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Metadata Report for BODC Series Reference Number 742157


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
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 lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Al Joyce
Originating Organization 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 CO11/03/122
BODC Series Reference 742157
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2003-08-19 10:43
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars
 

Spatial Co-ordinates

Latitude 49.66567 N ( 49° 39.9' N )
Longitude 6.29917 W ( 6° 18.0' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 3.0 m
Maximum Sensor or Sampling Depth 103.0 m
Minimum Sensor or Sampling Height 2.0 m
Maximum Sensor or Sampling Height 102.0 m
Sea Floor Depth 105.0 m
Sea Floor Depth Source DATAHEAD
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 -
 

Parameters

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
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

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

COR11/03 CTD Instrument Description

Instrument Type Manufacturer and Model Serial Number Manufacturer's Description Available?
CTD Falmouth Scientific Inc. CTD 1366 and 1322 No
Light Sensor LICOR 5672 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).

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.

COR11/03 CTD Originator's Data Processing

Sampling strategy

A total of 70 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. Samples for suspended particulate matter analysis were used to calibrate the turbidity sensor.

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 1322: dP = 0.4 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 01/01/2003 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 1322: a = -4.2313 * 10-5; b = 5.3137 * 10-4; c = 5.223 * 10-4

    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 -6 m°C in the range 13 - 20 °C for S/N 1322 and -10 - -2 m°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 1322: a = -1.8831437 * 10-5; b = -2.6107679 * 10-7; c = 1.0002349

    S/N 1366: a = -2.7020413 * 10-5; b = -8.2163621 * 10-7; c = 1.0000295

Using these coefficients, the root mean squared difference between the water sample (salinometer) and corrected CTD salinity for S/N 1366 is 0.004 (8 samples) and for S/N 1322 is 0.004 (108 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 4, 21, 151, 193-317: a = 0.843; b = -0.083; R2 = 0.926; Number of samples = 111

    Stations 36, 54, 60, 72, 74, 90, 92: a = 1.099; b = -0.213; R2 = 0.937; Number of samples = 16

    Stations 37-53, 55-59, 61-71, 73, 75-89, 91, 93-100: a = 0.579; b = 0.039; R2 = 0.927; Number of samples = 80

    Stations 160-187: a = 0.694; b = -0.029; R2 = 0.976; Number of samples = 16

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

    All stations: a = 3.0883; b = 0.365; R2 = 0.9861; Number of samples = 8

The sensor only logged correctly at stations 2 to 21. A problem with the extra channel circuitry of CTD S/N 1322 appears to have prevented the sensor records from being logged correctly at the other stations.

Photosynthetically Active Radiation

The LICOR light sensor used to measure photosynthetically active radiation was calibrated during January 2002 using a standard lamp. This gave an in-air current equivalent to 0.3495 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 COR11/03
Departure Date 2003-08-14
Arrival Date 2003-08-27
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