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Metadata Report for BODC Series Reference Number 475866


Metadata Summary

Data Description

Data Category Towed STD/CTD
Instrument Type CTD in towed or autonomous underwater vehicle
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Institute of Oceanographic Sciences Wormley Laboratory (now National Oceanography Centre, Southampton)
Processing Status QC in progress
Online delivery of data Download not available
Project(s) -
 

Data Identifiers

Originator's Identifier GR164018
BODC Series Reference 475866
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1987-01-14 12:43
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 39.67975 S ( 39° 40.8' S )
Longitude 52.20755 E ( 52° 12.5' E )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 6.0 m
Maximum Sensor or Sampling Depth 395.4 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 Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

No Parameters for BODC Reference Number = 475866

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

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."


Narrative Documents

RRS Discovery 164 CTD Data Documentation

Introduction

This document covers the CTD data collected during RRS Discovery cruise 164 (19th December 1986 to 21st January 1987) under the direction of Dr R.T. Pollard from the Institute of Oceanographic Sciences Deacon Laboratory. The data were collected in the S Atlantic and SW Indian Ocean.

Instrumention

The instrument used was a Neil Brown Instrument Systems (NBIS) CTD, which measured pressure, temperature and conductivity. The CTD was used alongside a General Oceanics Rosette Multisampler with 12 Niskin bottles and a 10 kHz pinger. The sensors were flushed with distilled water on recovery. Bottle samples and reversing thermometer measurements were made on descent and the sea water samples were analysed using a Guildline Autolab Salinometer.

Reversing thermometers were calibrated before and after the cruise.

Sampling Protocol

Lowering and retrieval rates of 0.5 to 1.0 m/s were employed. All casts were full depth, most proceeding to within 10-30 m of the bottom.

Data were initially logged at 16 hz from the NBIS CTD onto an NBIS deck unit, which had been enhanced by IOS with an ASCII interface, allowing raw data to be written to a 1600 bpi 0.5 inch magnetic tape. Data are then passed to a microcomputer which edited and averaged the raw data to 1 hz, using algorithms developed by Pollard et al. (1986). All SMP messages from all instruments were archived using a Plessey 68000 and a UNIX based Plessey 68000 was available for further processing. CTD data were then analysed using editing, utility and display programs (Pollard, 1983). Further details of the processing can be found in Pollard et al. (1987).

Calibration

Pressure

Raw pressure R(raw) was calibrated to dbar P(cal) by the formula

P(cal) = 0.1 * P(raw) - 12.0

The pressure calibration was checked by comparing the CTD depth at the bottom of each cast with the value derived from the IOS Precision Echo Sounder. In total, 35 values fell within a Gaussian distribution which tailed off at 15m, and these values yielded:

D(pes) - D(ctd) = 0.4 +/- 6.3

From this it was deduced that pressures were therefore probably correct within a few decibars.

Temperature

CTD temperatures were calibrated at sea using the most recent laboratory calibration

T(C) = T(raw) * 0.0005 * 0.9990317 + 0.0258

which reinforced the long-term stability of the platinum resistor calibration. Reversing thermometers were deployed at two depths on all casts, to check for gross errors and, on the evidence gained, no change was made to the CTD temperature calibration.

Salinity

An overall correction of 0.050 given by all 165 values for casts 11404-58, with a standard deviation of 0.005, was applied. Casts 11401-03 were individually corrected by 0.027, 0.036 and 0.045 respectively. After cast 11458, a new conductivity sensor had to be installed, and calibration points available for casts 11459-61 were found to be unreliable. Therefore, a correction of -0.019 was applied to all three casts.

Oxygen

Offsets between up-casts and down-casts were minimised by replacing lagged temperature by unlagged CTD temperature. It was found that the calibration drifted enough that casts had to be fitted individually. Most CTD values were believed to be within 0.1 ml/l of their true value, or certainly 0.2 ml/l.

References

Pollard, R.T. 1983. PSTAR shipboard data processing programs. Institute of Oceanographic Sciences, Marine Physics Group. (Unpublished manuscript)

Pollard, R.T., Holford, D., Ellis, S., Read, J.F. and Smithers, J. 1986.
CTD data from the Northeast Atlantic Ocean 37°-47° N, 10°-16° W collected on RRS Discovery Cruise 145 in late winter 1984. Institute of Oceanographic sciences, Report No. 223.

Pollard, R.T., Read, J.F., Smithers, J. 1987.
CTD sections across the Southwest Indian Ocean and Antarctic Circumpolar Current in Southern Summer 1986/7. Institute of Oceanographic sciences, Report No. 243.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name D164
Departure Date 1986-12-19
Arrival Date 1987-01-21
Principal Scientist(s)Raymond T Pollard (Institute of Oceanographic Sciences Wormley Laboratory)
Ship RRS Discovery

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