Search the data

Metadata Report for BODC Series Reference Number 489770


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type Acoustic doppler current profiler
Instrument Mounting fixed benthic node
Originating Country United Kingdom
Originator -
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) Land Ocean Interaction Study (LOIS)
LOIS Shelf Edge Study (LOIS - SES)
 

Data Identifiers

Originator's Identifier rd1567.750
BODC Series Reference 489770
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1996-02-05 20:15
End Time (yyyy-mm-dd hh:mm) 1996-02-22 12:35
Nominal Cycle Interval 600.0 seconds
 

Spatial Co-ordinates

Latitude 56.45420 N ( 56° 27.3' N )
Longitude 9.08100 W ( 9° 4.9' W )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor or Sampling Depth 74.0 m
Maximum Sensor or Sampling Depth 378.0 m
Minimum Sensor or Sampling Height 18.0 m
Maximum Sensor or Sampling Height 322.0 m
Sea Floor Depth 396.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Sensor fixed with measurements made at multiple depths within a fixed range (e.g. ADCP) - 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 or Sampling 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
 

Parameters

BODC CODERankUnitsTitle
DBINAA010MetresDepth (spatial coordinate) of ADCP bin relative to water surface {bin depth} in the water body
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
LCEWAP012Centimetres per secondEastward velocity of water current (Eulerian measurement) in the water body by moored acoustic doppler current profiler (ADCP)
LCNSAP012Centimetres per secondNorthward velocity of water current (Eulerian measurement) in the water body by moored acoustic doppler current profiler (ADCP)
LERRAP012Centimetres per secondError velocity of water current in the water body by moored acoustic doppler current profiler (ADCP)
LRZAAP012Centimetres per secondUpward velocity of water current in the water body by moored acoustic doppler current profiler (ADCP)

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

The data contained a significant number of spikes. In bin 1 (the deepest at 378 m) to 15 (154 m) the spikes could easily be identified and have been flagged suspect. From bin 16 (138 m) and above, there was a noticable increase in the noise level, making flagging difficult or impossible. The noise level was consistent throughout the record with no readily identifiable quiet or noisy periods.

In bins 19 (90 m) and 20 (74 m) there was an unusually large proportion of zero values, possibly incorrectly set null values. These have all been flagged suspect.

It is recommended that data from bins shallower than 138 m (bins 16-20) are used with caution. The noise levels in bins shallower than 100 m (bins 19- 20) are unusually bad and users are advised against making any use of any of the data from these bins.


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

RDI Acoustic Doppler Current Profiler

Acoustic Doppler Current Profilers (ADCPs) use sound waves to determine vertical profiles of currents, and may be deployed fixed to the sea floor, attached to a surface buoy, mounted on the hull of a ship, towed behind a ship or lowered on a cable.

ADCPs transmit sound bursts into the water. Particles carried by the water currents scatter the sound back to the transducer. As echoes return from further ranges from the sensor, the instrument assigns different water depths to the returning signals. Motion of the scattering particles relative to the sound source causes a change in the frequency of the sound (known as Doppler shift). The ADCP measures this change to produce vertical profiles of water velocity at up to 128 depths throughout the water column.

Specifications:
number of depth cells 1 to 128;
size of depth cells 0.12 to 32.00 metres;
velocity range +/- 10 m/s.

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:

  • Irregularities such as unfeasible values
  • Inconsistencies between related information, for example:
    • Times for instrument deployment and for start/end of data series
    • Length of record and the number of data cycles/cycle interval
    • Parameters expected and the parameters actually present in the data cycles
  • Originator's comments on meter/mooring performance and data quality

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:

  • Spurious data at the start or end of the record.
  • Obvious spikes occurring in periods free from meteorological disturbance.
  • A sequence of constant values in consecutive data cycles.

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:

  • Maximum and minimum values of parameters (spikes excluded).
  • The occurrence of meteorological events.

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

Land Ocean Interaction Study (LOIS)

Introduction

The Land Ocean Interaction Study (LOIS) was a Community Research Project of the Natural Environment Research Council (NERC). The broad aim of LOIS was to gain an understanding of, and an ability to predict, the nature of environmental change in the coastal zone around the UK through an integrated study from the river catchments through to the shelf break.

LOIS was a collaborative, multidisciplinary study undertaken by scientists from NERC research laboratories and Higher Education institutions. The LOIS project was managed from NERC's Plymouth Marine Laboratory.

The project ran for six years from April 1992 until April 1998 with a further modelling and synthesis phase beginning in April 1998 and ending in April 2000.

Project Structure

LOIS consisted of the following components:

  • River-Atmosphere-Coast Study (RACS)
    • RACS(A) - Atmospheric sub-component
    • RACS(C) - Coasts sub-component
    • RACS(R) - Rivers sub-component
    • BIOTA - Terrestrial salt marsh study
  • Land Ocean Evolution Perspective Study (LOEPS)
  • Shelf-Edge Study (SES)
  • North Sea Modelling Study (NORMS)
  • Data Management (DATA)

Marine Fieldwork

Marine field data were collected between September 1993 and September 1997 as part of RACS(C) and SES. The RACS data were collected throughout this period from the estuaries and coastal waters of the UK North Sea coast from Great Yarmouth to the Tweed. The SES data were collected between March 1995 and September 1996 from the Hebridean slope. Both the RACS and SES data sets incorporate a broad spectrum of measurements collected using moored instruments and research vessel surveys.


LOIS Shelf Edge Study (LOIS - SES)

Introduction

SES was a component of the NERC Land Ocean Interaction Study (LOIS) Community Research Programme that made intensive measurements from the shelf break in the region known as the Hebridean Slope from March 1995 to September 1996.

Scientific Rationale

SES was devoted to the study of interactions between the shelf seas and the open ocean. The specific objectives of the project were:

  • To identify the time and space scales of ocean-shelf momentum transmission and to quantify the contributions to ocean-shelf water exchange by physical processes.

  • To estimate fluxes of water, heat and certain dissolved and suspended constituents across a section of the shelf edge with special emphasis on net carbon export from, and nutrient import to, the shelf.

  • To incorporate process understanding into models and test these models by comparison with observations and provide a basis for estimation of fluxes integrated over time and the length of the shelf.

Fieldwork

The SES fieldwork was focussed on a box enclosing two sections across the shelf break at 56.4-56.5 °N and 56.6-56.7 °N. Moored instrument arrays were maintained throughout the experiment at stations with water depths ranging from 140 m to 1500 m, although there were heavy losses due to the intensive fishing activity in the area. The moorings included meteorological buoys, current meters, transmissometers, fluorometers, nutrient analysers (but these never returned any usable data), thermistor chains, colour sensors and sediment traps.

The moorings were serviced by research cruises at approximately three-monthly intervals. In addition to the mooring work this cruises undertook intensive CTD, water bottle and benthic surveys with cruise durations of up to 6 weeks (3 legs of approximately 2 weeks each).

Moored instrument activities associated with SES comprised current measurements in the North Channel in 1993 and the Tiree Passage from 1995-1996. These provided boundary conditions for SES modelling activities.

Additional data were provided through cruises undertaken by the Defence Evaluation and Research Agency (DERA) in a co-operative programme known as SESAME.


Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1996-02-05
End Date (yyyy-mm-dd) 1996-02-22
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#750
Platform Categoryfixed benthic node

Proudman Oceanographic Laboratory Moored Instrument Rig#750

This rig was deployed as part of the LOIS Shelf-Edge Study at site S400

Rig position 56° 27.25'N 09° 04.86'W
Deployed 05 Feb 1996 20:10
from RRS Challenger (cruise CH125A)
Terminated 22 Feb 1996 12:40
by trawler activity (observed in record)

Instruments deployed on the rig

Height above
Sea Bed
Instrument
0.5m RDI Acoustic Doppler Current Profiler (#1567)

Cruise

Cruise Name CH125A
Departure Date 1996-01-31
Arrival Date 1996-02-12
Principal Scientist(s)M John Howarth (Proudman Oceanographic Laboratory)
Ship RRS Challenger

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameLOIS(SES) S400
CategoryOffshore location
Latitude56° 27.17' N
Longitude9° 4.85' W
Water depth below MSL397.0 m

LOIS (SES) Mooring and CTD Site S400

Site S400 was a fixed station where moorings were deployed during the Land-Ocean Interaction Study (LOIS) Shelf Edge Study (SES). It was also one of fourteen CTD sites on repeat section S, across the Hebridean Slope, occupied by cruises between March 1995 and September 1996.

Instrument Deployment History

The following tables summarise the instruments deployed at this site for which data may be available.

1995

Mar Apr May Jun Jul Aug Sep Oct Nov Dec
CM             a      
ADCP           a a b b b

1996

Jan Feb Mar Apr May Jun Jul Aug
CM                
ADCP c c d d       e

Each different letter in the tables above corresponds to an individual instrument record.

Glossary

  • CM = Current meter (Aanderaa or S4)
  • ADCP = Acoustic Doppler Current Profiler

Note

  1. Transmissometers may have been fitted to some of the current meters.
  2. Only periods for which useful data were returned are shown.

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: LOIS(SES) S400

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
444228Currents -subsurface Eulerian1995-08-12 08:52:2956.453 N, 9.0807 WRRS Challenger CH121A
431389Currents -subsurface Eulerian1995-08-15 15:52:3056.4507 N, 9.0808 WRRS Challenger CH121A
444253Currents -subsurface Eulerian1995-09-06 07:55:0056.4532 N, 9.0807 WRRS Challenger CH121C
444265Currents -subsurface Eulerian1995-12-06 09:25:0056.454 N, 9.0808 WRRS Challenger CH123B
477222Currents -subsurface Eulerian1996-07-14 15:27:3856.455 N, 9.0818 WRRS Challenger CH128A