Metadata Report for BODC Series Reference Number 491891

• 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

Problem Reports

It is possible that the rig moved at 10:45 on May 14th 1995 as indicated by pressure sensors on the rig.

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

TRB-1 and TRB-2 Self-recording Transmissometers

The TRB-1 self-recording transmissometer was designed by the School of Ocean Sciences, University of Wales, Bangor and was sometimes known as the 'Mark III Transmissometer'. The instrument was developed commercially by W.S. Ocean Systems Limited and marketed with the designation TRB-2.

The instrument used a 660nm (red) source modulated at 400 Hz. The optical assembly incorporated a folded beam design to reduce instrument size to a minimum. The light beam was collimated using an achromatic lens, passed through a fixed length of the water column and reflected back to a photodiode receiver via a prism reflector. The optical path length could be fixed at either 5 cm, 10 cm or 25 cm.

Data were logged at the top of each minute as the average of 200 samples taken at 400 Hz. Timing was based on an accurate real-time clock emulated by the processor BIOS extension. Data were acquired by a multi-channel 12- bit data acquisition system resident on the motherboard resulting in a count between 0 and 4095.

Data were stored internally on a 2 MByte SRAM card giving storage for 120 days of data. After deployment, the data were downloaded in a simple ASCII format onto a PC.

TRB-2 instruments could be fitted with additional conductivity and temperature sensors.

Data Processing: TR0001.683

Introduction

Calibration details for TRB1 transmissometer serial number 0001 deployed on POL mooring 683.

Calibration

Calibration from raw counts used the equation:

atten = -4 * ln ((counts - B)/C₀ - B)

where:

B = Blocked path counts (184)
C₀ = Number of counts corresponding to 5V (666.665)

C₀ was determined by calibration against the CTD transmissometer on cast CP20 during Charles Darwin cruise CD93A.

Data Validation

The calibrated data were checked against the following CTD casts on station S200.

Other casts were reported from CD93A between 21 May and 29 May 1995. However, it is believed that the mooring was trawled and cast adrift on 14 May 1995.

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.

Additional Information

This instrument was recovered adrift after the mooring had been damaged by trawling.

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

Proudman Oceanographic Laboratory Moored Instrument Rig #683

This rig was deployed as part of the LOIS Shelf-Edge Study at site S200.

The instruments were anchored by 1000kg of chain and kept erect by a 48" diameter buoy attached 20m below the sea surface.

Instruments deployed on the rig

• Instruments marked "*" were lost, probably due to trawling.
  The remainder of the mooring was recovered adrift.
  Probably moved at 10:45 on 14/05/1995.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

LOIS (SES) Mooring and CTD Site S200

Site S200 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

1996

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

Glossary

• CM = Current meter (Aanderaa or S4)
• BPR = Bottom pressure recorder
• ADCP = Acoustic Doppler Current Profiler
• TChn = Thermistor chain
• Tr = Transmissometer
• Fl = Fluorometer
• NA = Nutrient analyser

Note

1. Transmissometers may have been fitted to some of the current meters.
2. Other instruments (colour sensors, STABLE) may have been deployed.
3. Only periods for which useful data were returned are shown.

Related Fixed Station activities are detailed in Appendix 2

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: POLRIG#683

Related series for this Data Activity 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.

Appendix 2: LOIS(SES) S200

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.