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Metadata Report for BODC Series Reference Number 576674

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) LOIS River-Atmosphere-Coast Study (RACS)

Data Identifiers

Originator's Identifier tr0004.637
BODC Series Reference 576674

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1993-12-12 10:10
End Time (yyyy-mm-dd hh:mm) 1993-12-17 13:43
Nominal Cycle Interval 3600.0 seconds

Spatial Co-ordinates

Latitude 53.79830 N ( 53° 47.9' N )
Longitude 0.04670 E ( 0° 2.8' E )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor or Sampling Depth 18.0 m
Maximum Sensor or Sampling Depth 18.0 m
Minimum Sensor or Sampling Height 1.0 m
Maximum Sensor or Sampling Height 1.0 m
Sea Floor Depth 19.0 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


BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ATTNZR011per metreAttenuation (red light wavelength) per unit length of the water body by transmissometer
TSEDTR011Milligrams per litreConcentration of suspended particulate material {SPM} per unit volume of the water body [particulate >unknown phase] by in-situ optical attenuance measurement and calibration against sample data

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

Data are noisy during events where beam attenuation/SPM concentration is elevated.

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: TR0004.637


Calibration of raw counts into beam attenuation used the equation:

Beam attenuation (/m) = -1/R * LN ((counts - BP)/(C0 - BP))


R is the pathlength (m) of the instrument (0.25)
BP is the blocked path counts (276.1)
C0 is the count value corresponding to 5V (969.69)

C0 was determined by calibration against the CTD transmissometer on cast CTD1 during cruise CH108B.

Suspended Load

Water samples from the CTD rosette were filtered during some cruises to determine SPM concentration. The concentrations were then regressed against the concurrent beam attenuation measured by the CTD transmissometer, yielding a slope (A1) and an intercept (A0). Beam attenuation was converted into SPM concentration using calibration coefficients determined by UNW:

SPM (mg/l) = (Beam attenuation - A0)/A1


A0 = -0.8188
A1 = 0.22859

Data Quality Check

It was not possible to check the calibrated beam attenuation data against the CTD transmissometer as no casts occurred at this site during the mooring deployment period.

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:

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:

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:

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.

LOIS (RACS) Holderness Experiment Data Collection and Processing

Data Collection and Processing - Waveriders

Datawell waverider buoys were deployed at sites N1, N2 and N3 with the buoys at the latter two sites recording directional data. Due to the shallow depths one rubber cord was used in each mooring, whereas two are recommended by Datawell to reduce mooring effects. Datawell waverider buoys calculate spectra and mean wave parameters on board before transmission to a shore station for storage (Datawell, 1995). Eight consecutive 200 second blocks are averaged after spectral analysis. The first and last 32 samples out of a total of 256 are tapered with a cosine taper and the taper is corrected for after averaging. Peak frequency and quality control flags were computed from the spectra. Quality control checks gave 2 per cent high frequency flags at N2 and 1 per cent at N3, with very few low frequency flags.

The recorded time for N1 data is the start of the burst, while the recorded time for N2 and N3 data is the time of receipt of transmission (approximately 40 minutes after the start time of the burst).

Data Collection and Processing - Pressure Recorders

Pressure wave recorders were mounted at 0.35m above the sea bed on PMPs (POL monitoring packages) deployed at stations N1 - N4 and S1 - S4. The pressure recorders used consisted of a pressure sensor in a standard Aanderaa casing. An oil-filled capillary tube was attached to the diaphragm housing to reduce flow effects on the sensor. Burst data were recorded at 2Hz for 20 minutes every 3 hours. Wolf gives details of the processing and correction procedures used on these data.

Data Collection and Processing - S4 Current Meters

InterOcean S4 current meters were mounted at 0.8m above the sea bed on PMPs (POL monitoring packages) deployed at stations N1 - N3 and S1 - S4. The current meters at the inner stations (N1 and S1) included a pressure sensor which allowed directional wave measurements to be made. this version of the S4 is referred to as the S4DW. The standard S4 meters measured 1 minute bursts of data while the S4DWs measured 20 minute bursts at 2Hz with consecutive samples averaged to give 1Hz output.

General Information

Winds were observed at three coastal locations. The observed local wind regime clustered about directions 000 degrees and 200 degrees with maximum speeds of 11.2 m/s and 17.4 m/s respectively.

Repeated CTD profiles were obtained for stations N2 - N4 and S2 - S4.

Instrument Intercomparison

Wolf describes the three instruments as giving acceptable agreement. The S4DWs and the waveriders are in quite close agreement for wave height and the peak wave period is in good agreement for all instruments most of the time. The bottom mounted instruments (as expected) do not always detect a high frequency peak, but are generally in close agreement validating the instrument response. The pressure recorder results for Hs show a gradual worsening in agreement with the waverider results, although other parameters remained in good agreement. Wolf discusses possible causes.


Datawell bv, Zomerlustraat 4, 2012 LM Haarlem, the Netherlands (1995).
Operation and Service Manual for "Directional Waverider" from serial no. 30109 and including 30076, 30101, 30106, 30108.

Prandle, D. (1994).
Holderness experiment - the observational programme. LOIS issue no. 2.

Wolf, J. (1996).
The Holderness Project Wave Data. Proudman Oceanographic Laboratory Internal Document No. 89.

Project Information

LOIS River-Atmosphere-Coast Study (LOIS - RACS)


The Land-Ocean Interaction Study (LOIS) was a NERC research programme designed to study processes in the coastal zone. The Rivers, Atmosphere and Coasts Study (RACS) was a major component of LOIS that looked at land-sea interactions in the coastal zone and the major exchanges (physical, chemical and biological) between rivers and estuaries and the atmosphere. The study focused on the east coast of the UK from the Wash to the Tweed.

RACS included several sub-components

RACS (A) was coordinated by the University of East Anglia and RACS (C) by the Plymouth Marine Laboratory.


The bulk of the RACS (A) data set was collected during two field campaigns in the winter (October/November) of 1994 and the summer (May/June) of 1995. During these campaigns data were collected continuously from the University of East Anglia Atmospheric Observatory at Weybourne on the north Norfolk coast. An instrumented vessel was stationed offshore to provide a second sampling site to allow changes in a given air mass to be monitored. The Imperial College Jetstream research aircraft made one flight during each campaign to provide a link between the two surface stations. The Jetstream made four additional flights in 1996 and 1997.


The coastal oceanographic survey

The coastal oceanographic data set was collected during a series of 17 RRS Challenger cruise legs. Most cruises covered two survey grids. One from Great Yarmouth to the Humber designed around the distribution of the sandbanks and a second simple zig-zag grid from the Humber to Berwick on Tweed. A large number of anchor stations, usually over one or two tidal cycles, were worked in the area of the Humber mouth or the Holderness coast.

The Humber estuarine study

The Humber estuarine data set was collected during a series of 33 campaigns on the Environment Agency vessels Sea Vigil and Water Guardian in the Humber, Trent and Ouse river systems at approximately monthly intervals between June 1993 and December 1996. Each campaign consisted of two or three one-day cruises. The tracks covered the estuary from the tidal limits of both Trent and Ouse to Spurn Point. Instrumental and sample data are available from a series of fixed stations that were sampled during every campaign.

The Tweed estuarine study

The Tweed estuarine data set was collected during a series of 13 campaigns using RV Tamaris in association with a rigid inflatable vessel at approximately monthly intervals between July 1996 and July 1997. Each campaign covered the tidal reaches of the River Tweed.

The Holderness experiment

The Holderness Experiment was designed to monitor the process of sediment transport along the Holderness coastline. It consisted of three moored instrument deployments during the winters of 1993-1994, 1994-1995 and 1995-1996. Mooring platforms were deployed at eight stations along two lines off the Holderness coast. A northerly and a southerly line of four stations each were used (N1 - N4 and S1 to S4) with the lowest numbers being inshore. Both lines were approximately perpendicular to the coast, although the S4 station lay to the south of the S line, off Spurn Head.

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1993-12-12
End Date (yyyy-mm-dd) 1993-12-17
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#637
Platform Categoryfixed benthic node

Proudman Oceanographic Laboratory Monitoring Platform Rig #637

The rig was deployed as part of the LOIS RACS study at site HMB.

Position 53° 48.05' N 0° 03.04' E
Water Depth 15.0 m
Deployed on cruise CH108C
Magnetic variation 4.0 degrees west
Mooring deployed on 12 Dec 1993 10:00
Mooring recovered on 17 Dec 1993 13:45
Period of deployment 5.2 days

Data Available

Current Meter Yes
Water Level No
Transmissometer Yes

Related Data Activity activities are detailed in Appendix 1


Cruise Name CH108C
Departure Date 1993-12-11
Arrival Date 1993-12-23
Principal Scientist(s)Geoff Millward (University of Plymouth Institute of Marine Studies)
Ship RRS Challenger

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NameHolderness Site HMB
CategoryCoastal location
Latitude53° 48.05' N
Longitude0° 3.04' E
Water depth below MSL15.0 m

LOIS RACS (Holderness Experiment) Mooring Site HMB

Site used during 1993 preliminary study period.

Position 53° 48.05' N 0° 03.04' E
Water Depth 15.0 m
Magnetic variation 4.0 degrees west

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#637

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
449706Currents -subsurface Eulerian1993-12-12 10:00:0053.8008 N, 0.0507 ERRS Challenger CH108C

Appendix 2: Holderness Site HMB

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
449706Currents -subsurface Eulerian1993-12-12 10:00:0053.8008 N, 0.0507 ERRS Challenger CH108C