Metadata Report for BODC Series Reference Number 541926

Metadata Summary

Data Description

Data Category Water column chemistry
Instrument Type
EnviroTech LLC NAS-2E Nutrient Analyser  nutrient analysers
Instrument Mounting moored surface buoy
Originating Country United Kingdom
Originator -
Originating Organization Scottish Association for Marine Science
Processing Status banked
Project(s) Provess

Data Identifiers

Originator's Identifier nas1714_823
BODC Series Reference 541926

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1999-04-02 21:01
End Time (yyyy-mm-dd hh:mm) 1999-04-26 13:01
Nominal Cycle Interval 7200.0 seconds

Spatial Co-ordinates

Latitude 52.29800 N ( 52° 17.9' N )
Longitude 4.29970 E ( 4° 18.0' E )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor Depth 1.0 m
Maximum Sensor Depth 1.0 m
Minimum Sensor Height 18.0 m
Maximum Sensor Height 18.0 m
Sea Floor Depth 19.0 m
Sensor Distribution Sensor fixed, measurements made at fixed depths - The sensor is at a fixed depth, but measurements are made remotely from the sensor over a range of depths (e.g. ADCP measurements)
Sensor Depth Datum Sea floor reference - Depth measured as a height above sea floor but converted into a depth relative to the sea surface according to the same datum as used for sea floor depth (applicable to instrument depths not bathymetric depths)
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface


BODC CODE Rank Units Short Title Title
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
NTRZNS01 1 Micromoles per litre NO3+NO2_Unfilt_Colin-Situ Concentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ nutrient analysis system

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

NAS-2E in situ Nutrient Analyser

The NAS-2E in situ Nutrient Analyser is a submersible instrument for the automated measurement of dissolved nutrient concentrations in marine and fresh waters. It employs colorimetric wet-chemistry to determine nutrient concentrations by measuring the light absorbance of a coloured dye produced by a chemical reaction. The instrument, manufactured by WS Ocean Systems Ltd., Hans, UK, is designed for deployment on moorings. Versions have been developed for nitrate+nitrite, phosphate and silicate. The use of standard wet-chemistry techniques ensure comparability with laboratory results.

References for manufacturer's standard chemical methods are:

although these may be altered by the user.

The system utilizes a syringe pump and rotary valve to acquire and react discrete water samples. For nitrate+nitrite analysis, the samples is first passed over a copper-cadmium column to reduce nitrate to nitrite before reacting with the reagents to form the dye. Once the reaction takes place the sample is injected into the colorimeter where optical beam attenuation is measured. An integral system controller drives the syringe and valve via stepper motors and records the colorimeter readings.

The analysis routines include blank measurements for turbidity and optical fouling. An on-board calibration standard is periodically analysed to ensure the continuous integrity of the results. Programmable controls allows the operator to develop and program alternative chemical routines. All raw data are recorded as voltages representing beam transmission through the sample within the colorimeter pathlength. Following recovery of the instrument, raw data are downloaded to a PC and converted to absorbance units and nutrient concentration using manufacturer's calibration and on- board blank and standard readings.

Manufacturer's specification:

Wavelength 560 nm 880 nm
Accuracy 2% of range 5% of range
Sensitivity 0.5% of range 2.5% of range

Level of detection (PL = colorimeter path length):

Nitrate (µM) 0-300 with 5 mm PL
  0-60 with 10 mm PL
  0-10 with 20 mm PL
  0-5 with 40 mm PL
Silicate (µM) 0-60 with 10 mm PL
  0-10 with 20 mm PL
Phosphate (µM) 0-3 with 20 mm PL
  0-1 with 40 mm PL

Data Processing Notes

Data processing was carried out at the Dunstaffnage Marine Laboratory, Oban, UK. The instrument voltages were corrected for blank readings and converted to absorption according to the formula:

[Absorbance] = log 10 ([blank voltage]/[sample voltage])

Absorption readings were then converted to concentrations by calibration against calibration samples from an on-board standard taken every 6 samples during the deployment according to the formula:

[Concentration, µM] = [sample absorbance]/([standard absorbance]*[standard concentration, µM])

The on-board standard concentration was 10 µM of nitrite.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

PROcesses of Vertical Exchange in Shelf Seas (PROVESS)


PROVESS was an interdisciplinary study of the vertical fluxes of properties through the water column and the surface and bottom boundary layers. The project was funded by the European Community MAST-III programme (MAS3-CT97- 0159) and ran from March 1998 to May 2001.

Scientific Rationale

PROVESS was based on the integration of experimental, theoretical and modelling studies with the aim of improving understanding and quantification of vertical exchange processes in the water column, in particular in the surface and benthic boundary layers and across the> pycnocline. PROVESS also explored mechanisms of physical-biological coupling in which vertical exchanges and turbulence significantly affect the environmental conditions experienced by the biota with particular reference to aggregation, flocculation, sedimentation and trophic interactions.


The experimental phase of the project was carried out at two contrasting sites in the North Sea: the northern North Sea site (NNS) and the southern North Sea site (SNS).

The two sites had the following characteristics:

Position 52° 15.0' N, 4° 17.0' E 59° 20.0' E, 1° 00.0' E
Time of year April-May September-November
Water depth (m) 16 100
M2 max amplitude (m s-1) 0.75 0.15
Max current (m s-1) 1.0 0.6
Delta T (deg C) mixed 7-1
Thermocline depth (m) mixed 35-100
Delta S 1 small
Halocline depth (m) 5-10 cf. thermocline depth
Max wind speed (m s-1) 20 25
Max wave height (m) 5 10
Max wave period (s) 8 10
Internal motion No Yes
Sediment muddy-sand muddy-sand
Biology eutrophic oligotrophic

At both locations measurements were concentrated at a central position with additional measurements being made to estimate horizontal gradients. Moored instruments (including current meters, temperature and pressure sensors, fluorometers, transmissometers, nutrient analysers and meteorological sensors) were deployed between 7 September and 5 November 1998 at the NNS and between 29 March and 25 May 1999 at the SNS. Each experiment was supported by intensive measurement series made from oceanographic ships and involving turbulence dissipation profiler CTD, particle size profilers, optical profilers, benthic sampling and water bottle sampling.

Details of the cruises were as follows:

Site Ship
NNS Valdivia (GER) VA174 5 - 17 Sep 1998
  Dana (DK) D1198 14 - 26 Oct 1998
  Pelagia (NL) PE125 19 - 30 Oct 1998
  Challenger (UK) CH140 22 Oct - 9 Nov 1998
SNS Pelagia (NL) PE135 29 Mar - 9 Apr 1999
  Mitra (NL) MT0499 19 - 30 Apr 1999
  Belgica (BE) BG9912 17 - 21 May 1999

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1999-03-29
End Date (yyyy-mm-dd) 1999-05-18
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#823
Platform Categorymoored surface buoy


This mooring was known within PROVESS as 'Rig G', but was sometimes referred to as the 'surface environmental mooring'. It was one of a cluster of moorings deployed at the main focus of the Southern North Sea Site during the spring of 1999.

Mooring type Surface toroid with sub-surface instrument cage.
(1 m below surface)
TRB-2 transmissometer (S/N 1761)
DML NAS nitrate analyser (S/N 1714)
DML fluorometer (S/N 012)

Other Series linked to this Data Activity - 541902 541809


Cruise Name PE136
Departure Date 1999-03-29
Arrival Date 1999-04-09
Principal Scientist(s)Hans van Haren (Royal Netherlands Institute for Sea Research)
Ship RV Pelagia

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NamePROVESS Southern North Sea Site
CategoryOffshore area
Latitude52° 18.00' N
Longitude4° 18.00' E
Water depth below MSL16.0 m

PROVESS Southern North Sea Site

Eleven mooring packages were deployed at PROVESS Southern North Sea site by Pelagia cruise PE136 in March 1999. One of these (Rig U) was lost, the NIOZ mooring was recovered by PE136 in April 1999 and the remaining nine were recovered by either RV Belgica cruise BG9912 (8 moorings) or RV Zirfea (Rig V) in May 1999.

The layout of the mooring array was:

BODC image

The asterisk represents an array of five moorings as detailed in the inset map.

Mooring data

The data returned from each rig were as follows:

Rig identifier Data
A POLRIG#820 Near-bed currents
Temperature, salinity and attenuance
B POLRIG#821 ADCP currents
Water level
Thermistor plus conductivity chain
D POLRIG#822 Currents
H POLRIG#824 Currents
Nutrients (nitrate + nitrite, silicate)
G POLRIG#823 Surface attenuance, nutrients (nitrate + nitrite) and chlorophyll
NIOZ   ADCP currents
Thermistor chain
Wave statistics (considered suspect)
V POLRIG#827 Currents
Temperature (4 depths)
Y POLRIG#829 Water level
Near-bed temperature
T POLRIG#825 ADCP currents
Water level
Thermistor plus conductivity chain
U Unknown None
X POLRIG#828 Water level
Near-bed temperature

CTD data

A total of 356 CTD casts were also collected during the three cruises surveying this area. These include:

Cruise identifier Cruise dates No. of CTD casts
RV Pelagia (#136) 29 March - 09 April 1999 133
Mitra (#0499) 19 April - 30 April 1999 170
RV Belgica (#9912) 17 May - 21 May 1999 53

Additonal data

Supporting meteorological data (including sea surface temperature and wave statistics) from two platforms (52° 33' N, 4° 3.5' E and 52° 16.4' N, 4° 17.8' E) were supplied to the project and are held by BODC. These series run from the beginning of March 1999 until the end of May 1999.

Other Series linked to this Fixed Station for this cruise - 529245 529257 529269 529270 529282 529294 529301 529313 529325 529337 529349 529350 541730 541742 541754 541766 541778 541791 541809 541810 541822 541834 541846 541858 541871 541895 541902 541938 553141 553294 553301 553313 564243

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