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Metadata Report for BODC Series Reference Number 58428


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 CIRO8/84/070
BODC Series Reference 58428
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1984-10-05 23:36
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 41.41660 N ( 41° 25.0' N )
Longitude 13.93330 W ( 13° 56.0' W )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor or Sampling Depth 5.75 m
Maximum Sensor or Sampling Depth 2540.06 m
Minimum Sensor or Sampling Height 2804.94 m
Maximum Sensor or Sampling Height 5339.25 m
Sea Floor Depth 5345.0 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

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

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 8/1984 CTD Data Documentation

Introduction

This data document covers the CTD data collected on RV Cirolana 8/1984 (September - October 1984) by the Ministry of Agriculture, Fisheries and Food, Fisheries Laboratory, Lowestoft, Suffolk, UK, under the direction of K.J. Medler.

Instrumentation

The instrument used was a Guildline Model 8705 Digital CTD which measured pressure, temperature and conductivity. The CTD was used alongside a General Oceanics Rosette Multisampler fitted with water bottles and was fitted with an acoustic altimeter with digital display to measure the height of the CTD above the sea bed.

Sampling Protocol

Lowering and retrieval speeds of 1 m/s were employed. Bottle sample and reversing thermometer measurements were made on ascent and sea water samples were analysed using a Guildline Autolab Salinometer.

Calibrations

Pressure

Calibrated in the laboratory before and after the cruise using a deadweight tester at carefully selected temperatures. A correction term of the form:

deltaP = A * T (CTD) + B + P (CTD) + C

is obtained and applied as:

P (corrected) = P (CTD) + deltaP

The calibration is checked in the field when possible by using altimeter measurements of height above the sea bed.

Temperature

The temperature sensor was calibrated in the laboratory immediately before and after the cruise using platinum resistance thermometers. A correction equation is obtained by fitting the difference between the CTD and platinum resistance thermometers to a quatratic equation using least squares.

T (corrected) = T (CTD) + deltaT

where

deltaT = A * T (CTD)2 + B * T (CTD) + C

The calibration is checked in the field by comparing the CTD data with reversing thermometer measurements.

Salinity

A comparison between in situ conductivity ratio of water samples (calculated using the algorithms given by Fofonoff and Millard (1983)) and measured CTD conductivity ratio enables coefficients a, b and c to be found in the equation:

CR (sample)/CR (CTD) = a * T + b * P + C

The CTD conductivity ratio is then corrected by:

CR (corrected) = CR (CTD) * (a * T + b * P + C)

After correcting the CTD data, as described above, a comparison was made with the potential temperature (POTT) - Salinity (S) relationship suggested by Saunders (1983):

S = 34.698 + 0.098 * POTT for North Atlantic Deep Water where POTT is less than 2.7 °C.

Comparison with Saunders POTT-S relationship was only possible at the four full depth stations (28, 44, 46 and 48). The agreement in salinity is good for these with rms differences less than or equal to 0.006.

The conductivity ratio calibration was carried out using 109 water samples, some being duplicates.

Data Processing

Data came in at 25 frames/sec and were logged on an Apricot disk, and could be plotted. At the end of each station the data were transferred to an HP1000 computer. The raw data were then averaged over 25 observations every 100 observations. This resulted in data values averaged over approximately 1db with a value every 4db.

Calibration coefficients and correction factors were applied. Derived quantities were computed from algorithms published by Fofonoff and Millard (1983).

References

Fofonoff, N.P. and Millard, R.C. Jr., 1983.
Algorithms for the computation of fundamental properties of sea water. UNESCO Technical Paper on Marine Science 44.

Saunders, P.M. 1983.
CTD data from the north east Atlantic Ocean 31° N - 46° N, July 1982. RRS Discovery Cruise 130. Institute of Oceanographic Sciences. Report No. 165.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name CIR8/84
Departure Date 1984-09-25
Arrival Date 1984-10-11
Principal Scientist(s)Paul A Gurbutt (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
B nominal value
Q value below limit of quantification