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Metadata Report for BODC Series Reference Number 326153


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Guildline Model 8705 Digital CTD  salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Ministry of Agriculture, Fisheries and Food Lowestoft Fisheries Laboratory (now Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) -
 

Data Identifiers

Originator's Identifier CI6/89/45
BODC Series Reference 326153
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1989-06-30 15:10
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 65.85330 N ( 65° 51.2' N )
Longitude 28.26500 W ( 28° 15.9' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 4.4 m
Maximum Sensor or Sampling Depth 592.7 m
Minimum Sensor or Sampling Height 10.3 m
Maximum Sensor or Sampling Height 598.6 m
Sea Floor Depth 603.0 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
 

Parameters

BODC CODERankUnitsTitle
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
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

No Problem Report Found in the Database


Data Access Policy

Centre for Environment, Fisheries and Aquaculture Science (Cefas) data access conditions

The Centre for Environment, Fisheries and Aquaculture Science (Cefas) is an Executive Agency of the Department of Environment, Food and Rural Affairs (Defra), formerly the Ministry of Agriculture, Fisheries and Food (MAFF). It was also known previously as the Directorate of Fisheries Research (DFR). This data policy refers to data collected by the organisation under all titles.

  • These data have no specific confidentiality restrictions for academic users. However data are restricted for commercial requests and clearance must be obtained by BODC from Cefas before they are released.
  • 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 acknowledgement.
  • The recommended acknowledgement is: "This study uses data from the Centre for Environment, Fisheries and Aquaculture Science (Cefas), provided by the British Oceanographic Data Centre."

Narrative Documents

Guildline 8705 CTD

The 8705 CTD is a conductivity-temperature-pressure profiler designed for marine applications down to depths of 6000 m. The instrument includes an anodised aluminium tube with a steel cage to protect the temperature and conductivity sensors and a urethane cap to protect the pressure sensor.

Specifications

Parameter Range Accuracy Resolution Stability Response time
Pressure 0 to 6000 dbar ± 0.15% of full range ± 0.01% of full range - < 50 ms
Temperature -2 to 30 °C ± 0.005 °C ± 0.0005 °C

± 0.002 °C over 30 days

± 0.0025°C over 6 months

< 50 ms
Conductivity * 100 ppm to 40 ppt ± 0.005 ppt ± 0.001 ppt ± 0.002 ppt over 6 months < 50 ms

* Conductivity specifications are given in terms of equivalent salinity

Further details can be found in the manufacturer's specification sheet.

RV Cirolana Cruise 6/1989 CTD Data Documentation

Instrumentation

The CTD used was S/N 41136.

Calibrations and Data Quality

Pressure and temperature sensors were corrected using coefficients determined after laboratory calibrations. Water samples collected during the ascent of the CTD for salinity analysis with a Guildline salinometer were used to calibrate the conductivity sensor.

Pressure

The pressure sensor was calibrated with a dead weight tester before and after the cruise, during June and August 1989. However, the temperature of the sensor was near 7.5degC for all of the August calibration and during the June calibration the temperature/pressure values did not reflect the conditions encountered during the cruise. The calibration was repeated using appropriate temperature/pressure coordinates during November: see Fig. 1.

P(COR) = P(CTD) + PA*T(COR) + PB*P(CTD) + PC

where:

T(COR) = corrected CTD temperature.
PA = -8.4343 E-2
PB = 3.1313 E-3
PC = 2.09

This calibration was in good agreement with that suggested by comparing pressures derived from unprotected thermometers and those recorded by the CTD.

Temperature

Good agreement was obtained between pre- and post-cruise calibrations using platinum resistance thermometers (although only PRT 2503 gave reliable measurements).

DSRTs were used on each CTD cast and suggested a correction which differed from the laboratory calibration by 16 mK, within the tolerance of the thermometers.

Temperatures were corrected using the pre-cruise calibration of June 1989:

T(COR) = T(CTD) + TA* T(CTD)* T(CTD) + TB*T(CTD) + TC
TA = -3.2311 E-5
TB = 7.1947 E-5
TC = 2.75 E-4

Conductivity ratio

The conductivity ratio of the water sample salinity, CR(WS), at its in situ pressure and temperature was compared with that measured by the CTD, CR(CTD). The ratio CR(WS):CR(CTD) was then fitted by least squares to satisfy the equation

[CR(WS)/CR(CTD)]= CA * T(CTD) + CB * P(CTD) + CC
where T(CTD) and P(CTD) are the corrected CTD temperature and pressure.

The variation in the ratio CR(WS): CR(CTD) is seen in Fig. 2.

Solving the above equation and calculating an estimate of CTD salinity yielded an rms difference between water sample and CTD salinity of 0.003 for 95 observations. This is within the expected tolerance of the CTD and no attempt was made to determine cell factors, CF, for each station.

CR(COR) = CR(CTD) * [CF * (CA * T(COR) + CB * P (POR) + CC]

where

CF = 1.0
CA = -0.29928 E-5
CB = 6.10159 E-9
CC = 1.00145

Fig. 3 shows how effective these coefficients are in correcting the CTD estimates of salinity.

Ken Medler
14 June 1991

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

  • Irregularities such as unfeasible values
  • Inconsistencies between related information, for example:
    • Times for instrument deployment and for start/end of data series
    • Length of record and the number of data cycles/cycle interval
    • Parameters expected and the parameters actually present in the data cycles
  • Originator's comments on meter/mooring performance and data quality

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

  • Spurious data at the start or end of the record.
  • Obvious spikes occurring in periods free from meteorological disturbance.
  • A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

  • Maximum and minimum values of parameters (spikes excluded).
  • The occurrence of meteorological events.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name CIR6/89
Departure Date 1989-06-21
Arrival Date 1989-07-20
Principal Scientist(s)Robert R Dickson (Ministry of Agriculture, Fisheries and Food Lowestoft Fisheries Laboratory)
Ship RV Cirolana

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