributions of picoplankton, identifying new regional sinks of pCO2 and variability in rates of primary production and respiration.

Who funded the project?

The programme was funded by the Natural Environment Research Council (NERC) and further support was received from the National Aeronautics and Space Administration (NASA) with equipment and funding from the Sea-viewing Wild Field-of-view Sensor (SeaWiFS) project.

Data Activity or Cruise Information


Cruise Name JR19970421 (AMT4, JR21)
Departure Date 1997-04-21
Arrival Date 1997-05-27
Principal Scientist(s)Tony Bale (Plymouth Marine Laboratory)
Ship RRS James Clark Ross

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
Q value below limit of quantification