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Metadata Report for BODC Series Reference Number 819205

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 research vessel
Originating Country United Kingdom
Originator Prof John Simpson
Originating Organization University of Wales, Bangor School of Ocean Sciences (now Bangor University School of Ocean Sciences)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) North Sea Project 1987-1992
NSP Frontal Process Study

Data Identifiers

Originator's Identifier 2363
BODC Series Reference 819205

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1989-07-09 22:57
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 53.89733 N ( 53° 53.8' N )
Longitude 0.41750 E ( 0° 25.0' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 1.49 m
Maximum Sensor or Sampling Depth 45.09 m
Minimum Sensor or Sampling Height 0.9 m
Maximum Sensor or Sampling Height 44.51 m
Sea Floor Depth 46.0 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

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

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 56 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 -1.6 db, was added to each pressure value.

Two digital reversing thermometers were fired at the bottom of each cast. The mean difference, determined for all casts on the cruise, between the averaged calibrated readings and the CTD temperature, 0.006 °C, was added to the CTD temperatures.

A sample was taken from the bottom bottle of each cast and salinity was determined using a Guildline Autosal. The mean difference, determined for all casts on the cruise, between the bottle values and the CTD salinity, 0.071 PSU, was added to the CTD salinities.

No extracted chlorophyll values were determined on this cruise. Consequently, no chlorophyll calibration was possible. Note that for part or all of the cruise, it is possible that the fluorometer was fitted with filters for detecting rhodamine tracer and hence the resulting voltages were not be used for estimating chlorophyll.

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


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 Frontal Process Study

The nearshore, mixing and circulation fronts studies all concerned the front extending from the region of Flamborough Head offshore between summer stratified water to the north and well mixed water to the south. The associated local circulation and distinctive dispersion, notably by eddies exchanging material across the front, are important to North Sea transports of all water-borne constituents. In collaboration with MAFF, moorings were laid and CTD, ADCP and SeaSoar surveys carried out to define the dynamical fields for model testing and interpretation. Near shore HF radar gave synoptic coverage of large scale and eddy contributions to transport. Further offshore drogue tracks and the spreading of released Rhodamine B was used both to assess circulation and horizontal and vertical mixing.

Moorings were deployed at five stratified sites (FA, FB, FC, DA and DB) to study the circulation in the frontal area.

The deployment history is summarised below:

Site Position Rig Deployment
FA 53° 59.87'N, 000° 09.43'E 56381 09 July 1989  
FB 54° 03.45'N, 000° 17.42'E 56382 09 July 1989  
FC No data returned
DA 54° 53.98'N, 001° 11.70'E 56386 11 July 1989 Transmissometer mooring lost
DB 54° 55.05'N, 001° 04.06'E 56388 11 July 1989  

Data Activity or Cruise Information


Cruise Name CH56
Departure Date 1989-07-08
Arrival Date 1989-07-22
Principal Scientist(s)Ian D James (Proudman Oceanographic Laboratory)
Ship RRS Challenger

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NameNSP CTD Site DO
CategoryOffshore location
Latitude53° 54.56' N
Longitude0° 23.56' E
Water depth below MSL

North Sea Project CTD Site DO

Site DO was one of 123 North Sea Project CTD fixed stations.

Casts were performed by 17 cruises between 15/08/1988 and 01/10/1990, the measurements collected lie within a box bounded by co-ordinates 53.8974°N, 0.36787°E at the southwest corner and 53.92134°N, 0.41752°E at the northeast corner.

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 CTD Site DO

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
770030CTD or STD cast1988-08-15 05:28:0053.90317 N, 0.36783 ERRS Challenger CH33
784062CTD or STD cast1988-09-14 08:06:0053.91667 N, 0.39683 ERRS Challenger CH35
784885CTD or STD cast1988-10-12 07:58:0053.91633 N, 0.40683 ERRS Challenger CH37
822329CTD or STD cast1988-11-11 22:01:0053.919 N, 0.39983 ERRS Challenger CH39
785201CTD or STD cast1988-12-07 05:33:0053.91533 N, 0.40583 ERRS Challenger CH41
785919CTD or STD cast1988-12-31 18:16:0053.91617 N, 0.39783 ERRS Challenger CH43
791962CTD or STD cast1989-02-07 16:56:0053.91283 N, 0.4035 ERRS Challenger CH45
793409CTD or STD cast1989-03-09 19:31:0053.92133 N, 0.40333 ERRS Challenger CH47
1858134Water sample data1989-03-09 19:34:0053.92134 N, 0.40325 ERRS Challenger CH47
794566CTD or STD cast1989-04-09 11:31:0053.92 N, 0.40033 ERRS Challenger CH49
1859242Water sample data1989-04-09 11:34:0053.92004 N, 0.40032 ERRS Challenger CH49
795637CTD or STD cast1989-05-06 19:49:0053.9145 N, 0.4005 ERRS Challenger CH51
1861479Water sample data1989-05-06 19:56:0053.91444 N, 0.40057 ERRS Challenger CH51
2082737Water sample data1989-05-06 19:56:0953.91444 N, 0.40057 ERRS Challenger CH51
2096493Water sample data1989-05-06 19:56:0953.91444 N, 0.40057 ERRS Challenger CH51
2097515Water sample data1989-05-06 19:56:0953.91444 N, 0.40057 ERRS Challenger CH51
797122CTD or STD cast1989-06-05 08:58:0053.91867 N, 0.3995 ERRS Challenger CH53
1864152Water sample data1989-06-05 09:03:0053.91862 N, 0.39946 ERRS Challenger CH53
798518CTD or STD cast1989-07-05 13:32:0053.9185 N, 0.39767 ERRS Challenger CH55
1657442Water sample data1989-07-05 13:36:0053.91855 N, 0.39774 ERRS Challenger CH55
1866724Water sample data1989-07-05 13:36:0053.91855 N, 0.39774 ERRS Challenger CH55
799767CTD or STD cast1989-08-05 09:40:0053.91517 N, 0.389 ERRS Challenger CH57
1246581Water sample data1989-08-05 09:43:0053.91521 N, 0.38897 ERRS Challenger CH57
1710036Water sample data1989-08-05 09:43:0053.91521 N, 0.38897 ERRS Challenger CH57
1865419Water sample data1989-08-05 09:43:0053.91521 N, 0.38897 ERRS Challenger CH57
802316CTD or STD cast1989-09-02 13:05:0053.91917 N, 0.3955 ERRS Challenger CH59
1857002Water sample data1989-09-02 13:09:0053.91922 N, 0.39546 ERRS Challenger CH59
800973CTD or STD cast1989-10-02 00:25:0053.91533 N, 0.39983 ERRS Challenger CH61
1855738Water sample data1989-10-02 00:29:0053.91533 N, 0.39989 ERRS Challenger CH61
2086984Water sample data1989-10-02 00:29:1453.91533 N, 0.39989 ERRS Challenger CH61
2088211Water sample data1989-10-02 00:29:1453.91533 N, 0.39989 ERRS Challenger CH61
805326CTD or STD cast1990-10-01 12:21:0053.91517 N, 0.398 ERRS Challenger CH72A