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Metadata Report for BODC Series Reference Number 748509


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Seapoint Turbidity Meter  optical backscatter sensors
Seapoint chlorophyll fluorometer  fluorometers
LI-COR LI-192 PAR sensor  radiometers
Falmouth Scientific Instruments NXIC CTD Series  CTD; water temperature sensor; salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Liam Fernand
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 CO05/04/1
BODC Series Reference 748509
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2004-05-18 11:34
End Time (yyyy-mm-dd hh:mm) 2004-05-18 11:52
Nominal Cycle Interval 0.1 decibars
 

Spatial Co-ordinates

Latitude 51.99150 N ( 51° 59.5' N )
Longitude 2.08333 E ( 2° 5.0' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 3.4 m
Maximum Sensor or Sampling Depth 29.9 m
Minimum Sensor or Sampling Height 0.1 m
Maximum Sensor or Sampling Height 26.6 m
Sea Floor Depth 30.0 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 Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODERankUnitsTitle
ACYCAA011DimensionlessSequence number
CPHLPS011Milligrams 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 and calibration against sample data
FVLTWS011VoltsRaw signal (voltage) of instrument output by linear-response chlorophyll fluorometer
IRRDUV011MicroEinsteins per square metre per secondDownwelling vector irradiance as photons of electromagnetic radiation (PAR wavelengths) in the water body by cosine-collector radiometer
LVLTLD011VoltsRaw signal (voltage) of instrument output by cosine-collector downwelling PAR radiometer
NVLTSP011VoltsRaw signal (voltage) of instrument output by SeaPoint turbidity meter
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PPSBZZ011MetresDepth below surface of the water body by unknown instrument and correction to zero at sea level and conversion to depth using unspecified 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
TEMPCC011Degrees CelsiusTemperature of the water body by CTD and verification against independent measurements
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

IRRDUV01 and LVLTLD01: Photosynthetically Active Radiation sensor was malfunctioning data is not reliable. Increasing light irradiation with depth.


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

RV CORYSTES: CRUISE 5/04: CTD data document

Sampling strategy

A total of 22 CTD profiles were obtained. CTD were deployed at West Gabbard and at the Warp.

For further detail refer to the cruise report.

Instrument Description

Instrumentation and data processing

The CTD used was a Falmouth Scientific Inc, serial number 1351. Samples were collected for salinity analysis (using a Guildline salinometer) to derive a calibration for the instrument conductivity sensor. A pair of digital reversing thermometers were used to compare with the CTD temperature estimates. A CHELSEA fluorometer and SEAPOINT turbidity sensor were used at all CTD stations. A LICOR photosynthetically-active- radiation sensor (with a six-decade log amplifier) was fitted to the rosette at all CTD stations. Chlorophyll samples were collected to calibrate the fluorometer and samples for suspended particulate matter analysis were used to calibrate the turbidity sensor.

A list of calibrated parameters and instrumentation used is shown below.

Measurement Parameter Units Instrumentation Calibration
pres Pressure dbar Not listed Corrected from deck measurements
temp Temperature °C Temperature sensor Calibrated from Platinum resistance thermometers (PRT's) March 2004
salinity Salinity n/a Guildline Salinometer Calibrated against bottle samples
turb Turbidity volts Seapoint Turbidity sensor Calibrated against bottle samples
sl Suspended Load mg/L Seapoint Turbidity sensor Used to calibrate turbidity
light Light volts Licor Light sensor (s/n 5672) Used to calculate PAR
fluor Fluorescence volts Seapoint Fluorometer Calibrated against bottle samples

Change of sensors during cruise: None reported.

The data sets were calibration by CEFAS:

(a) Pressure

During the cruise the 'on deck' CTD pressure immediately prior to lowering the CTD was recorded. These 'on deck' observations have been used to correct recorded CTD pressure as follows:

P(cor) = P(unc) + dP

Station Pctd on deck
1 0.6
4 0.55
6 0.55
7 0.51
10 0.49
11 0.48
13 0.55
14 0.53
16 0.53
18 0.5
19 0.5
21 0.5
24 0.5
27 0.5
29 0.51
30 0.51
31 0.46
32 0.49
Mean 5.1

dp = -0.51 was used in the CTD (pressure sensor) calibration

(b) Temperature

The Platinum Resistance Thermometer (PRT) temperature sensor fitted to CTD 1366 was calibrated using PRT's during March 2004, and this was used to correct the CTD temperature :

T(cor) = T(unc) + dT

dT = a*T(unc)*T(unc) + b*T(unc) + c

where

a = -5.22e-5 b= 6.47e-4 c= -1.03e-3 for s/n 1366

(c) Conductivity

For this cruise it is assumed that the tolerance between salinity (water samples) and CTD (salinity) is accurate to 0.1 plus the manufacturer tolerance of 0.003. Most of the stations for CTD s/n 1351B, 1366B and 1397B are within the required tolerance. All CTD readings not within this tolerance have not been used for any calculations. Salinometer reading takes precedence over the CTD reading.

A least square fit was used to determine appropriate calibration coefficients:

CR(cor) = CR(ctd) [a*T(cor) + b*P(cor) + c]

where T(cor) and P(cor) are the corrected CTD temperature and pressure and

s/n 1366B

a -6.816E-05

b -2.38E-06

c 1.00116425

Using these coefficients the rms difference between water sample (salinometer) and corrected CTD salinity for s/n 1366B is 0.007 (40 values).

d) Suspended Load - Turbidity Sensor Calibration

The Seapoint turbidity sensor (s/n 1609) was calibrated by comparing recorded voltages with samples collected (during ascent of the CTD) for suspended load analysis

suspended load (mg/l) = a * Turbidity (volts) + b

where

a = 4.525E+01 b = -0.381E+01 R2 = 0.2314 (for stations 1 - 35)

e) Fluorometer - Chlorophyll Calibration

A Seapoint fluorometer (s/n 2359) was fitted to the rosette sampler and used to estimate chlorophyll levels. The sensor was calibrated by comparing recorded voltages with measured chlorophyll of samples collected in niskin bottles as the CTD rosette returned to the surface.

Chlorophyll (ug/l) = a*Fluorometer (volts) + b

a = 18.76 b = -1.848 R2 = 0.5303 (for stations 1-35)

f) Photosynthetically Active Radiation

The Licor light sensor (s/n 5672) was calibrated according to the LiCor Amplifier and Sensor calibrations which gave overall factors for calculating uE s-1 m-2.

Offset X=3.44824

L.C=0.170237

BODC post-processing and screening

Reformatting

Data for the 22 CTD casts were provided in ASCII format as .cor files. These were reformatted to the internal QXF format using a BODC transfer function, to allow the use of in-house visualisation tools. Variables within the .cor files were mapped to appropriate BODC parameter codes:

Parameters such as Specific Volume Anomaly (SVAN) and Brunt Wiesler frequency (bvf) were not transferred as they are not considered environmentally measured and can be readily reproduced from the other data.

Screening

Reformatted CTD data were visualised using the in-house editor EDSERPLO. EDSERPLO provides a graphical representation of the data so that parameters can be screened and checked for abnormalities. All parameters were plotted against pressure. Checks include identifying data spikes, gaps in the data and values that lie outside of expected limits for the environment. No data values were deleted. Flagging was achieved by modification of the associated quality control flag.

Falmouth Scientific NXIC CTD Series

The FSI NXIC CTD Series is a collection of rugged Conductivity-Temperature-Depth profilers that utilise the patented Non-eXternal Inductive Cell (NXIC) conductivity sensor, which was originally developed for the US Navy DT-705 Sound Velocity/Salinity sensor. The CTDs are fast sampling, fully integrated instruments with optional battery power, datalogging and external analog sensor input.

Models in the collection include the NXIC CT Bio Direct Read-500M, NXIC CTD Bio Direct Read-500M, NXIC CTD Bio Auto-500M, NXIC CTD Direct Read-500M, NXIC CTD Direct Read-700M, NXIC CTD Auto-500M, NXIC CTD Auto-700M, NXIC CTD-ADC with external sensors, and the NXIC ETSG Thermosalinograph. Parameters are measured to an accuracy ranging from 0.002-0.010 mS/cm for conductivity, 0.005 degC for temperature and 0.08% for full scale pressure. Now marketed by Teledyne RD Instruments.

Specifications

  Conductivity Temperature Pressure
Sensor type Inductive cell Thermistor Precision-machined Silicon
Range 0 to 9.0 S m-1 -5 to 45°C user specified
Accuracy ± 0.0002 S m-1 ± 0.005°C 0.08 % full scale
Stability ± 0.00005 S cm-1 month-1 0.0005°C month-1 ± 0.004 %
Resolution 0.00001 S m-1 0.001°C 0.001 % full scale
Response 5.0 cm at 1 m sec-1 flow 100 msec 25 msec

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

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.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name COR5/04
Departure Date 2004-05-18
Arrival Date 2004-05-19
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

Fixed Station Information

Station NameWest Gabbard
CategoryOffshore location
Latitude51° 59.00' N
Longitude2° 5.00' E
Water depth below MSL32.0 m

Fixed Station Information

Station Name West Gabbard
Category Offshore area
Latitude 51°59' N
Longitude 002°05'E
Water depth 32 m

This deployment form part of the National Marine Monitoring Programme (NMMP) funded by the UK Government's Department for Environment, Food and Rural Affairs (Defra)

The West Gabbard SmartBuoy has been at its present location in the southern North Sea since August 2002. Its position is also one of the first WaveNet locations in approximately 32 m water depth.

The SmartBuoy is used to observe the dynamics of plant nutrients and the growth of phytoplankton. Measurements of plant nutrient concentrations are derived from two SmartBuoy instruments. Hourly measurements of nitrate concentration are made by the NAS2E in situ nutrient analyser, while lower frequency (daily) measurements of nitrate and silicate concentration are derived from laboratory analysis of water samples collected and preserved by the AquaMonitor.

Phytoplankton concentration (biomass) is measured 4 times per hour using a fluorometer measuring chlorophyll fluorescence. To aid interpretation of these data, SmartBuoy also takes measurements of conductivity, temperature, suspended sediment concentration and light penetration.

Related Fixed Station activities are detailed in Appendix 1


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

Appendix 1: West Gabbard

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Series IdentifierData CategoryStart date/timeStart positionCruise
748510CTD or STD cast2004-05-18 13:01:0051.986 N, 2.09217 ERV Corystes COR5/04
748522CTD or STD cast2004-05-18 13:59:0051.99367 N, 2.08833 ERV Corystes COR5/04
748534CTD or STD cast2004-05-18 15:01:0051.984 N, 2.08117 ERV Corystes COR5/04
748546CTD or STD cast2004-05-18 16:00:0051.9825 N, 2.08967 ERV Corystes COR5/04
748558CTD or STD cast2004-05-18 17:05:0051.984 N, 2.0905 ERV Corystes COR5/04
748571CTD or STD cast2004-05-18 18:02:0051.98367 N, 2.092 ERV Corystes COR5/04
748583CTD or STD cast2004-05-18 19:01:0051.9835 N, 2.09033 ERV Corystes COR5/04