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Metadata Report for BODC Series Reference Number 953483

Metadata Summary

Data Description

Data Category Surface temp/sal
Instrument Type
SeaTech transmissometer  transmissometers
Chelsea Technologies Group Aquatracka fluorometer  fluorometers
Technicon AutoAnalyzer II colorimetric autoanalyser  colorimeters; autoanalysers
Grundy Environmental 6620 thermosalinograph  thermosalinographs; water temperature sensor; salinity sensor
Decca main chain navigation receiver  Decca Navigator System main chain receivers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Prof Nick Owens
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) North Sea Project 1987-1992

Data Identifiers

Originator's Identifier CH64_SURF
BODC Series Reference 953483

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1990-04-04 08:20
End Time (yyyy-mm-dd hh:mm) 1990-05-02 15:22
Nominal Cycle Interval 30.0 seconds

Spatial Co-ordinates

Southernmost Latitude 51.21783 N ( 51° 13.1' N )
Northernmost Latitude 60.30517 N ( 60° 18.3' N )
Westernmost Longitude 3.41917 W ( 3° 25.2' W )
Easternmost Longitude 8.34533 E ( 8° 20.7' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 2.0 m
Maximum Sensor or Sampling Depth 2.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor or Sampling Depth Datum Approximate - Depth is only approximate
Sea Floor Depth Datum -


BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ALATDE011DegreesLatitude north by Decca navigation
ALATTCNP1DegreesLatitude north by unspecified navigation system and recomputation to water location at fixed time using POL NSP model
ALONDE011DegreesLongitude east by Decca navigation
ALONTCNP1DegreesLongitude east by unspecified navigation system and recomputation to water location at fixed time using POL NSP model
AMONAAD21Micromoles per litreConcentration of ammonium {NH4+ CAS 14798-03-9} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
ATTNMR011per metreAttenuation (red light wavelength) per unit length of the water body by 20 or 25cm path length transmissometer
CPHLUW011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by Aquatracka fluorometer immersed in non-toxic supply and calibration against sample data
NTRIAAD21Micromoles per litreConcentration of nitrite {NO2- CAS 14797-65-0} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
NTRZAAD21Micromoles per litreConcentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
PHOSAAD21Micromoles per litreConcentration of phosphate {PO43- CAS 14265-44-2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
PSALSG011DimensionlessPractical salinity of the water body by thermosalinograph and computation using UNESCO 1983 algorithm and calibration against independent measurements
SLCAAAD21Micromoles per litreConcentration of silicate {SiO44- CAS 17181-37-2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
TEMPSG011Degrees CelsiusTemperature of the water body by thermosalinograph and verification against independent measurements
TSEDTR011Milligrams per litreConcentration of suspended particulate material {SPM} per unit volume of the water body [particulate >unknown phase] by in-situ optical attenuance measurement and calibration against sample data
UREAAAD21Micromoles per litreConcentration of urea {CAS 57-13-6} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis

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

CH64 Sea surface hydrographic data quality report

Dissolved Oxygen

No dissolved oxygen data.

Temperature and Salinity

The 6620 thermosalinograph uses an internal analogue computation and outputs salinity directly. The salinity algorithm used is unknown (no manual can be found for the instrument) but as the instrument dates from 1979 it is almost certain to differ from the one used for the earlier North Sea Project cruises. The consequence of this is a systematic salinity error which increases in magnitude as salinity deviates from 35.0. This will be partially, though not completely, corrected by the intercalibration with the CTD. The 6620 has no autoranging facility, and ranges have to be manually set by switches on the thermosalinograph unit. If the data moved out of range, a constant, incorrect value was logged. Significant amounts of data were lost in this manner.

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

Technicon AutoAnalyzer II (AAII)

The AAII is a segmented flow analyzer used for automated colorimetric analysis. The apparatus uses 2 mm diameter glass tubing and pumps reagents at flow rates of 2 to 3 ml s-1, producing results at a typical rate of 30 to 60 samples per hour. The system comprises an autosampler, peristaltic pump, chemistry manifold a detector and a data acquisition software.

This instrument was replaced by the AA3 in 1997 which was upgraded to the AA3 HR systems in 2006.


Frequency 420 kHz
Beam width 1.8° at -3 dB
Pulse lenght 0.1 m
Acoustic range precision ± 2.5 cm
Sampling rate 1 Hz
Tilt accuracy ± 0.5°
Tilt resolution ± 0.01°

Diameter of ensonified area
(dependent on acoustic range)

0.9 m for 30 m range

3.1 m for 100 m range

6.3 m for 200 m range

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.

Decca Navigator System

The Decca Navigator System (DNS) was a hyperbolic radio navigation system that operated by measuring the phase differences between continuous signals from master and slave stations. The differences were then related to hyperbolic lines printed on a chart (also known as lines of lattice). By plotting the readings from two pairs of hyperbolas at any particular instant, the user was able to plot their position instantly. The system operated from WWII until the UK transmitters were switched off at the end of March 2000.

The DNS consisted of groups of at least three shore based transmitter stations (or chains) which comprised one Master and two or three slave stations, usually located 80 to 110 km from the master station and positioned about 120° apart. The accuracy of this system depended on the distance to the baseline, time of day and seasonal effects.

The table below presents the general specifications for this system.


Frequency 70 - 130 kHz

50 m (daytime)

200 m (at night)

Maximum Range

300 - 400 nm (daytime)

240 nm (at night)

Further details can be found here.

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.

CH64 Sea surface hydrography instrument details

Underway hydrography was recorded by a suite of instruments in the ship's flow-through system. Instrument details are given in the table below.

Instrument type Make and model
Decca unspecified
Thermosalinograph Grundy Environmental 6620
Fluorometer Chelsea Instruments Aquatracka
Transmissometer SeaTech 661nm, 25cm path

CH64 Sea surface Hydrography Series Processing Notes


Discrete water samples were drawn off the non-toxic supply for determinations of nitrate plus nitrite using a ChemLab AA-II segmented continuous flow autoanalyser. The chemistry used was similar to that described in Grasshof et al (1983). Peak heights were interpreted using a ChemLab PHA interface and software running on an IBM PS2/50. Calibration was achieved by the measurement of a set of standards run in duplicate at the beginning of the run to which a third order polynomial, forced to pass through the origin, was fitted. The samples analysed were unfiltered.

The chemistries used were:

Nitrate: Reduced to nitrite by a Cu/Cd coil, then reacted with sulphanilamide in acidic conditions to form a diazo compound that coupled with N-1-naphylethylenediamide dihydrochloride to form a reddish-purple azo dye. With this method nitrite interference cannot be eliminated and consequently the parameter measured is nitrate plus nitrite.
Nitrite: As for nitrate without the reduction step.
Phosphate: Reduction of a phosphomolybdate complex in acid solution to 'molybdenum blue' by ascorbic acid with sensitivity enhanced by the catalytic action of antimony potassium tartrate.
Silicate: Reduction of silicomolybdate solution to 'molybdenum blue' by ascorbic acid with the addition of oxalic acid to eliminate interference from phosphates.
Ammonia: The method for ammonia was the production of an indophenol blue complex at optimum pH (10.6) and temperature (55 C).
Urea: Urea was directly determined by the addition of diacetyl monoxime in the presence of an FeCl3 catalyst.

In all cases the colorimeter output was as a voltage to a chart recorder which was tapped off and logged automatically at 1 minute intervals.

Calibration was achieved by running four standard concentrations through the system once or twice a day. Distilled water washes were passed through the system at approximately six-hourly intervals.

The data were subdivided into segments using the analyst's notes and the chart records for which the baseline was linear and a single calibration curve applied.

The processing system computed a baseline drift equation for each segment and, in a second pass, stripped off the baseline. Calibration equations were computed and applied to each segment. The calibration program additionally converted all baseline and standard flags to suspect.

Silicate required an additional processing step prior to baseline correction. Running a distilled water wash caused the silicate signal voltage to drop, sometimes by as much as 100 per cent. This voltage drop was assumed to be a linear drift between baselines and corrected on this basis.

Post-processing quality control comprised checking time series plots for any spikes which have been overlooked and checking the concentrations computed for the standards.

The internal processes of an autoanalyser involve considerable delays between the collection of a water sample and the logging of the data point for that sample. Time corrections were applied to synchronise nitrate to salinity and the other three nutrients to nitrate.


Chlorophyll concentrations were measured using an Aquatracka logarithmic response fluorometer mounted in a light-tight box on the starboard deck.

The fluorometer was calibrated by regressing the natural log of chlorophyll concentration against fluorometer voltage. No chlorophyll samples were taken on this cruise, so the fluorometer was 'calibrated' using data from Challenger 39. Chlorophyll concentrations were thus computed using the equation:

Chlorophyll (mg m-3) = exp(1.8300*fluorometer voltage-4.0700) (n=130;r2=75.8%)

Sea surface temperature and salinity

Temperature and salinity were measured using an autoranging TSG103 thermosalinograph. Temperature was measured by a thermistor in the non-toxic supply inlet manifold. Conductivity was measured by a unit in the ship's wet laboratory, which included a second thermistor to provide temperature for the computation of salinity.

The thermosalinograph was intercalibrated against surface values taken from the calibrated CTD. The corrections applied to the thermosalinograph and the time period for which they are valid are shown below:

Start time End time Salinity Correction (PSU) Temperature Correction (°C)
04/04/1990 08:20 02/05/1990 15:22 0.05 0.00

Optical Attenuance and Sediment Load

Optical transmittance was measured using a SeaTech red light (661nm) transmissometer with a 25cm optical path length mounted in a light-tight box on the starboard deck.

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 attenuance to eliminate the influence of instrument path length using the equation:

Attenuance = -4.0 * loge (voltage/5.0)

Attenuance was regressed against total suspended matter determinations to derive the equation below to allow attenuance to be expressed as suspended matter:

Total suspended matter (mg/l) = (Attenuance-0.6075)/0.4341 (n=114;r2=86.9%)


Grasshof, K., Erhardt, M. and Kremling, K. (1983). Methods of sea water analysis , 2nd edition. Verlag Chemie, Weinheim, 419pp..

CH64 Sea surface Hydrography, Meteorology and Navigation Series


A suite of parameters were logged from the non-toxic supply, the intake for which was located on the ship's hull, about 2m below the surface.

Operational procedure and data logging

Data were logged by the Research Vessels Services ABC data logging system. The data output units were sampled every 30 seconds by a microprocessor interface (the Level A) which passed time stamped data cycles to a Sun workstation (the Level C) via a buffering system (the Level B). Navigation was updated every two minutes and infilled by linear interpolation. Dissolved oxygen and probe temperature were logged at 15 minute intervals by a PC connected to the Endico controller and transferred to the Level C on floppy disk.

Data Processing

The raw data comprised ADC counts. These were converted into engineering units (degrees for latitude/longitude, volts for PAR meters, fluorometer, transmissometer and nutrients, mmho/cm for conductivity, degC for temperature, metres for bathymetry) by the application of laboratory determined calibrations and salinity was calculated using the algorithm in Fofonoff and Millard (1983). The data were submitted to BODC in this form.

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.

Data Activity or Cruise Information


Cruise Name CH64
Departure Date 1990-04-03
Arrival Date 1990-05-03
Principal Scientist(s)Nicholas J P Owens (Plymouth Marine Laboratory)
Ship RRS Challenger

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
Q value below limit of quantification