Metadata Report for BODC Series Reference Number 742864
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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Parameters |
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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
COR2/03 CTD Instrument Description
Instrument Type | Manufacturer and Model | Serial Number | Manufacturer's Description Available? |
---|---|---|---|
CTD | Falmouth Scientific Inc. CTD | 1351 and 1366 | No |
Light Sensor | LICOR | 5671 | No |
Fluorometer | Seapoint Chlorophyll Fluorometer | 2289 | Yes |
Turbidity Sensor | Seapoint Turbidity Meter | Unknown | Yes |
Digital Reversing Thermometer | Unknown | Unknown | No |
Falmouth Scientific Integrated CTD (ICTD) Profiler
The FSI ICTD is designed to collect high precision conductivity, temperature and pressure data with self calibrating electronics. This instrument can support five primary sensors (including up to three temperature sensors) and can be coupled with a water bottle sampler. The ICTD is equipped with a titanium housing rated to 7000 m and has a sampling rate of 32 Hz.
Three temperature sensors are available: primary platinum, redundant platinum and exposed thermistor. Any combination of these can be used in the primary channels. The instrument also has multiple RS-232 serial inputs for a variety of sensors including: ADCP, Benthos PSA-916 Altimeter and WetLabs SAFire. There are an additional eight DC input channels that can support virtually any sensor that has a DC output.
Specifications:
Parameter | Conductivity | Temperature | Pressure |
Sensor | Inductive cell | Platinum thermometer | Precision-machined Silicon |
Range | 0 to 70 mS cm-1 | -2 to 35°C | Customer specified |
Accuracy | ±0.002 mS cm-1 | 0.002°C | ±0.01 % full scale |
Resolution | 0.0001 mS cm-1 | 0.00005°C | 0.0004 % full scale |
Response | 5.0 cm at 1 ms-1 | 150 ms Platinum 20 ms Thermistor* | 25 ms |
*Optional
Further details can be found in the manufacturer's specification sheet.
Seapoint Chlorophyll Fluorometer
The Seapoint Chlorophyll Fluorometer (SCF) is a low power instrument for in situ measurements of chlorophyll a. The SCF uses modulated blue LED lamps and a blue excitation filter to excite chlorophyll a. The fluorescent light emitted by the chlorophyll a passes through a red emission filter and is detected by a silicon photodiode. The low level signal is then processed using synchronous demodulation circuitry which generates an output voltage proportional to chlorophyll a concentration. The SCF may be operated with or without a pump.
Sensor specifications, current at August 2006, are given in the table below. More information can be found at the manufacturer's web site.
Sensor Specifications
Power requirements | 8 - 20 VDC, 15 mA avg., 27 mA pk. |
---|---|
Output | 0 - 5.0 VDC |
Output Time Constant | 0.1 sec. |
Power-up transient period | < 1 sec. |
Excitation Wavelength | 470 nm CWL, 30 nm FWHM |
Emission Wavelength | 685 nm CWL, 30 nm FWHM |
Sensing Volume | 340 mm3 |
Minimum Detectable Level | 0.02 µg l-1 |
Gain | Sensitivity, V µg-1 l-1 | Range, µg l-1 | |
---|---|---|---|
Sensitivity/Range | 30x 10x 3x 1x | 1.0 0.33 0.1 0.033 | 5 15 50 150 |
BODC Processing
The data arrived at BODC in one ASCII format file per cast. These files were reformatted to the BODC internal netCDF subset, QXF, using the transfer function 268. The following table shows how the variables within the ASCII files were mapped to the appropriate BODC parameter codes:
Originator's Parameter Name | Units | Description | BODC Parameter Code | Units | Comments |
---|---|---|---|---|---|
Pressure | decibars | Pressure corrected against deck readings | PRESPR01 | decibars | |
Temperature | °C | Calibrated temperature | TEMPST01 | °C | |
Salinity | N/A | Calibrated salinity | PSALCC01 | N/A | Salinity calibrated by comparison with bottle samples |
Potential temperature | °C | POTMCV01 | °C | ||
Sound velocity | m s-1 | Velocity of sound in the water column | SVELCT01 | m s-1 | |
Sigma-Theta | kg m-3 | Density calculated using potential temperature | SIGTEQ01 | kg m-3 | Sigma-Theta calculated using UNESCO SVAN algorithm |
Sigma-T | kg m-3 | Density calculated using in-situ temperature | SIGTEQST | kg m-3 | Sigma-T calculated using UNESCO SVAN algorithm |
Svan | m3 kg-1 | Specific volume anomaly | Not for transfer - result of calculation step | ||
Dynht | N/A | Dynamic height of the sea surface | Not for transfer - result of calculation step | ||
BVF - CPH | N/A | Brunt Vaisala frequency | Not for transfer - result of calculation step | ||
Depth | metres | Not for transfer - use the pressure measurements | |||
Suspended Load | mg l-1 | Concentration of suspended particulate matter | TSEDBSCL | mg l-1 | Turbidity sensor calibrated against water samples collected during CTD upcast. Where channel was all null values for a cast, it was removed from the final file. |
Radiance | lgnA | Not for transfer - use derivative of PAR data | |||
PAR | microE m-2 s-1 | Photosynthetically active radiation | IRRDSV01 | microE m-2 s-1 | Where channel was all null values for a cast, it was removed from the final file. |
Fluoresence | V | Instrument output from chlorophyll fluorometer | FVLTWS01 | V | |
Chlorophyll | mg m-3 | Calibrated chlorophyll concentration | CPHLPR01 | mg m-3 | Fluorometer calibrated against water samples collected during CTD upcast. Some casts had null values for each cycles, deemed as bad data by the originator. Where this occurred the channel was removed. |
The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.
COR2/03 CTD Originator's Data Processing
Sampling strategy
A total of 43 full depth CTD profiles were obtained during the cruise to the North Sea. For all stations water samples were collected for salinity analysis (using a Guildline salinometer) to derive a calibration for the CTD conductivity sensor. A pair of digital reversing thermometers were used to verify the calibration of the CTD temperature sensors.
A Seapoint fluorometer sensor, Seapoint turbidity sensor and a LICOR photosynthetically active radiation sensor (with a six-decade log amplifier) were fitted to the CTD rosette for all stations. Chlorophyll samples were collected from the water column to calibrate the fluorometer.
Field Calibrations
Pressure
During the cruise, the 'on-deck' CTD pressure measurements immediately prior to the CTD unit being lowered into the water column were recorded. These 'on-deck' measurements were used to correct the recorded CTD pressure as follows:
P(corrected) = P(uncorrected) + dP;
s/n 1351: dP = 0.6 decibars
s/n 1366: dP = 1.2 decibars
Temperature
The platinum resistance temperature sensor fitted to the CTD unit was calibrated against platinum resistance thermometers on 02/01/2002 (using triple point cell coefficients determined on 21st January 2001) and this was used to correct the temperature recorded by the CTD:
T(corrected) = T(uncorrected) + dT;
where: dT = a*T(uncorrected)2 + b*T(uncorrected) + c
and: a = 4.47 * 10-5; b = -3.355 * 10-4; c = 5.698 * 10-3 for s/n 1351
and: a = -5.3 * 10-5; b = -6.817 * 10-4; c = -2.162 * 10-3 for s/n 1366
This is equivalent to a correction of between 5 and 10 m°C in the range 4 - 14 °C for s/n 1351 and between -3 and 0 m°C for s/n 1366.
One pair of digital reversing thermometers were used during the cruise fitted to a Niskin water sampling bottle fired close to the seabed. No thermometer for s/n 1366. The differences are greater than expected but this is probably a consequence of poor thermometer.
Conductivity
A least squares fit was used to determine the appropriate calibration coefficients:
CR(corrected) = CR(ctd)[A*T(corrected) + b*(P(corrected) + c]
where: CR(ctd) = Conductivity ratio from the CTD
CR(corrected) = Corrected conductivity ratio
s/n 1351: a = -2.2697513 * 10-5; b = -8.5571339 * 10-7; c = 1.0001718
s/n 1366: a = 1.204822 * 10-5; b = 9.503581 * 10-7; c = 0.9994995
Using these coefficients the root mean square difference between the water sample (salinometer) salinities and the corrected CTD salinities is 0.002 (20 samples) for s/n 1351 and 0.003 (13 samples) for s/n 1366. It is assumed that the CTD conductivity is accurate to 0.01 and that the salinometer is accurate to 0.003. Therefore salinity differences to the magnitude of 0.013 are acceptable. Following the calibrations, all differences are within magnitude 0.007.
Fluorometer - Chlorophyll
A Seapoint Chlorophyll Fluorometer was fitted to the CTD rosette sampler. The instrument was calibrated by comparing the recorded voltages with the measured chlorophyll in water samples collected by Niskin bottles on the CTD upcast. The following equation was used:
Chlorophyll = a * Fluorometer(volts) + b
Stations 1-12, 14, 23, 24, 155 and 161: a = 27.47; b = -0.22; R2 = 0.80; Number of samples = 12
Stations 13, 15, 16 and 25-120: a = 86.96; b = -0.45; R2 = 0.68; Number of samples = 48
Suspended Load
A Seapoint Turbidity Meter was fitted to the CTD rosette sampler and used to estimate the suspended load concentrations. The sensor was calibrated by comparing the recorded voltages with measured suspended load concentrations collected on the CTD upcast:
Suspended Load = a * Turbidity(volts) + b
Stations 1-32, 140-161: a = 5.208; b = -0.430; R2 = 0.97; Number of samples = 13
Stations 38, 45, 52, 121 and 124: a = 4.931; b = -0.053; R2 = 0.99; Number of samples = 8
Stations 78-115: a = 4.587; b = 0.331; R2 = 0.99; Number of samples = 6
Photosynthetically Active Radiation
The LICOR light sensor used to measure photosynthetically active radiation was calibrated during June 2001 using a standard lamp. This gave an in-air current equivalent to 0.3461 micromoles m-2 s-1 nanoAmp-1 in water.
Project Information
No Project Information held for the Series
Data Activity or Cruise Information
Cruise
Cruise Name | COR2/03 |
Departure Date | 2003-01-27 |
Arrival Date | 2003-02-08 |
Principal Scientist(s) | David Brian Sivyer (Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory) |
Ship | RV Corystes |
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 |