Metadata Report for BODC Series Reference Number 743486
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
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
COR8/03 CTD Instrument Description
Instrument Type | Manufacturer and Model | Serial Number | Manufacturer's Description Available? |
---|---|---|---|
CTD | Falmouth Scientific Inc. CTD | 1351 (3 stations) and 1366 (56 stations) | No |
Light Sensor | LICOR | 5671 | No |
Fluorometer | Seapoint Chlorophyll Fluorometer | 2289 | Yes |
Turbidity Sensor | Seapoint Turbidity Meter | 1610 | 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 |
LI-COR LI-192 Underwater Quantum Sensor
The LI-192 Underwater Quantum Sensor is used to measure photosynthetic photon flux density and is cosine corrected. The sensor is often referred to as LI-192SA or LI-192SB (the LI-192SB model was superseded by LI-192SA). One of the main differences is that the LI-192SA model includes a built-in voltage output for interfacing with NexSens iSIC and SDL data loggers.
Sensor specifications, current at January 2012, are given in the table below. More information can be found in the manufacturer's LI-192SA andLI-192SB specification sheets.
Sensor Specifications
(Specifications apply to both models unless otherwise stated)
Absolute Calibration | ± 5 % in air traceable to NBS. |
---|---|
Sensitivity | Typically 3 µA per 1000 µmol s-1 m-2 for LI-192SB and 4 µA per 1000 µmol s-1 m-2 for LI-192SA in water. |
Linearity | Maximum deviation of 1 % up to 10,000 µmol s-1 m-2. |
Stability | < ± 2 % change over a 1 year period. |
Response Time | 10 µs. |
Temperature Dependence | ± 0.15 % per °C maximum. |
Cosine Correction | Optimized for both underwater and atmospheric use. |
Azimuth | < ± 1 % error over 360 ° at 45 ° elevation. |
Detector | High stability silicon photovoltaic detector (blue enhanced). |
Sensor Housing | Corrosion resistant metal with acrylic diffuser for both saltwater and freshwater applications. Waterproof to withstand 800 psi (5500 kPa) (560 meters). |
Seapoint Turbidity Meter
The Seapoint Turbidity Meter detects light scattered by particles suspended in water, generating an output voltage proportional to turbidity or suspended solids. Range is selected by two digital lines which can be hard wired or microprocessor controlled, thereby choosing the appropriate range and resolution for measurement of extremely clean to very turbid waters. The offset voltage is within 1 mV of zero and requires no adjustment across gains. The optical design confines the sensing volume to within 5 cm of the sensor allowing near-bottom measurements and minimizing errant reflections in restricted spaces.
Sensor specifications, current at August 2006, are given in the table below.
Sensor Specifications
Power requirements | 7 - 20 VDC, 3.5 mA avg., 6 mA pk. |
---|---|
Output | 0 - 5.0 VDC |
Output Time Constant | 0.1 sec. |
RMS Noise> | < 1 mV |
Power-up transient period | < 1 sec. |
Light Source Wavelength | 880 nm |
Sensing Distance (from windows) | < 5 cm (approx.) |
Linearity | < 2% deviation 0 - 750 FTU |
Gain | Sensitivity (mV FTU-1) | Range (FTU) | |
---|---|---|---|
Sensitivity/Range | 100x 20x 5x 1x | 200 40 10 2 | 25 125 500 ** |
** output is non-linear above 750 FTU.
Further details can be found in the manufacturer's specification sheet.
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.
COR8/03 CTD Originator's Data Processing
Sampling strategy
A total of 59 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. Two pairs of digital reversing thermometers were used to verify the calibration of the CTD temperature sensor.
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. Chlorophyll samples were collected from the water column to calibrate the fluorometer. No samples were taken at stations 28, 29 and 30.
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 during March 2003 for S/N 1351 and June 2003 for S/N 1366 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
S/N 1351: a = 4.47 * 10-5; b = -3.355 * 10-4; c = 5.6976 * 10-3
S/N 1366: a = -5.4385 * 10-5; b = 6.9345 * 10-4; c = -2.2 * 10-3
This is equivalent to a correction of between 0 and -3 m°C in the range 4 - 14 °C for S/N 1366.
Conductivity
A least squares fit was used to calibrate the CTD conductivity readings to the salinometer data acquired from the water bottle samples:
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 1366: a = -0.12107993 * 10-4; b = -0.979370043 * 10-6; c = 0.999687975
Using these coefficients, the root mean squared difference between the water sample (salinometer) and corrected CTD salinity for S/N 1366 is 0.003 (81 samples). 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 points are within this range.
Fluorometer - Chlorophyll
A Seapoint Chlorophyll Fluorometer was fitted to the CTD rosette sampler. The instrument was and 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 48-290: a = 1.68663; b = -0.38472; R2 = 0.7961; Number of samples = 109
Suspended Load
A Seapoint Turbidity Meter (s/n 1610) 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
All stations: a = 13.4953; b = -0.5034; R2 = 0.2911; Number of samples = 39
Photosynthetically Active Radiation
The LICOR sensor was not working on CTD S/N 1351.
The LICOR light sensor for CTD S/N 1366 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 | COR8/03 |
Departure Date | 2003-06-26 |
Arrival Date | 2003-07-09 |
Principal Scientist(s) | Liam Fernand (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 |