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Metadata Report for BODC Series Reference Number 277987


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Barry Heywood
Originating Organization British Antarctic Survey
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) -
 

Data Identifiers

Originator's Identifier JB08/0326
BODC Series Reference 277987
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1988-02-17 21:55
End Time (yyyy-mm-dd hh:mm) 1988-02-17 22:20
Nominal Cycle Interval 1.0 metres
 

Spatial Co-ordinates

Latitude 55.50300 S ( 55° 30.2' S )
Longitude 58.12300 W ( 58° 7.4' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 3.0 m
Maximum Sensor or Sampling Depth 486.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
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 -
 

Parameters

BODC CODERankUnitsTitle
DEPHPR011MetresDepth (spatial coordinate) relative to water surface in the water body by profiling pressure sensor and conversion to seawater depth using UNESCO algorithm
SSALPR011Parts per thousandSalinity of the water body by conductivity cell
TEMPST011Degrees CelsiusTemperature of the water body by CTD or STD

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

The data are derived from instruments that were laboratory calibrated but not recalibrated using in-situ sample data, resulting in data of variable quality.

The data originators believe the temperatures to be reasonable but believe the salinity data to be of a quality too poor to be of value to physical oceanographic studies. Checks by BODC showed deep water salinity data to match other cruises from the region and to be within 0.2 ppt of the climatological mean for the area.

The pressure channels for some profiles from this cruise include negative values that are associated with credible temperature and salinity values, casting doubt on the pressure calibration for the cruise. The affected values have been flagged.


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

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.

Specifications

These specification apply to the MK3C version.

Pressure Temperature Conductivity
Range

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm-1
Accuracy

0.0015% FS

0.03% FS < 1 msec

0.0005°C

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.

RRS John Biscoe Cruise 08 CTD Data Documentation

Introduction

Documentation for the CTD data collected on RRS John Biscoe Cruise 08 (28 December 1987 - 11 March 1988) by the British Antarctic Survey, Cambridge, U.K., under the direction of R.B. Heywood.

Data Collection

The instrument used was a Neil Brown Instruments System Mark IIIB CTD. Observed parameters were pressure, temperature and conductivity. All sensors were calibrated before and after the cruise. Up to 12 water bottles were mounted on a Rosette sampler and 4 pairs of reversing thermometers were attached. Water bottles were triggered on the downcast at 10m and at the bottom of the cast, the remainder being fired on the upcast (mainly for chemical samples). Data were collected on the downcast.

Calibration

Reversing thermometers were calibrated at the Deacon Laboratory of the Institute of Oceanographic Sciences. The pressure sensor was compared with a Bourdon gauge which had been calibrated at the National Physical Laboratory. The accuracy of the temperature data is thought to be ±0.01 °C.

Data Processing

Calibrations were applied and the data despiked by rejecting data values outside of predetermined tolerances. Data values were then averaged to provide data at 1 decibar intervals.

Data Quality

The deep water salinity data from the CTD have been compared with other measurements made in this region and also with the Levitus Atlas. They are in agreement with data collected on various cruises including Discovery II (1929-31) and within about 0.02 ppt of the Levitus Atlas salinities.

Reference

Levitus, S. 1982.
Climatological Atlas of the World Ocean. NOAA Professional Paper No. 13. US Government Printing Office. 173pp


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name JB08
Departure Date 1987-12-28
Arrival Date 1988-03-11
Principal Scientist(s)Julian Priddle (British Antarctic Survey)
Ship RRS John Biscoe

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
B nominal value
Q value below limit of quantification