Metadata Report for BODC Series Reference Number 1030460

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
SeaTech transmissometer  transmissometers
Sea-Bird SBE 43 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 Mr John Howarth
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) Coastal Observatory
Oceans 2025
Oceans 2025 Theme 10 SO11

Data Identifiers

Originator's Identifier CTD010
BODC Series Reference 1030460

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-01-26 21:38
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 0.2 decibars

Spatial Co-ordinates

Latitude 53.69783 N ( 53° 41.9' N )
Longitude 3.91717 W ( 3° 55.0' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 1.29 m
Maximum Sensor or Sampling Depth 39.74 m
Minimum Sensor or Sampling Height 2.65 m
Maximum Sensor or Sampling Height 41.11 m
Sea Floor Depth 42.4 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
DOXYSU011Micromoles per litreConcentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and no 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
NVLTLS011VoltsRaw signal (voltage) of instrument output by LISST scatterometer
OXYSSU011PercentSaturation of oxygen {O2 CAS 7782-44-7} in the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor 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

No Problem Report Found in the Database

Prince Madog Cruise PD02_10 Data Quality Report

Data Quality Report

LISST Channels NVLTLS01 and TVLTZR01

LISST data from the following casts have been compromised by the presence of steep density gradients and data should be used with caution: CTD005 and CTD015-CTD018.

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 Dissolved Oxygen Sensor SBE 43 and SBE 43F

The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.

Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.


Housing Plastic or titanium

0.5 mil- fast response, typical for profile applications

1 mil- slower response, typical for moored applications

Depth rating

600 m (plastic) or 7000 m (titanium)

10500 m titanium housing available on request

Measurement range 120% of surface saturation
Initial accuracy 2% of saturation
Typical stability 0.5% per 1000 h

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

Prince Madog Cruise PD02_10 CTD Instrumentation

The CTD unit was a Sea-Bird Electronics 911plus system (SN P23655-0620), with dissolved oxygen sensor. 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. Also attached was a Sea-Bird SBE 35 Temperature Logger to supply an independent check of temperature. All instruments were attached to a Sea-Bird SBE 32 compact carousel. The table below lists more detailed information about the various sensors.

Sensor Model Serial Number Calibration (UT) Comments
Pressure transducer Paroscientific Digiquartz 42K-105 76076 2004-01-21 -
Conductivity sensor SBE 4 2543 2004-01-14 -
Temperature sensor SBE 3 P4100 2004-01-21 -
Dissolved oxygen SBE 43 1491 2008-08-15 -
Transmissometer (660 nm) SeaTech T1000 T1021 1998-03-03 0.2 m path
Fluorometer Turner SCUFA II 262 - -
LISST 25A 120 2006-10-26 Range: 1.25 to 250 µm, Beam wavelength 670 nm
LI-COR (contains CEFAS in-house electronics) LI-192SB CEFAS #69 2009-04-17 -
Temperature Logger SBE 35 0041 2005-03-29 -

Change of sensors during cruise: None reported.

Sampling device

The rosette sampling system wasequipped with 5 l sampling bottles (Sea-Bird Improved PVC Sample Bottles based on design of Ocean Test Equipment Inc. model 110 bottle).

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.



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 PD02_10 CTD Processing

Sampling Strategy

A total of 24 CTD profiles were performed during the cruise throughout Liverpool Bay. Data were measured at 24 Hz and logged to a PC running SEASAVE, Sea-Bird's data acquisition software. Rosette bottles were fired throughout the water column on the upcast of the CTD profiles. Independent temperature data were recorded at the time of each bottle firing. Salinity samples were obtained from the near-bed bottles (plus two near-surface bottles), analysed at Bangor University (BU) and the results were sent to BODC. The Department of Earth and Ocean Sciences, University of Liverpool (DEOS) collected samples from the near-surface and near-bed rosette bottles for nutrient analysis with additional samples taken for the analysis of primary productivity. Water samples were taken from rosette bottles throughout the cruise for determination of alkalinity by the National Oceanography Centre, Southampton (NOCS). Samples from rosette bottles at 20 sites were filtered to determine suspended sediment load by the School of Ocean Sciences (SOS), Bangor University. Samples were taken from rosette bottles for analysis by CEFAS.

BODC Processing and screening

Data Processing

The raw CTD files were processed through the Sea-Bird SBE Data Processing software version 7.20c. Binary (.HEX) files were converted to engineering units and ASCII format (.CNV) using the DATCNV program.

Sea-Bird bottle files (.BTL), with information on pressure and other logged readings at the time of bottle firing, were also generated during the data conversion process.

WILDEDIT was not run on the data as no pressure spikes were present in the casts. FILTER was run on the pressure channel using the recommended time filter of 0.15 s.

Sea-Bird software program ALIGN CTD was run to advance conductivity by 0 s and oxygen by 3 s (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. LOOP EDIT was run to identify scans which were affected by ship heave. Salinity, density (Sigma-theta kg m-3) and oxygen concentration (ml l-1) were then calculated and added to the output files using the DERIVE program. BINAVERAGE was used to bin the data (both upcasts and downcasts) to 10 Hz and remove cycles flagged by LOOP EDIT. Finally, the first oxygen concentration channel and first salinity channel (both generated by DATCNV using data un-adjusted by ALIGN CTD and CELLTM) were dropped using STRIP.


The data were converted from ASCII format into BODC internal format (a subset of NetCDF) using BODC transfer function 357. The following table shows how the variables within the ASCII files were mapped to appropriate BODC parameter codes:

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
Pressure, Digiquartz dbar Pressure of water body on profiling pressure sensor PRESPR01 dbar -
Conductivity S m-1 Electrical conductivity of the water column by CTD CNDCST01 S m-1 -
Oxygen Voltage, SBE 43 Volts Instrument output (voltage) from SBE 43 sensor OXYVTLN1 Volts -
Oxygen, SBE 43 ml l-1 Dissolved oxygen concentration from SBE 43 sensor DOXYSU01 µmol l-1 Converted from ml l-1 to µmol 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 water column by CTD TEMPCU01 °C -
Voltage 2 Un-adjusted volts Voltage from CTD PAR Sensor LVLTLD01 Un-adjusted volts -
Voltage 3 Un-adjusted volts Beam transmissometer voltage TVLTCR01 Un-adjusted volts -
Voltage 4 Un-adjusted volts Voltage from CTD SCUFA II 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 by BODC using UNESCO Report 38 (1981) algorithm with parameters PSALCC01 and TEMPCC01
- - Sigma-theta SIGTPR01 kg m-3 Generated by BODC using the Fofonoff and Millard (1983) algorithm
- - PAR IRRDUV01 µE m-2 s-1 Generated by BODC from calibration of LVLTLD01
- - Beam Attenuation ATTNMR01 m-1 Generated by BODC from calibration of TVLTCR01
- - Temperature TEMPCC01 °C Generated by BODC from calibration of TEMPCU01
- - Salinity PSALCC01 - Generated by BODC from calibration of PSALCU01
- - Oxygen saturation OXYSSU01 % Generated by 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. Downcasts and upcasts were differentiated and the limits manually flagged.


Once quality control screening was complete, CTD downcasts for all casts (except CTD14 and CTD15 where the upcasts were used) were loaded into BODC's under the Oracle Relational Database Management System. The upcasts were used for CTD14 and CTD15 as the downcasts only had data recorded for pressures greater than 5.68 dbar and 4.64 dbar respectively. Finally, the casts were binned to 0.2 dbar.


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

Fofonoff, NP and Millard, RC (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



Salinity samples were taken throughout the water column then returned to SOS, where salinity was determined using a Portasal salinometer that was calibrated to standard seawater. The raw Sea-Bird data, configuration and bottle files were supplied to BODC for further processing.

21 independent salinity values (obtained from water samples from the CTD rosette) were compared to pressure and CTD salinity; 4 data points were identified as outliers and removed from the analysis. The mean offset between CTD salinity and independent salinity (Autosal salinity - CTD salinity) for this dataset was found, using linear regression, to be significantly related to independent salinity at a 95% confidence level. A calibration equation was derived from the linear regression as follows, based on 17 observations: calibrated CTD = Salinity *1.015125-0.52380. The RMS error for this dataset is 0.0062450. The mean offset is -0.01639 and the standard deviation is 0.00912.


109 independent temperature values were compared to pressure and CTD temperature; 22 data points were identified as outliers and were removed from the analysis. The temperature offset (SBE 35 temperature - CTD temperature) was found, using regression analysis, not to be significantly related to SBE 35 temperature at a 95% confidence level. The mean offset is -0.002515 °C and the standard deviation for this dataset is 0.003079 °C. This is at the lowest level of accuracy for both the SBE 35 and Sea-Bird 911plus CTD (+/- 0.001 °C). Therefore, there was no adjustment to the CTD temperature resulting from the application of manufacturer's coefficients during initial processing.


There were no casts where the CTD pressure was logging in air. No adjustments were made to the values resulting from application of manufacturer's coefficients during the initial 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 (4.32234 volts); Y1 is the current blocked path voltage (0.00 volts). For this cruise, M and B were calculated to be 21.5670 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])


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

LISST transmission and scattering

The data are currently supplied as voltages due to concerns about the observed variability in the clean water readings over time. With reliable clean water readings, 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, the coefficients supplied here are from clear water readings taken during the most recent manufacturer calibration (October 2006) as follows:

Ideally the manufacturer's clear water values should be substituted 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.

The clean water transmission and scattering voltages can be seen to both increase and decrease with time, showing inconsistency in either the instrument performance or the calibration dip method. Therefore, manufacturer's values have been quoted along with values measured by the instrument during previous cruises since the last manufacturer's calibration. Users are advised to use their own discretion in deciding which coefficients to apply.

Date (UT) Cruise VT0 VS0
2007-02-12 PD02_07 2.74 0.154
2007-04-15 PD06_07 2.722 0.167
2007-06-29 PD13_07 2.479 0.209
2007-07-25 PD16_07 2.430 0.211
2007-08-28 PD20_07 2.455 0.208
2007-11-20 PD27_07 2.707 0.158
2008-01-08 PD01_08 2.687 0.158
2008-02-12 PD04_08 N/A N/A
2008-03-10 PD07_08 2.66545 0.15873
2008-04-18 PD09_08 2.69353 0.15873
2008-05-12 PD14_08 2.62149 0.18315
2008-06-24 PD19_08 N/A N/A
2008-07-28 PD23_08 2.60562 0.17338
2008-12-09 PD37_08 2.59341 0.15995
2009-02-01 PD02_09A 2.59829 0.15751
2009-03-31 PD12_09 2.52381 0.17216
2009-05-11 PD18_09 2.55433 0.18315
2009-06-02 PD22_09 Not recorded Not recorded
2009-08-02 PD33_09 2.76923 0.17216
2009-09-14 PD38_09 2.73626 0.16728
2009-12-01 PD47_09 2.82796 0.16239
2010-01-25 PD02_10 2.74359 0.16484


During instrument deployment, no effort was made to avoid data collection possibly being affected by ship shadowing. The LI-COR LI-192SB sensor number 69 was calibrated from raw voltages using the CEFAS supplied equation:

PAR (µE m-2 s-1) = 0.151282*exp(measured voltage * 3.432)

Project Information

Proudman Oceanographic Laboratory Coastal Observatory

The Coastal Observatory was established by Proudman Oceanographic Laboratory as a coastal zone real time observing and monitoring system. The main objective is to understand a coastal sea's response both to natural forcing and to the consequences of human activity. Near real-time measurements will be integrated with coupled models into a pre-operational coastal prediction system whose results will be displayed on the World Wide Web.

The Observatory is expected to grow and evolve as resources and technology allow, all the while building up long time series. A site selection pilot study was carried out in September 2001 and the Observatory became operational in August 2002.

The site is located in Liverpool Bay and is subject to typical coastal sea processes, with strong tides, occasional large storm surges and waves, freshwater input, stable and unstable stratification, high suspended sediment concentration and biogeochemical interaction. Measurements and monitoring will focus on the impacts of storms, variations in river discharge (especially the Mersey), seasonality and blooms in Liverpool Bay.

A variety of methods will be used to obtain measurements, including:

  1. Moored instruments for in situ time series of currents, temperature and salinity profiles, and surface waves and meteorology. It is hoped that turbidity and chlorophyll measurements will be made at another site as the Observatory progresses;
  2. The Cefas Smartbuoy for surface properties such as nutrients and chlorophyll, starting late 2002;
  3. R.V. Prince Madog to carry out spatial surveys and service moorings;
  4. Instrumented ferries for near surface temperature, salinity, turbidity, chlorophyll and nutrients. The first route will be Liverpool to Douglas, Isle of Man, starting late 2002;
  5. Drifters for surface currents and properties such as temperature and salinity, starting in 2004;
  6. Tide gauges, with sensors for meteorology, waves, temperature and salinity, where appropriate;
  7. Meteorological data from Bidston Observatory and Hilbre Island, HF radar and tide gauge sites;
  8. Shore-based HF radar measuring waves and surface currents out to a range of 50 km, starting in 2003;
  9. Satellite data, with infrared for sea surface temperature and visible for chlorophyll and suspended sediment.

The partners currently involved with the project are listed below:

A summary of Coastal Observatory cruises to date on R.V. Prince Madog is given in the table below:

Year No. of cruises Work summary
2001 1 Site selection and pilot study. 95 CTD casts.
2002 4 POL moorings deployed and serviced
Cefas Waverider and SmartBuoy deployed and serviced
103 CTD casts
2003 10 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
341 CTD/LISST casts
2004 9 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
347 CTD/LISST casts
2005 9 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
268 CTD/LISST casts
2006 11 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
508 CTD/LISST casts
2007 9 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
471 CTD/LISST casts
2008 9 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
260 CTD/LISST casts
2009 7 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
213 CTD/LISST casts
2010 8 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
268 CTD/LISST casts
2011 6 POL moorings serviced
Cefas Waverider and SmartBuoy serviced
307 CTD/LISST casts to date, ongoing

Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.

Oceans 2025 Theme 10, Sustained Observation Activity 11: Liverpool Bay and Irish Sea Coastal Observatory

Sustained, systematic observations of the ocean and continental shelf seas at appropriate time and space scales allied to numerical models are key to understanding and prediction. In shelf seas these observations address issues as fundamental as 'what is the capacity of shelf seas to absorb change?' encompassing the impacts of climate change, biological productivity and diversity, sustainable management, pollution and public health, safety at sea and extreme events. Advancing understanding of coastal processes to use and manage these resources better is challenging; important controlling processes occur over a broad range of spatial and temporal scales which cannot be simultaneously studied solely with satellite or ship-based platforms.

Considerable effort has been spent by the Proudman Oceangraphic Laboratory (POL) in the years 2001 - 2006 in setting up an integrated observational and now-cast modelling system in Liverpool Bay (see Figure), with the recent POL review stating the observatory was seen as a leader in its field and a unique 'selling' point of the laboratory. Cost benefit analysis (IACMST, 2004) shows that benefits really start to accrue after 10 years. In 2007 - 2012 exploitation of (i) the time series being acquired, (ii) the model-data synthesis and (iii) the increasingly available quantities of real-time data (e.g. river flows) can be carried out through Sustained Observation Activity (SO) 11, to provide an integrated assessment and short term forecasts of the coastal ocean state.

BODC image

Overall Aims and Purpose of SO 11

Measurement and Modelling Activities

More detailed information on this Work Package is available at pages 32 - 35 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10



IACMST., 2004. The Economics of Sustained Marine Measurements. IACMST Information Document, N0.11, Southampton: IACMST, 96 pp

Data Activity or Cruise Information


Cruise Name PD02/10
Departure Date 2010-01-26
Arrival Date 2010-01-27
Principal Scientist(s)Matthew R Palmer (Proudman Oceanographic Laboratory)
Ship RV Prince Madog

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NameCoastal Observatory Site 30
CategoryOffshore area
Latitude53° 42.22' N
Longitude3° 55.16' W
Water depth below MSL40.5 m

Liverpool Bay Coastal Observatory Site 30

This station is one of 34 stations regularly visited by the Proudman Oceanographic Laboratory (POL) as part of the Liverpool Bay Coastal Observatory. During each site visit, CTD profiles are taken. The station lies within a box of mean water depth 40.5 m with the following co-ordinates:

Box Corner Latitude Longitude
North-west corner 53.71035° -3.93378°
South-east corner 53.69701° -3.90496°

The position of this station relative to the other POL Coastal Observatory sites can be seen from the figure below.

BODC image

CTD Sampling History

Year Number of Visits Total Casts per year
2011 4 4
2010 6 6
2009 5 5
2008 3 3
2007 6 6
2006 7 7
2005 4 4
2004 7 7
2003 7 7
2002 1 1

The CTD instrument package for these cruises was a Sea-Bird 911plus, with beam transmissometer, fluorometer, LICOR PAR sensor, LISST-25, and oxygen sensor.

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
Q value below limit of quantification

Appendix 1: Coastal Observatory Site 30

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
1013038CTD or STD cast2006-11-02 01:19:0053.70917 N, 3.927 WRV Prince Madog PD35/06
937839CTD or STD cast2007-04-20 06:29:0053.70317 N, 3.926 WRV Prince Madog PD06/07
942356CTD or STD cast2007-05-17 17:00:0053.70267 N, 3.92967 WRV Prince Madog PD09/07
942946CTD or STD cast2007-06-21 03:36:0053.701 N, 3.9255 WRV Prince Madog PD13/07
943532CTD or STD cast2007-07-28 01:52:0053.69933 N, 3.927 WRV Prince Madog PD16/07
943913CTD or STD cast2007-08-30 15:05:0053.70017 N, 3.92983 WRV Prince Madog PD20/07
945852CTD or STD cast2007-10-04 17:56:0053.697 N, 3.91983 WRV Prince Madog PD23/07
948340CTD or STD cast2008-05-16 00:08:0053.70083 N, 3.93383 WRV Prince Madog PD14/08
949619CTD or STD cast2008-07-31 16:18:0053.70317 N, 3.92383 WRV Prince Madog PD23/08
950006CTD or STD cast2008-12-11 01:43:0053.69833 N, 3.929 WRV Prince Madog PD37/08
950368CTD or STD cast2009-02-06 01:27:0053.69883 N, 3.92683 WRV Prince Madog PD02/09B
951323CTD or STD cast2009-04-01 17:02:0053.70217 N, 3.93 WRV Prince Madog PD12/09
953599CTD or STD cast2009-05-12 16:33:0053.70217 N, 3.92933 WRV Prince Madog PD18/09
1023647CTD or STD cast2009-08-04 01:20:0053.70117 N, 3.9225 WRV Prince Madog PD33/09
1024190CTD or STD cast2009-09-15 18:21:0053.6985 N, 3.916 WRV Prince Madog PD38/09
1090475CTD or STD cast2010-06-09 21:20:0053.69717 N, 3.92717 WRV Prince Madog PD17/10
1091012CTD or STD cast2010-07-08 09:57:0053.69833 N, 3.922 WRV Prince Madog PD21/10
1112141CTD or STD cast2010-08-11 17:45:0053.7015 N, 3.923 WRV Prince Madog PD29/10
1114006CTD or STD cast2010-09-28 16:45:0053.7 N, 3.92917 WRV Prince Madog PD36/10
1148906CTD or STD cast2011-01-12 17:36:0053.70183 N, 3.92783 WRV Prince Madog PD01/11
1149774CTD or STD cast2011-03-16 20:52:0053.70017 N, 3.92067 WRV Prince Madog PD07/11
1117606CTD or STD cast2011-04-20 01:56:0053.69967 N, 3.928 WRV Prince Madog PD11/11