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Metadata Report for BODC Series Reference Number 496176


Metadata Summary

Data Description

Data Category Transmittance/attenuance, turbidity, or SPM conc.
Instrument Type Transmissometer
Instrument Mounting subsurface mooring
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 tr1761.769
BODC Series Reference 496176
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1996-04-18 16:36
End Time (yyyy-mm-dd hh:mm) 1996-07-17 14:32
Nominal Cycle Interval 60.0 seconds
 

Spatial Co-ordinates

Latitude 56.47020 N ( 56° 28.2' N )
Longitude 9.16330 W ( 9° 9.8' W )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor or Sampling Depth 1.0 m
Maximum Sensor or Sampling Depth 1.0 m
Minimum Sensor or Sampling Height 697.0 m
Maximum Sensor or Sampling Height 697.0 m
Sea Floor Depth 698.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
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
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ATTNMR011per metreAttenuation (red light wavelength) per unit length of the water body by 20 or 25cm path length transmissometer
CNDCPR011Siemens per metreElectrical conductivity of the water body by in-situ conductivity cell
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPPR011Degrees CelsiusTemperature of the water body

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 salinity data do not appear credible, and have all been flagged suspect.

Towards the end of the record, the attenuance signal increased dramatically indicating fouling of the optics or flattening of the battery. All affected data have been flagged suspect.


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: TR1761.769

Introduction

Calibration details for TRB2 transmissometer serial number 1761 deployed on POL mooring 769.

Calibration

Attenuance

Calibration from raw counts used the equation:

atten = -4 * ln ((counts - B)/C0 - B)

where:
B = Blocked path counts (4)
C0 = Number of counts corresponding to 5V (4812.49)

The instrument was calibrated by attaching it to the CTD frame during a cast.

Data Validation

The following comparisons were made between the CTD and TRB data during the deployment:

Cast Date/Time CTD Atten TRB Atten
CP71.CH126B 29/04/1996 23:39 0.963 0.935
CP72.CH126B 30/04/1996 01:22 0.991 0.932
CP74.CH126B 30/04/1996 05:03 0.822 0.899
CP77.CH126B 30/04/1996 15:30 0.949 1.038
CP133.CH126B 05/05/1996 07:52 0.892 1.069
CP191.CH126B 11/05/1996 00:54 0.708 1.018

Temperature

The temperature calibration applied was:

T = 18.506785 + 15.381837*X + 1.692264*X2 + 0.527669*X3

where:

X = (2*counts-4000)/2000

This is based on an instrument calibration done at POL just prior to the SES project.

Comparison with CTD data showed the TRB temperature to be 0.4-0.45 degrees low.

Conductivity

The conductivity calibration applied was:

C = 4.26171 + 0.0190272*X - 4.80270E-06*X2 + 1.53658E-09*X3

where:

X = conductivity channel count

The conductivity sensor was obviously malfunctioning during this deployment and consequently comparison with CTD data is meaningless.

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) 1996-04-18
End Date (yyyy-mm-dd) 1996-07-29
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#769
Platform Categorysubsurface mooring

Proudman Oceanographic Laboratory Moored Instrument Rig #769

This rig was deployed as part of the LOIS Shelf-Edge Study at site S700.

Rig position: 56° 28.21'N 09° 09.80'W
Deployed: 18 Apr 1996 16:53
from RRS Challenger (cruise CH126A)
Recovered: 29 Jul 1996 09:32
onto RRS Challenger (cruise CH128B)

The instruments were anchored by a 500kg clump and suspended from a toroidal buoy on the surface.

Instruments deployed on the rig

Height above
Sea Bed
Instrument
1m WS Oceans transmissometer (#1761)
1m NAS2 Nutrient analyser (#1752)
1m Colour sensor (CS4-22)
3m to 43m 40m thermistor chain (#2330)

Related Data Activity activities are detailed in Appendix 1

Cruise

Cruise Name CH126A
Departure Date 1996-04-11
Arrival Date 1996-04-26
Principal Scientist(s)Paul Tett (Napier University School of Life Sciences)
Ship RRS Challenger

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameLOIS(SES) S700
CategoryOffshore location
Latitude56° 27.14' N
Longitude9° 9.50' W
Water depth below MSL700.0 m

LOIS (SES) Mooring and CTD Site S700

Site S700 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   b b b b c      
TChn     a a a a b      
Tr     a a            
Fl     a a b b c      
NA     a a b b        

1996

Jan Feb Mar Apr May Jun Jul Aug
CM   d d d e e e e
TChn   c c c d d d d
Tr                
Fl         d d d d
NA                

Each different letters in the table 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) 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:

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: POLRIG#769

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.

Series IdentifierData CategoryStart date/timeStart positionCruise
442560Hydrography time series at depth1996-04-18 17:00:0056.4702 N, 9.1633 WRRS Challenger CH126A
506098PAR radiance and irradiance1996-04-19 12:11:0056.4702 N, 9.1633 WRRS Challenger CH126A

Appendix 2: LOIS(SES) S700

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
496115Transmittance/attenuance, turbidity, or SPM conc.1995-03-27 18:20:4056.4517 N, 9.1585 WRRS Charles Darwin CD91B
439195Currents -subsurface Eulerian1995-03-29 10:38:0056.4622 N, 9.1613 WRRS Charles Darwin CD91B
436161Currents -subsurface Eulerian1995-03-29 10:55:0056.4622 N, 9.1613 WRRS Charles Darwin CD91B
496103Transmittance/attenuance, turbidity, or SPM conc.1995-05-10 20:00:0056.4532 N, 9.158 WRRS Charles Darwin CD93A
476218Fluorescence or pigments1995-05-10 20:02:5656.4532 N, 9.158 WRRS Charles Darwin CD93A
439619Hydrography time series at depth1995-05-10 20:30:0056.4532 N, 9.158 WRRS Charles Darwin CD93A
476114Fluorescence or pigments1995-05-11 13:02:5756.4605 N, 9.1642 WRRS Charles Darwin CD93A
439552Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439681Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439785Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
426098Currents -subsurface Eulerian1995-05-11 13:32:3056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431236Currents -subsurface Eulerian1995-05-11 13:44:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431297Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431457Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439251Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439263Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
390247CTD or STD cast1995-07-27 14:35:0056.4812 N, 9.1477 WRRS Challenger CH120
1287248Water sample data1995-07-27 14:35:0056.4812 N, 9.1477 WRRS Challenger CH120
476126Fluorescence or pigments1995-08-13 15:02:5756.4602 N, 9.1627 WRRS Challenger CH121A
426105Currents -subsurface Eulerian1995-08-13 16:42:3056.4602 N, 9.1625 WRRS Challenger CH121A
431248Currents -subsurface Eulerian1995-08-13 16:55:0056.4602 N, 9.1625 WRRS Challenger CH121A
439275Currents -subsurface Eulerian1995-08-13 16:55:0056.4602 N, 9.1625 WRRS Challenger CH121A
431304Currents -subsurface Eulerian1995-08-13 16:56:0056.4602 N, 9.1625 WRRS Challenger CH121A
439693Hydrography time series at depth1995-08-13 17:03:0056.4602 N, 9.1625 WRRS Challenger CH121A
439797Hydrography time series at depth1995-08-13 17:15:0056.4602 N, 9.1625 WRRS Challenger CH121A
439564Hydrography time series at depth1995-08-14 17:03:0056.4602 N, 9.1625 WRRS Challenger CH121A
436277Currents -subsurface Eulerian1996-02-05 17:45:0556.4648 N, 9.1635 WRRS Challenger CH125A
442443Hydrography time series at depth1996-02-05 18:00:0056.4648 N, 9.1635 WRRS Challenger CH125A
442406Hydrography time series at depth1996-02-05 18:00:0456.4648 N, 9.1635 WRRS Challenger CH125A
442431Hydrography time series at depth1996-02-05 18:00:0456.4648 N, 9.1635 WRRS Challenger CH125A
436204Currents -subsurface Eulerian1996-02-05 18:15:0456.4648 N, 9.1635 WRRS Challenger CH125A
442480Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442523Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442535Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
476187Fluorescence or pigments1996-04-18 14:02:5656.4617 N, 9.1625 WRRS Challenger CH126A
438917Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
438930Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
438942Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439017Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439459Currents -subsurface Eulerian1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A
442511Hydrography time series at depth1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A
442560Hydrography time series at depth1996-04-18 17:00:0056.4702 N, 9.1633 WRRS Challenger CH126A
506098PAR radiance and irradiance1996-04-19 12:11:0056.4702 N, 9.1633 WRRS Challenger CH126A