Metadata Report for BODC Series Reference Number 58428
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
SeaDataNet Quality Flags
Metadata Summary
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Problem Reports
No Problem Report Found in the Database
Data Access Policy
Open 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.
If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:
"Contains public sector information licensed under the Open Government Licence v1.0."
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 |