Metadata Report for BODC Series Reference Number 489782
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
SeaDataNet Quality Flags
Metadata Summary
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Time Co-ordinates(UT) |
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Problem Reports
The position of this deployment is approximate because the instrument was relocated by trawling and found adrift.
There is some discernable reduction in data quality in the form of increasing noise in bins 11-14 (shallower than 77m).
Noise levels were excessive in all bins at times on February 26th and 27th 1996. Periods of data up to six hours duration have been flagged out completely as a result.
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:
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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.
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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.
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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) | 1996-02-22 |
End Date (yyyy-mm-dd) | 1996-04-19 |
Organization Undertaking Activity | Proudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool) |
Country of Organization | United Kingdom |
Originator's Data Activity Identifier | POLRIG#758 |
Platform Category | fixed benthic node |
Proudman Oceanographic Laboratory Moored Instrument Rig#758
This rig was deployed as part of the LOIS Shelf-Edge Study.
The deployment commenced as Rig#750 at site S400. The rig was relocated by trawler activity on 22nd February 1996. Data following this event were treated as a separate station, which was given the designation Rig#758.
Recovery commenced when the release was fired from the ship on station S400 but the instrument could not be located on the surface. It was found adrift at station S140 the following day. The position held in the database is therefore a 'best guess' based on the following known information:
- The instrument must have been relocated to the south to drift to S140.
- The instrument was relocated to a water depth of 259m.
- The instrument was within 5km of S400 for the release to have fired.
This position is believed to be the centre of a 2.5km radius circle within which the instrument was located for the duration of the record.
Rig position | 56° 25.00' N 09° 05.00' W |
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Deployed | Repositioned by trawling activity on 22 Feb 1996 |
Released | Release fired on 19 Apr 1996 |
Recovered | Found adrift at S140 by RRS Challenger on 20 Apr (Cruise CH126A) |
Instruments deployed on the rig
Height above Sea Bed | Instrument |
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0.5m | RDI Acoustic Doppler Current Profiler (#1567) |
Cruise
Cruise Name | CH125B |
Departure Date | 1996-02-13 |
Arrival Date | 1996-03-03 |
Principal Scientist(s) | A Edward Hill (University of Wales, Bangor School of Ocean Sciences) |
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 |
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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 |
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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 |