Search the data

Metadata Report for BODC Series Reference Number 813688

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
SeaTech transmissometer  transmissometers
Chelsea Technologies Group Aquatracka fluorometer  fluorometers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Prof Mike Collins
Originating Organization University of Southampton Department of Oceanography (now University of Southampton School of Ocean and Earth Science)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) North Sea Project 1987-1992
NSP Sandwaves/Sandbanks Process Study

Data Identifiers

Originator's Identifier 972
BODC Series Reference 813688

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1988-11-21 12:57
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 53.26333 N ( 53° 15.8' N )
Longitude 2.19850 E ( 2° 11.9' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 2.48 m
Maximum Sensor or Sampling Depth 30.23 m
Minimum Sensor or Sampling Height 6.77 m
Maximum Sensor or Sampling Height 34.52 m
Sea Floor Depth 37.0 m
Sea Floor Depth Source PEVENT
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
ATTNZR011per metreAttenuation (red light wavelength) per unit length of the water body by transmissometer
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALST011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTPR011Kilograms per cubic metreSigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPST011Degrees CelsiusTemperature of the water body by CTD or STD

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data Access Policy

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

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.


These specification apply to the MK3C version.

Pressure Temperature Conductivity

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm-1

0.0015% FS

0.03% FS < 1 msec


0.003°C < 30 msec

0.0001 S cm-1

0.0003 S cm-1 < 30 msec

Further details can be found in the specification sheet.

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

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.

RRS Challenger 40 CTD Data Documentation


The CTD unit was a Neil Brown Mk. 3 incorporating a pressure sensor, conductivity cell, platinum resistance thermometer, and a Beckmann dissolved oxygen sensor. This was mounted vertically in the centre of a protective cage.

Attached to bars of the frame were an Aquatracka logarithmic response fluorometer and a Seatech red light (661 nm) transmissometer with a 25 cm path length.

To the side of the frame was a rosette sampler which could be fitted with up to 12, 1.7 litre Niskin bottles. The base of the bottles were in line with the pressure head. One bottle was fitted with a holder for twin reversing thermometers mounted marginally above the CTD temperature sensor.

Operational procedure and data logging

On each cast the CTD was lowered to a depth of approximately 5 metres and held until the instrument stabilised. It was then raised to the surface and lowered continuously at 0.5 to 1 m/s to as close as possible to the sea floor. The upcast was done in stages between the bottle firing depths.

Data were logged by the Research Vessel Services ABC data logging system. The deck unit outputs were sampled at 32 Hz by a microprocessor interface (the Level A) which passed time stamped averaged cycles at 1 Hz to a Sun workstation (the Level C) via a buffering system (the Level B).

Data processing

The raw data comprised ADC counts. These were converted into engineering units (Volts for fluorometer and transmissometer: ml/l for oxygen: mmho/cm for conductivity: °C for temperature) by the application of laboratory determined calibrations and salinity was computed using the algorithm in Fofonoff and Millard (1983). The data were submitted to BODC in this form.

Within BODC the data were reformatted on an IBM main-frame. At this stage transmissometer air readings recorded during the cruise were used to correct the transmissometer voltage to the manufacturer's specified voltage by ratio. The voltages were then converted to percentage transmittance (multiplied by 20.0) and dissolved oxygen converted to µM (multiplied by 44.66).

Next the data were loaded onto a Silicon Graphics workstation. A sophisticated interactive screening program was used to delimit the downcast, mark the depth range of water bottle firings and flag any spikes on all of the data channels.

The data were returned to the IBM and the downcasts loaded into a database under the Oracle relational database management system. At this stage percentage transmittance was converted to attenuance to eliminate the influence of instrument path length using the equation:

Attenuance = -4.0 * loge (% trans/100)

Calibration sample data were merged into the database and files of sample value against CTD reading at the bottle depth were prepared for the Principal Investigators to determine the calibrations. Due allowance was made for rig geometry. Note that CTD downcast values were generally used although the bottles were fired on the upcast. The validity of an assumed static water column for the duration of the cast was checked on the graphics workstation and upcast values substituted if necessary.

Sigma-T values were calculated using the algorithm presented in Fofonoff and Millard (1983).


For each cast the mean pressure reading logged whilst the instrument was in air was determined. The average of these, determined as -0.37 db, was added to each pressure value.

Two digital reversing thermometers were fired at the bottom of each cast. The mean of the two temperatures was regressed against CTD temperature to give the calibration equation:

Calibrated temp (°C) = Raw temp * 0.99814 + 0.0131

A sample was taken from the bottom bottle of each cast and salinity was determined using a Guildline Autosal. The bottle salinities were regressed against CTD salinity to give the calibration equation:

Calibrated salinity (PSU) = Raw salinity * 0.9749 + 0.87138

No extracted chlorophyll values were determined on this cruise. Consequently, no chlorophyll calibration was possible.

No dissolved oxygen calibration samples were taken on this cruise and therefore no calibration was possible. All CTD oxygen values have been flagged as suspect to reflect this.

No suspended matter determinations were made on this cruise. Consequently, there are no transmissometer channels other than attenuance.


No chlorophyll data are available, only uncalibrated voltages.

No dissolved oxygen data are available.

No suspended matter data are available.


Fofonoff, N.P and Millard, R.C. Jr. (1983). Algorithms for the computation of fundamental properties of sea water.

Project Information

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

  • Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
  • Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
  • Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Table 1: Details of NSP Survey Cruises on RRS Challenger
Cruise No. Date
CH28 29/04/88 - 15/05/88
CH33 04/08/88 - 16/08/88
CH35 03/09/88 - 15/09/88
CH37 02/10/88 - 14/10/88
CH39 01/11/88 - 13/11/88
CH41 01/12/88 - 13/12/88
CH43 30/12/88 - 12/01/89
CH45 28/01/89 - 10/02/89
CH47 27/02/89 - 12/03/89
CH49 29/03/89 - 10/04/89
CH51 27/04/89 - 09/05/89
CH53 26/05/89 - 07/06/89
CH55 24/06/89 - 07/07/89
CH57 24/07/89 - 06/08/89
CH59 23/08/89 - 04/09/89
CH61 21/09/89 - 03/10/89

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

Table 2: Details of NSP Process cruises on RRS Challenger
Cruise No. Date Process
CH34 18/08/88 - 01/09/88 Fronts - nearshore
CH36 16/09/88 - 30/09/88 Fronts - mixing
CH56 08/07/89 - 22/07/89 Fronts - circulation
CH58 07/08/89 - 21/08/89 Fronts - mixing
CH38 24/10/88 - 31/10/88 Sandwaves
CH40 15/11/88 - 29/11/88 Sandbanks
CH42 15/12/88 - 29/12/88 Plumes/Sandbanks
CH46 12/02/89 - 26/02/89 Plumes/Sandwaves
CH44 13/01/89 - 27/01/89 Resuspension
CH52 11/05/89 - 24/05/89 Resuspension
CH60 06/09/89 - 19/09/89 Resuspension
CH48 13/03/89 - 27/03/89 Air/sea exchanges
CH62 05/10/89 - 19/10/89 Air/sea exchanges
CH50 12/04/89 - 25/04/89 Blooms/chemistry
CH54 09/06/89 - 22/06/89 Production

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

Table 3: Details of NSP `Follow up' cruises on RRS Challenger
Cruise No. Date Process
CH62A 23/10/89 - 03/11/89 Blooms
CH64 03/04/90 - 03/05/90 Blooms
CH65 06/05/90 - 17/05/90 Humber plume
CH66A 20/05/90 - 31/05/90 Survey
CH66B 03/06/90 - 18/06/90 Contaminants through Dover Strait
CH69 26/07/90 - 07/08/90 Resuspension/Plumes
CH72A 20/09/90 - 02/10/90 Survey
CH72B 04/10/90 - 06/10/90 Sandwaves/STABLE
CH72C 06/10/90 - 19/10/90 Rhine plume

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

North Sea Project Sandwaves and Sandbanks Process Study

Sandwave fields cover at least 15000 km2 of the Southern Bight of the North Sea. Drag coefficients based on measured pressure gradients were recorded and sea bed photography used to test bedload prediction formulae. The sand covering much of the southern North Sea is mobile forming banks that are interleaved with mud. Current meter moorings placed either side of a bank were used to estimate its associated circulation and contribution to dispersion. A 3 dimensional model using wave-current interaction enhancing bed stress is being applied to fine grid (~100m) bathymetry and is being tested using detailed measurements of near-bed currents and turbulence obtained from the STABLE (Sediment Transport And Boundary Layer Equipment) rig.

Data Activity or Cruise Information


Cruise Name CH40
Departure Date 1988-11-15
Arrival Date 1988-11-29
Principal Scientist(s)Michael B Collins (University of Southampton Department of Oceanography)
Ship RRS Challenger

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NameNSP Sandbanks Experiment
CategoryOffshore location
Latitude53° 1.80' N
Longitude2° 11.00' E
Water depth below MSL34.0 m

NSP Sandbank Process Studies Moorings

The sandbank process studies carried out investigations into the influence of sandbanks on regional water flow patterns, including water and sand movement, in the Norfolk Banks region of the southern North Sea. It complimented a similar investigation into drag and sediment movement over sandwaves off the Dutch coast.

Moorings deployed included rigs with pressure sensors, a variety of current meters and STABLE (Sediment Transport and Boundary Layer Equipment).

The rigs deployed during this experiment lie within a box bounded by co-ordinates 53° 10.66' N, 002°4.07' E at the southwest corner and 53° 22.09' N, 002° 17.89' E at the northeast corner.

The deployment history for this station is summarised below:

Rig / Instrument Identification Meter Type Start Date Data Return(Days) Comments
CH40PS1/T284 WR 17Nov88 85.0  
CH40PS2/TG05 WR 17Nov88 29.0  
CH40B/AS7517 CM 17Nov88 9.0  
CH40B/AS7946 CM 17Nov88 9.0  
CH40B/UCM23 CM 17Nov88 8.0  
CH40E/AS7947 CM 17Nov88 10.0  
CH40F/AS2109 CM 17Nov88 10.0  
CH40G/AA3277 CM 16Nov88 10.0  
CH40G/UCM20 CM 16Nov88 10.0  
CH40H/AA3559 CM 16Nov88 10.0  
CH40H/UCM22 CM 16Nov88 10.0  
CH40/STABLE1 SM 19Nov88 3.0 One minute mean data for current speed and pressure only.


  • WR = Water Level Recorder
  • CM = Current Meter

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: NSP Sandbanks Experiment

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
592508Offshore sea floor pressure series1988-11-17 08:37:3053.2475 N, 2.2982 ENot applicable
592489Offshore sea floor pressure series1988-11-17 19:37:3053.3682 N, 2.0678 ENot applicable
611514Currents -subsurface Eulerian1988-11-19 13:11:0053.2408 N, 2.2447 ENot applicable
813191CTD or STD cast1988-11-19 20:18:0053.22317 N, 2.241 ERRS Challenger CH40
813209CTD or STD cast1988-11-20 10:37:0053.30583 N, 2.13117 ERRS Challenger CH40
813210CTD or STD cast1988-11-20 11:30:0053.30867 N, 2.14333 ERRS Challenger CH40
813222CTD or STD cast1988-11-20 12:03:0053.31183 N, 2.1495 ERRS Challenger CH40
813234CTD or STD cast1988-11-20 12:48:0053.31367 N, 2.16133 ERRS Challenger CH40
813246CTD or STD cast1988-11-20 13:54:0053.31483 N, 2.16133 ERRS Challenger CH40
813258CTD or STD cast1988-11-20 14:37:0053.327 N, 2.181 ERRS Challenger CH40
813271CTD or STD cast1988-11-20 15:12:0053.33483 N, 2.19233 ERRS Challenger CH40
813283CTD or STD cast1988-11-20 16:12:0053.34433 N, 2.21217 ERRS Challenger CH40
813295CTD or STD cast1988-11-20 16:58:0053.35017 N, 2.2245 ERRS Challenger CH40
813302CTD or STD cast1988-11-20 17:53:0053.265 N, 2.23617 ERRS Challenger CH40
813314CTD or STD cast1988-11-20 18:40:0053.27483 N, 2.254 ERRS Challenger CH40
813326CTD or STD cast1988-11-20 19:20:0053.293 N, 2.2645 ERRS Challenger CH40
813664CTD or STD cast1988-11-20 19:56:0053.30383 N, 2.27817 ERRS Challenger CH40
813338CTD or STD cast1988-11-20 21:09:0053.227 N, 2.22917 ERRS Challenger CH40
813351CTD or STD cast1988-11-20 21:34:0053.22883 N, 2.23133 ERRS Challenger CH40
813363CTD or STD cast1988-11-20 22:11:0053.22483 N, 2.23417 ERRS Challenger CH40
813375CTD or STD cast1988-11-20 22:50:0053.22183 N, 2.233 ERRS Challenger CH40
813387CTD or STD cast1988-11-20 23:36:0053.227 N, 2.2375 ERRS Challenger CH40
813399CTD or STD cast1988-11-21 00:11:0053.22583 N, 2.23133 ERRS Challenger CH40
813406CTD or STD cast1988-11-21 00:34:0053.231 N, 2.22717 ERRS Challenger CH40
813418CTD or STD cast1988-11-21 01:04:0053.22067 N, 2.244 ERRS Challenger CH40
813431CTD or STD cast1988-11-21 01:34:0053.22633 N, 2.23717 ERRS Challenger CH40
813443CTD or STD cast1988-11-21 02:03:0053.22633 N, 2.243 ERRS Challenger CH40
813455CTD or STD cast1988-11-21 02:34:0053.22267 N, 2.24467 ERRS Challenger CH40
813467CTD or STD cast1988-11-21 03:04:0053.227 N, 2.2405 ERRS Challenger CH40
813479CTD or STD cast1988-11-21 03:33:0053.22317 N, 2.24433 ERRS Challenger CH40
813480CTD or STD cast1988-11-21 04:04:0053.22383 N, 2.245 ERRS Challenger CH40
813492CTD or STD cast1988-11-21 04:34:0053.2265 N, 2.243 ERRS Challenger CH40
813511CTD or STD cast1988-11-21 05:06:0053.22433 N, 2.23817 ERRS Challenger CH40
813523CTD or STD cast1988-11-21 05:35:0053.22383 N, 2.24533 ERRS Challenger CH40
813535CTD or STD cast1988-11-21 06:04:0053.223 N, 2.244 ERRS Challenger CH40
813547CTD or STD cast1988-11-21 06:37:0053.228 N, 2.23683 ERRS Challenger CH40
813559CTD or STD cast1988-11-21 07:03:0053.22267 N, 2.24283 ERRS Challenger CH40
813560CTD or STD cast1988-11-21 07:34:0053.22317 N, 2.24667 ERRS Challenger CH40
813676CTD or STD cast1988-11-21 07:45:0053.22083 N, 2.2475 ERRS Challenger CH40
813572CTD or STD cast1988-11-21 08:07:0053.22383 N, 2.239 ERRS Challenger CH40
813584CTD or STD cast1988-11-21 08:38:0053.22817 N, 2.23233 ERRS Challenger CH40
813596CTD or STD cast1988-11-21 09:09:0053.2285 N, 2.23133 ERRS Challenger CH40
813603CTD or STD cast1988-11-21 10:25:0053.23583 N, 2.2265 ERRS Challenger CH40
813615CTD or STD cast1988-11-21 11:51:0053.22533 N, 2.232 ERRS Challenger CH40