Metadata Report for BODC Series Reference Number 741271

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Seapoint Turbidity Meter  optical backscatter sensors
Seapoint chlorophyll fluorometer  fluorometers
LI-COR LI-192 PAR sensor  radiometers
Falmouth Scientific Instruments Integrated CTD Profiler  CTD; water temperature sensor; salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory
Processing Status QC in progress
Online delivery of data Download not available
Project(s) -

Data Identifiers

Originator's Identifier CI1X/02/27
BODC Series Reference 741271

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2002-01-18 05:57
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 51.52950 N ( 51° 31.8' N )
Longitude 1.03600 E ( 1° 2.2' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 2.0 m
Maximum Sensor or Sampling Depth 17.0 m
Minimum Sensor or Sampling Height 1.0 m
Maximum Sensor or Sampling Height 16.0 m
Sea Floor Depth 18.0 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 Unspecified -


BODC CODERankUnitsTitle
ACYCAA011DimensionlessSequence number
CPHLPR011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer
FVLTWS011VoltsRaw signal (voltage) of instrument output by linear-response chlorophyll fluorometer
IRRDSV011MicroEinsteins per square metre per secondDownwelling vector irradiance as photons of electromagnetic radiation (PAR wavelengths) in the atmosphere by cosine-collector radiometer
POPTZZ011PercentTransmittance (unspecified wavelength) per unspecified length of the water body by transmissometer
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALCC011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and calibration against independent measurements
SIGTEQ011Kilograms per cubic metreSigma-theta of the water body by computation from salinity and potential temperature using UNESCO algorithm
SIGTEQST1Kilograms per cubic metreSigma-T of the water body by computation from salinity and temperature using UNESCO algorithm
SVELCT011Metres per secondSound velocity in the water body by CTD and computation from temperature and salinity by unspecified algorithm
TEMPST011Degrees CelsiusTemperature of the water body by CTD or STD
TSEDBSCL1Milligrams per litreConcentration of suspended particulate material {SPM} per unit volume of the water body [particulate >unknown phase] by in-situ optical backscatter measurement and calibration against sample data

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.

Narrative Documents

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.


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


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

Instrument Description

Instrument Type Manufacturer and Model Serial Number Manufacturer's Description Available?
CTD Falmouth Scientific Inc. CTD 1366 No
Light Sensor LICOR 5671 No
Fluorometer Seapoint Chlorophyll Fluorometer 2289 Yes
Turbidity Sensor Seapoint Turbidity Meter 1609 Yes
Digital Reversing Thermometer Unknown Unknown No

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

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

** 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
Transmission % Beam transmittance POTPZZ01 % No wavelength or path length specified by the data originator
Suspended Load mg l-1 Concentration of suspended particulate matter TSEDBSCL mg l-1 Turbidity sensor calibrated against water samples collected during CTD upcast
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  
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

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.

Originator's Data Processing

Sampling strategy

A total of 32 full depth CTD profiles were obtained during the cruise to the North Sea, English Channel, Celtic Sea and Irish Sea. For all stations (except 63 and 77) 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 validate 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 for all stations. Chlorophyll samples were collected from the water column to calibrate the fluorometer.

Field Calibrations


The pressure sensor was calibrated using a dead-weight tester on 8th January 2002 at 14°C and an atmospheric pressure of 1005mb, which suggested that the CTD sensor was accurate to within 0.1 decibars. 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;

    All stations: dP = 0.7 decibars


The platinum resistance temperature sensor fitted to the CTD unit was calibrated against platinum resistance thermometers on 15/01/2002 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 = -4.769 * 10-10; b = -1.428 * 10-4; c = 3.289 * 10-3

This is equivalent to a correction of between 1 and 3 m°C in the range 4 - 14 °C.

One pair of digital reversing thermometers were used during the cruise fitted to a Niskin water sampling bottle fired close to the seabed. The mean difference between the reversing thermometers and the CTD temperature sensor of -10 m°C is within the expected tolerance of the CTD and the thermometers.


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

    All stations: a = 6.2854 * 10-6; b = -2.8213 * 10-7; c = 1.0004639

Using these coefficients the root mean square difference between the water sample (salinometer) alinities and the corrected CTD salinities is 0.002 (60 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 operated on one range throughout the cruise (x10 gain) 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 21-53, 153-181: a = 2.033; b = -0.36; R2 = 0.91; Number of samples = 43

    Stations 70-103: a = 2.647; b = -0.55; R2 = 0.72; Number of samples = 15

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 21-28, 153-181: a = 106.38; b = -2.72; R2 = 0.94; Number of samples = 41

    Stations 31-53: a = 101.01; b = -0.05; R2 = 0.98; Number of samples = 12

    Stations 70-103: a = 81.97; b = 0.58; R2 = 0.98; Number of samples = 15

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.

Originator's Note Concerning Series 741399

The 1 decibar binned profile has two density inversions in the upper 10 metres, one of about 0.02 kg m-3 and one of about 0.07 kg m-3. The site of this cast is the Lune Deep, 6 kilometres from the coast. During the previous 12 hours winds from the South-South-West of 40 knots were recorded. In these circumstances, it is not unreasonable to expect some disturbance to the upper levels of the water column. Furthermore, the salinity minimum at 9 decibars pressure which gives rise to the more pronounced inversion was observed in both the CTD up- and downcasts.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information


Cruise Name CIR1X/02
Departure Date 2002-01-16
Arrival Date 2002-01-28
Principal Scientist(s)David Brian Sivyer (Centre for Environment, Fisheries and Aquaculture Science Lowestoft 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