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Metadata Report for BODC Series Reference Number 894752


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type Acoustic doppler current profiler
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Scottish Association for Marine Science
Processing Status QC in progress
Online delivery of data Download not available
Project(s) Oceans 2025 Theme 10 SO4
 

Data Identifiers

Originator's Identifier SUR34016
BODC Series Reference 894752
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2009-06-25 04:34
End Time (yyyy-mm-dd hh:mm) 2009-06-26 04:33
Nominal Cycle Interval 120.0 seconds
 

Spatial Co-ordinates

Start Latitude 56.68533 N ( 56° 41.1' N )
End Latitude 56.60633 N ( 56° 36.4' N )
Start Longitude 6.28450 W ( 6° 17.1' W )
End Longitude 7.66250 W ( 7° 39.7' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 17.0 m
Maximum Sensor or Sampling Depth 809.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
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 Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum -
 

Parameters

BODC CODERankUnitsTitle
DBINAA010MetresDepth (spatial coordinate) of ADCP bin relative to water surface {bin depth} in the water body
ZZZZZZ010DimensionlessDummy channel
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ACYCAA011DimensionlessSequence number
ALATTR011DegreesLatitude north relative to WGS84 by Trimble GPS
ALONTR011DegreesLongitude east relative to WGS84 by Trimble GPS
APEWTR012Centimetres per secondEastward velocity of measurement platform relative to ground surface by Trimble GPS
APNSTR012Centimetres per secondNorthward velocity of measurement platform relative to ground surface by Trimble GPS
ASAMSP002DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 1
ASAMSP022DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 2
ASAMSP032DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 3
ASAMSP042DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 4
LCEWAS012Centimetres per secondEastward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)
LCNSAS012Centimetres per secondNorthward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)
LERRAS012Centimetres per secondError velocity of water current in the water body by shipborne acoustic doppler current profiler (ADCP)
LREWAS012Centimetres per secondEastward velocity of water current relative to moving platform in the water body by shipborne acoustic doppler current profiler (ADCP)
LRNSAS012Centimetres per secondNorthward velocity of water current relative to moving platform in the water body by shipborne acoustic doppler current profiler (ADCP)
LRZAAS012Centimetres per secondUpward velocity of water current in the water body by shipborne 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

No Problem Report Found in the Database

Data Quality Report

The relative eastward and northward current velocity channels (LREWAS01 and LRNSAS01) show a large amount of variability when the ship is travelling at relatively high speeds. The absolute eastward and northward current velocities (LCEWAS01 and LCNSAS01) are derived using the relative current velocities and therefore inherit this variability from the parent data.

These data channels have not been flagged but the end user should be made aware that such variability exists.


Data Access Policy

Data Access Policy information not available. Assume data are Restricted


Narrative Documents

D340A 75kHz VMADCP processing

Configuration

The 75 kHz ADCP on board the RRS Discovery is an Ocean Surveyor broad band phased array VMADCP mounted in the hull in a second water chest 4.15 m forward and 2.5 m to the starboard of the 150kHz well which is situated 1.75 m to the port of the keel and 33 m aft of the bow at the water line. The VMADCP was configured to sample over 120 second intervals with 100 bins of 8 m depth and a blank beyond transmit of distance of 8 m. The VMADCP was configured to run in 'Narrowband' range over resolution mode with bottom tracking used over the Icelandic and UK continental shelves.

Data Originator's Processing

  • Data acquisition

    Data were processed using the following scripts:

    • s75exec0: data read into Pstar format from the raw RDI binary format file; Water track velocities written into 'sur' files and bottom track into 'sbt' files whilst in bottom track mode; Velocities scaled to cm/s and amplitudes by 0.45 into db; Time variable corrected to GPS time by combining the PC clock time and the PC-GPS; perform nominal edits and adjust bin depths to correct levels.

    • s75exec1: data edited according to status flags (velocity data replaced with absent data if variable '2+bmbad' was greater than 25%); Time of ensemble moved to the end of ensemble period.

    • s75exec2: merged data with Ashtech-a ghdg; ADCP velocities converted to speed and direction allowing heading correction to be applied; ADCP velocities returned to east and north components.

    • s75exec3: applied misalignment angle ø and scaling factor A.

    • s75exec4: merged ADCP data with the bestnav data. Ship's velocity calculated from spot positions and applied to ADCP velocity producing absolute velocity of the water; Time base of ADCP profiles shifted to the centre of the 2 minute ensemble by subtracting 60 seconds.

  • Calibration

    Calibration was achieved by using bottom tracking data made available after departure from Reykjavík across the Icelandic continental shelf. Using long, straight and steady speed sections of standard 2 minute ensemble profiles over reasonably constant depths the following calibrations for misalignment angle, ø, and necessary amplification (tilt), A, were derived;

    ø A
    Mean 0.03462772 1.001979978
    SD 0.14342535 0.002759036

BODC post-processing and screening

  • Reformatting

    The data were converted from P* format into BODC internal format (QXF) to allow use of in-house visualisation tools.

  • Screening

    Reformatted data were visually checked using the in-house editor EDSERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated quality control flag to 'M' for suspect values and 'N' for nulls.

  • Banking

    Once quality control screening was complete, the data were archived in the BODC National Oceanographic Database and the associated metadata were loaded into an ORACLE Relational Database Management System.


Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 4: The Extended Ellett Line

The Ellett Line (begun in 1975 and since 1996 the Extended Ellett Line from Scotland to Iceland) crosses important north Atlantic Meridional Overturning Circulation (MOC) components and thus provides an additional contribution to understanding the north Atlantic response to climate change. Sustained Observation Activity (SO) 4 will repeat this section annually collecting a wide variety of physical and biogeochemical measurements, and will, to enhance the time variable component, make use of Argo floats and gliders. SO 4 will be implemented by physical, biological and chemical scientists at the National Oceanography Centre, Southampton (NOCS) and the Scottish Association for Marine Science (SAMS).

SO 4 formally contributes to the Department for Environment, Food and Rural Affairs (DEFRA)-funded Marine Environmental Change Network (MECN). Established in 2002 to coordinate and promote the collection and utilisation of marine time-series and long-term data sets, the goal of the network is to use long-term marine environmental data from around the British Isles and Ireland to separate natural fluctuations from global, regional and local anthropogenic impacts.

The specific deliverables for SO 4 are:

  • A time series of the evolution of the hydrography of the northeast Atlantic, together with a more formal understanding of the causes of any changes observed
  • An archived data set available to the international community via the British Oceanographic Data Centre (BODC)
  • A platform for further scientific research

More detailed information on this Work Package is available at pages 15 - 16 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/


Data Activity or Cruise Information

Cruise

Cruise Name D340A
Departure Date 2009-06-10
Arrival Date 2009-06-25
Principal Scientist(s)Toby J Sherwin (Scottish Association for Marine Science)
Ship RRS Discovery

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