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Metadata Report for BODC Series Reference Number 969516

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
SeaTech transmissometer  transmissometers
Sea-Bird SBE 13 Dissolved Oxygen Sensor  dissolved gas sensors
Sequoia Laser In-Situ Sediment Size Transmissometer  transmissometers; water temperature sensor; in-situ particle sizers
Sea-Bird SBE 911plus CTD  CTD; water temperature sensor; salinity sensor
LI-COR LI-192 PAR sensor  radiometers
Turner Designs SCUFA II Submersible Fluorometer  fluorometers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Alex Souza
Originating Organization Proudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) POL Dee Experiment

Data Identifiers

Originator's Identifier C001
BODC Series Reference 969516

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2007-03-13 09:54
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 0.5 decibars

Spatial Co-ordinates

Latitude 53.45017 N ( 53° 27.0' N )
Longitude 3.50117 W ( 3° 30.1' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 1.73 m
Maximum Sensor or Sampling Depth 14.12 m
Minimum Sensor or Sampling Height 2.88 m
Maximum Sensor or Sampling Height 15.27 m
Sea Floor Depth 17.0 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


BODC CODERankUnitsTitle
ATTNMR011per metreAttenuation (red light wavelength) per unit length of the water body by 20 or 25cm path length transmissometer
DOXYPR011Micromoles per litreConcentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ Beckmann probe
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
NVLTLS011VoltsRaw signal (voltage) of instrument output by LISST scatterometer
OXYSBB011PercentSaturation of oxygen {O2 CAS 7782-44-7} in the water body [dissolved plus reactive particulate phase] by in-situ Beckmann probe and computation from concentration using Benson and Krause algorithm
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
SIGTPR011Kilograms per cubic metreSigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPCC011Degrees CelsiusTemperature of the water body by CTD and verification against independent measurements
TVLTZR011VoltsRaw signal (voltage) of instrument output by red light transmissometer

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

Problem Report

Dissolved Oxygen

All data from this channel should be used with caution as the values measured were unrealistic during this and several other cruises. Readings taken by the probe indicated that the sensor was constantly saturated. It is advised that the data should only be used for relative comparisons.

Data quality notes

LISST transmission and scattering

Users should be aware that the clear water values measured on different cruises are observed to increase and decrease at times, which is not consistent behaviour. In addition, the clear water scattering values are also sometimes less than and sometimes greater than those measured by the manufacturer at the time of last calibration (October 2006). This may be due to a problem with the instrument or the method in which the clear water values are measured.

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Sea Bird Electronics SBE13 Dissolved Oxygen Sensor

The SBE 13 was designed as an auxiliary sensor for Sea Bird SBE 9plus, but can fitted in custom instrumentation applications. When used with the SBE 9 Underwater Unit, a flow-through plenum improves the data quality, as the pumping water over the sensor membrane reduces the errors caused by oxygen depletion during the periods of slow or intermittent flushing and also reduces exposure to biofouling.

The output voltage is proportional to membrane current (oxygen current) and to the sensor element's membrane temperature (oxygen temperature), which is used for internal temperature compensation.

Two versions of the SBE 13 are available: the SBE 13Y uses a YSI polarographic element with replaceable membranes to provide in situ measurements up to 2000 m depth and the SBE 13B uses a Beckman polarographic element to provide in situ measurements up to 10500 m depth, depending on the sensor casing. This sensor includes a replaceable sealed electrolyte membrane cartridge.

The SBE 13 instrument has been out of production since 2001 and has been superseded by the SBE 43.


Measurement range 0 to 15 mL L-1
Accuracy 0.1 mL L-1
Time response

2 s at 25°C

5 s at 0°C

Depth range

2000 m (SBE 13Y- housing in anodized aluminum)

6800 m (SBE 13B- housing in anodized aluminum)

105000 m (SBE 13B- housing in titanium)

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

Prince Madog Cruise PD04_07 CTD Instrumentation

The CTD unit was a Sea-Bird Electronics 911plus system (SN P23655-0620), with dissolved oxygen sensor. The rosette sampling system was equipped with 5 litre sampling bottles (manufactured by Ocean Test Equipmetn Inc.). In addition the CTD was fitted with a red (660 nm) beam transmissometer, a fluorometer, a Sequoia Scientific Laser In-Situ Scattering and Transmissometry (LISST) particle analyser and a LI-COR Underwater Quantum Sensor. The Sea-Bird sensors SBE 3,4 and 13 Beckman were last calibrated by the manufacturer in January 2004. Also attached was a Sea-Bird SBE-35 Temperature Logger to supply an independent check of temperature. The table below lists more detailed information about the various sensors.

Sensor Model Serial Number Calibration Date Comments
Pressure transducer Paroscientific Digiquartz 42A-105 76076 21/01/2004 -
Conductivity sensor SBE 4 2543 14/01/2004 -
Temperature sensor SBE 3 P4100 21/01/2004 -
Dissolved oxygen SBE 13 Beckman 130580 05/01/2004 -
Transmissometer 660nm SeaTech T1000 T1021 03/03/1998 0.2 m path length
Fluorometer Turner SCUFA II 262 - -
LISST 25 120 26/10/2006 Range 1.25 to 250 µm
LI-COR LI 192SB 33 - -
Temperature Logger SBE-35 0041 - -

Change of sensors during cruise: None reported.

Water sampling device

Rosette sampling system equipped with 5 litre sampling bottles, manufactured by Ocean Test Equipment Inc.

Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers

The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.

Underwater unit

The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.

Temperature, conductivity and pressure sensors

The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.

The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

Additional sensors

Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.

Deck unit or SEARAM

Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.


Specifications for the SBE 9 plus underwater unit are listed below:

Parameter Range Initial accuracy Resolution at 24 Hz Response time
Temperature -5 to 35°C 0.001°C 0.0002°C 0.065 sec
Conductivity 0 to 7 S m-1 0.0003 S m-1 0.00004 S m-1 0.065 sec (pumped)
Pressure 0 to full scale (1400, 2000, 4200, 6800 or 10500 m) 0.015% of full scale 0.001% of full scale 0.015 sec

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

Turner Designs Self-Contained Underwater Fluorescence Apparatus (SCUFA)

The Turner Designs SCUFA is a submersible fluorometer for chlorophyll and dye tracing operations that has been designed to operate in a wide range of concentrations, environmental conditions as well as operational modes (profiling or moored deployments). The instrument includes an integrated temperature probe and software which allow for automatic correction of fluorescence data from temperature effects. The superior ambient light rejection eliminates the effects of sunlight and allows the SCUFA to be used in surface waters without the need for external pumps or light shields.

Each instrument can be customised to meet user requirements. Users can choose one of the following channels: chlorophyll a, cyanobacteria (phycocyanin or phycoerythrin pigments), rhodamine WT, fluorescein and turbidity. Instrument options include turbidity, internal data logging and automatic temperature correction.

Three versions of the SCUFA are available: SCUFA I, II and III. SCUFA I and II are used for chlorophyll a applications, while SCUFA III is used for Rhodamine WT. Models II and III include a turbidity channel that is not present on model I. The SCUFA has been out of production since 2008.


Depth rating 600 m
Detector Photodiode
Temperature range -2 to 40°C
Maximum sampling rate

1Hz- digital

5 Hz- analog


12 bit- digital

1.2 mV- analog

Dynamic Range
Fluorescence 4 orders of magnitude
Turbidity 3 orders of magnitude

The table below presents the specifications for the different channels.

Specifications Chlorophyll Cyanobacteria Rhodamine WT/Fluorescein
Light source Blue

Orange- PC

Blue- PE

Excitation/Emission 460/685

595/670 (phycocyanin, PC)

528/573 (phycoerythrin, PE)

530/600 (rhodamine)

490/580 (fluorescein)

Minimum detection Limit
Fluorescence 0.02 µg L-1 150 cells mL-1 0.04 ppb
Turbidity 0.05 NTU 0.05 NTU 0.05 NTU

Further details can be found in the manufacturer's brochure.

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).

SeaTech Transmissometer


The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.


  • Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
  • Beam diameter: 15 mm
  • Transmitted beam collimation: <3 milliradians
  • Receiver acceptance angle (in water): <18 milliradians
  • Light source wavelength: usually (but not exclusively) 660 nm (red light)


The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.

A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.

Further details can be found in the manufacturer's Manual.

Sequoia Laser In-situ Sediment Size Transmissometer (LISST)

The Sequoia LISST measures particle size distribution of suspended sediments by laser diffraction. This technique allows particles of various compositions to be measured with a single device and, because the particle volume is roughly of the same order for all sizes, the required dynamic range of the sensors is reduced compared with single-particle counters.

The instrument includes optics for producing a collimated laser beam, a detector array, electronics for signal amplification and processing, a data storage and scheduling computer and a battery system. The primary measurement is the scattering of laser light at a number of angles, which is mathematically inverted to give a grain size distribution, and also scaled to obtain the volume scattering function. The size distribution is presented as concentration in each of 32 logarithmically-spaced grain-size class bins. Optical transmission, water depth and temperature are recorded as supporting measurements.

Several models are available and although the principals of operation are the same, their specifications vary slightly. The specifications for model LISST-100 are provided below.


Optical path length

5 cm (standard)

2.5 cm (optional)

Optical transmission 12 bit resolution
Particle size range

Type B: 1.25 to 250 micron diameter

Type C: 2.5 to 500 micron diameter

Resolution 32 size classes, log-spaced
VSF angle range 1.7 to 340 mrad
Maximum sample speed 4 size distributions per second (standard)
Temperature range -10 to 45 °C
Temperature resolution 0.01 °C
Pressure range 0 to 300 m
Pressure resolution 8 cm

Further details can be found in the manufacturer's manual.

Prince Madog Cruise PD04_07 CTD Processing

Sampling Strategy

A total of 103 CTD casts were performed during the cruise. 2 stations were sampled in Liverpool Bay and remaining sampling was carried out over two 25 hour tidal cycles in the Welsh and Hilbre Channels in the Dee Estuary. Rosette bottles were fired near-bed on numerous profiles in order to obtain independent temperature and salinity samples. Water bottle samples were also taken from the near-surface and near-bed bottle for filtering to determine suspended sediment load, by the School of Ocean Sciences.

Data were logged at 24 Hz onto a PC running SEASAVE, Sea-Bird's data acquisition software. It should be noted, however, that the CTD PC logging and operating system suffered technical difficulties throughout this cruise. As a result, full downcast and full upcast data are available for only 61 of 103 casts. Full downcast and partial upcast data are available for 16 casts. There are also 26 casts where only the downcast was successfully recorded. The raw Sea-Bird data, configuration and bottle files were supplied to BODC for further processing.

BODC post-processing and screening

Sea-Bird Processing

The raw CTD files were processed through the Sea-Bird SBE Data Processing software version 5.35. Binary (.DAT) files were converted to engineering units and ASCII format (.CNV) using the DATCNV program.

Sea-Bird software program ALIGNCTD was run to advance conductivity by 0s and oxygen by 3s (within the typical range given in the Sea-Bird manual). No adjustment was made to the temperature channel as the fast sensor response time renders this unnecessary, according to the Sea-Bird literature.

To compensate for conductivity cell thermal mass effects, the data files were run through CELLTM, using alpha = 0.03, 1/beta = 7, typical values for this CTD model given in the Sea-Bird literature. After running WILD EDIT, FILTER was run on the pressure channel using the recommended time filter of 0.15 seconds. Next, a minimum CTD velocity of 0.0 m s-1 was used for LOOP EDIT in order to exclude scans where the CTD was travelling backwards due to ship's heave. Salinity, density and oxygen concentration were then calculated and added to the output files using the DERIVE program. The files were then averaged to 0.5 second intervals using BINAVERAGE.


The data were converted from ASCII format into BODC internal format (QXF). The following table shows the mapping of variables within the original files to appropriate BODC parameter codes:

Originator's Variable Units Description BODC Parameter Code Units Comments
Pressure, Digiquartz dbar Pressure exerted by the water body PRESPR01 dbar -
Oxygen, Beckman/YSI ml l-1 Dissolved oxygen concentration from Beckman probe DOXYPR01 µmol l-1 Converted from ml l-1 to °mol l-1 by multiplying the original value by 44.66
Salinity - Practical salinity of the water body by CTD PSALCU01 - Generated by Sea-Bird software from CTD temperature and conductivity data
Temperature [ITS-90] °C Temperature of the water column by CTD TEMPCU01 °C -
Voltage 2 Un-adjusted volts Voltage from CTD PAR Sensor LVLTD01 Un-adjusted volts -
Voltage 3 Un-adjusted volts Beam transmissometer voltage TVLTCR01 Un-adjusted volts -
Voltage 4 Un-adjusted voltd Voltage from CTD SCUFA Turner fluorometer FVLTWS01 Un-adjusted volts -
Voltage 6 Un-adjusted volts LISST scatterometer voltage output NVLTLS01 Un-adjusted volts -
Voltage 7 Un-adjusted volts LISST transmissometer voltage output TVLTZR01 Un-adjusted volts -
- - Potential Temperature POTMCV01 °C Generated at BODC using UNESCO Report 38(1981) algorithm with parameters PSALCC01 and TEMPCC01
- - Sigma-theta SIGTPR01 Kg m-3 Generated at BODC using Fofonoff and Millard (1982) algorithm
- - Beam Attenuation ATTNMR01 m-1 Generated at BODC from calibrations of TVLTCR01
- - PAR IRRDUV01 µEm-2s-1 Generated at BODC from calibration of LVLTLD01
- - Salinity PSALCC01 - Generated at BODC from calibration of PSALCU01
- - Temperature TEMPCC01 °C Generated at BODC from calibration of TEMPCU01
- - Oxygen Saturation OXYSBB01 % Generated at BODC during transfer using the Benson and Krause (1984) algorithm

Reformatted CTD data were transferred onto a graphics work station for visualisation using the in-house editor Edserplo. Data that were considered unrealistic were flagged as suspect.

Once quality control screening was complete, the CTD downcasts were banked. Finally, the data were binned against pressure at 0.5 dbar increments.



37 independent salinity samples, obtained from the CTD rosette, were used to calibrate the CTD. 3 points were deemed to be outliers (casts C021, C027 and C051) and were removed from the analysis. The salinity offset (bottle salinity - CTD salinity) was examined to see if it varied with pressure or bottle salinity. Significant relationships at 95% confidence were found between offset and bottle salinity (R2=37.3%). A calibration equation was derived from the relationship between mean offset and bottle salinity as follows, based on 34 observations: calibrated salinity = CTD salinity * 1.14417 - 4.5881.

The calibration residuals ranged from -0.191 to 0.3301. The mean offset of the dataset with outliers removed is -0.1031


93 independent temperature values were compared to pressure and CTD temperature. 1 point was identified as an outlier (cast C063 at depth 1.104m) and was removed from the analysis. The offset between CTD temperature and SBE-35 temperature was found not to be significantly different from zero at 95% confidence. Therefore, there was no adjustment to the CTD temperature resulting from the application of manufacturer's coefficients during initial processing.

The mean offset with the outlier removed is -0.0018


There were no casts where the CTD was logging in air, so it was not possible to determine a pressure offset. No adjustments were made to the values resulting from application of manufacturer's coefficients during the intial processing.

Beam attenuation

Coefficients M and B were calculated, allowing calibration of the transmissometer with air readings taken during the cruise. M and B are calculated according to SBE Application Note No. 7:

M = (Tw/W0)*(A0-Y0)/(A1-Y1)
B= -M*Y1

Where Tw is the percent transmission for pure water for the instrument (92.98%); W0 is the voltage output in pure water (4.649 volts); A0 is the manufacturer's air voltage (4.661 volts); Y0 is the manufacturer's blocked path voltage (0.000 volts); A1 is the cruise maximum air voltage (4.526 volts); Y1 is the current blocked path voltage (0.0000 volts). For this cruise, M and B were calculated to be 20.5966 and 0, respectively.

M and B are then inserted into the following equations (from SBE Application Note No. 7) to obtain calibrated beam attenuation: Light transmission [%] = (M * voltage output) + B Beam attenuation coefficient c = - (1/z) * ln (light transmission [decimal])

Where M and B are the calibration coefficients, z is the transmissometer path length (0.2m), light transmission[decimal] is light transmission [%] divided by 100, c = beam attenuation (m-1)

Dissolved oxygen

The data are uncalibrated, as there were no field samples taken for calibration.


The data are uncalibrated, as there were no field samples taken for calibration.

LISST transmission and scattering

The data are currently uncalibrated. However, the voltages can be calibrated to give optical transmission, beam attenuation, total volume concentration and Sauter mean diameter according to the following manufacturer's constants and calculations:

Optical Transmission = b = (VT-VToff)/(VTO-VToff)

Beam attenuation = -ln(b)/0.025 - units are metres-1, assumes 25 mm path

Total volume concentration = TV = cal*[((VS-VSoff)/b)-(VSO-VSoff)] - units are µl l-1

Sauter mean diameter = SMD = a*[TV/(-ln(b)] - units are µm

Where cal = total volume concentration calibration constant = 160, a = Sauter mean diameter calibration constant = 0.09, VSO = clearwater scattering output = 0.150 V (see note below), VTO = clear water transmission output = 3.215 V (see note below), VSoff = scattering output offset = 0.10 V, VToff = transmission output offset = 0.10 V. Measured outputs are scattering = VS and transmission = VT.

N.B. The clear water values quoted above are supplied by the manufacturer. Ideally these should be replaced by values determined by the LISST calibration cast, during which the instrument is placed in a tank of clean water. However, there is suspicion that these values may not be accurate. There are abnormally high values for some cruises, which the manufacturer suggests may be due to the calibration dip occurring in insufficiently clear water. Therefore, manufacturer's values have been quoted along with values measured by the instrument during previous cruises. Users are advised to use their own discretion in deciding which coefficients to apply.

Date Cruise VT0 VS0
24/02/2004 PD06_04 3.292 0.442
02/03/2004 PD07_04 3.266 0.447
29/03/2004 PD11_04 3.357 0.447
10/05/2004 PD18_04 3.867 0.867
20/07/2004 PD29_04 3.501 0.468
10/08/2004 PD32_04 3.730 0.701
28/10/2004 PD48_04 3.372 0.459
14/12/2004 PD52_04 3.330 0.428
30/01/2005 PD02_05/PD03_05 3.319 0.469
28/02/2005 PD07_05 3.280 0.465
05/04/2005 PD11_05 3.299 0.455
10/05/2005 PD18_05 3.365 0.460
14/06/2005 PD21_05 3.371 0.479
13/07/2005 PD25_05 3.415 0.486
16/08/2005 PD30_05 3.171 0.463
14/09/2005 PD34_05 3.156 0.471
26/10/2005 PD41_05 3.145 0.442
13/12/2005 PD48_05 2.957 0.463
05/02/2006 PD04_06/PD05_06 3.071 0.523
05/03/2006 PD09_06 3.156 0.611
04/04/2006 PD12_06 2.969 0.447
08/05/2006 PD16_06 2.904 0.446
12/12/2006 PD37_06 2.723 0.156
12/02/2007 PD02_07 2.74 0.154
12/03/2007 PD04_07 2.672 0.17


During instrument deployment, no effort was made to avoid data collection possibly being affected by ship shadowing. The LI-COR LI 192SB sensor number 33 was calibrated from raw voltages using the CEFAS supplied equation: PAR = 0.157508*exp(volts*3.42410)


Benson, B. B. and Krause, D., 1984. The concentration and isotopuc fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanogr., 29(3),620-632

Fofonoff, N. P. and Millard, R. C., 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science No. 44, 53pp.

UNESCO, 1981.Background papers and supporting data on the International Equation of State of Seawater 1980. UNESCO Technical Papers in Marine Science No. 38, 192pp.

Project Information

Proudman Oceanographic Laboratory Dee Experiment


Sediment transport process models are a vital tool in allowing scientists to predict sediment transport and forecast seabed and coastal morphodynamic evolution. It is however, difficult to obtain accurate models due to the complex inter-dependence of sediment processes in the bottom boundary layer. This inter-dependence is governed by interactions between the sediment transport triad; the bed, the hydrodynamics and the mobile sediments.

Scientific Objectives

  • To use a varying suite of instruments to make co-located measurements of the sediment triad
  • To provide a framework to allow assessment and improvement of the latest sediment transport models
  • To address dynamics of suspended sediments in terms of supply of material to the coastal zone from estuaries
  • Development of a new description of suspended sediment and water opacity to improve simulation of coastal primary productivity


The study site chosen by POL for this research was the Dee Estuary, Liverpool Bay. POL performed fieldwork in the Hilbre Channel on the eastern side of the Estuary and the Welsh Channel on the western exit of the Estuary, with emphasis placed on two repeat stations, HC and WC. The fieldwork started in February 2005 and has been summarised below:

Cruise Dates Hilbre Channel Welsh Channel
PD03_05 2005-02-03 to 2005-02-04 25 hour CTD station
3 x mooring deployments
13 hour CTD station
1 mooring deployment
PD07_05 2005-03-03 to 2005-03-04 23 hour CTD station
Mooring recovery
19 hour CTD station
Mooring recovery
PD05_06 2006-02-08 to 2006-02-10 24 hour CTD station
2 x mooring deployment
22 hour CTD station
1 mooring deployment
PD09_06 2006-03-06 to 2006-03-09 23 hour CTD station
Mooring recovery
25 hour CTD station
Mooring recovery
PD04_07 2007-03-13 to 2007-03-16 25 hour CTD station
2 x mooring deployment
25 hour CTD station
1 mooring deployment


The Dee Experiment project was core funded by POL under Programme 2 (Shallow coastal seas) Theme 5 (Coastal and sediment processes) of POL's Science Programme 2001 - 2006. From March 2007 onwards, this core funding was replaced by funding from NERC's Oceans 2025 programme and the Dee Experiment research continued as part of Oceans 2025 Work Package 3.3.

Data Activity or Cruise Information


Cruise Name PD04/07
Departure Date 2007-03-13
Arrival Date 2007-03-16
Principal Scientist(s)Alejandro J Souza (Proudman Oceanographic Laboratory)
Ship RV Prince Madog

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