Metadata Report for BODC Series Reference Number 578054

• 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

The instrument displayed worrying fluctuations during its calibration cast. The time series recorded during this deployment suffers from periods of constant readings (1.506 m^-1) at times of low energy such as neaps: 19/10/94, 20/10/94 and especially between 21/10/94 to 01/11/94. Beam attenuation was compared with that from CTD casts at the site (08/10/94, 09/10/94) and found to be consistently higher, by about 1 m^-1.

While the spring neap cycle is visible in the record, data from this instrument should be used with caution, as it was not performing reliably.

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: TR1762.641

Calibration

Attenuance

Calibration of raw counts into beam attenuation used the equation:

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

Where:

R is the pathlength (m) of the instrument (0.10)
BP is the blocked path counts (3)
C₀ is the count value corresponding to 5V (4760)

C₀ was determined by calibration against the CTD transmissometer on cast CP2 during cruise CH115A before deployment, and cast CP83 during CH115C at the end of the deployment.

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

Where:

A₀ = 0.048
A₁ = 0.238

Data Quality Check

The calibrated beam attenuation data were checked against the following CTD casts at station N3:

The moored transmissometer record was consistently higher than the CTD. Please read the caution document associated with this time series.

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.

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.

References

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)

Introduction

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

• BIOTA - A study of salt marshes of the Humber and Wash
• RACS (A) - An atmospheric chemistry study looking at air mass changes from the Wash into East Anglia
• RACS (C) - A study of the estuaries, coasts and coastal waters between Great Yarmouth and Berwick upon Tweed.
  1. The coastal oceangraphic survey
  2. The Humber estuarine study
  3. The Tweed estuarine study
  4. The Holderness experiment
• RACS (R) - A study of rivers that drain into the North Sea

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

RACS (A)

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.

RACS (C)

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.

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.

Data Activity or Cruise Information

Data Activity

Proudman Oceanographic Laboratory Rig#641

This rig was deployed as part of the LOIS RACS study at site N3.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

LOIS RACS (Holderness Experiment) Mooring Site N3

The site was occupied for phase 1 of the Holderness Experiment between October 1994 and February 1995 by a waverider mooring and a POL Monitoring Platform (PMP) seabed mooring. The PMP mooring included an ADCP (zero data return), a transmissometer, an S4 electromagnetic current meter and a pressure gauge. The pressure gauge was programmed to sample at high frequency in burst mode, which allowed the derivation of 1-D wave spectra. The waverider provided directional spectra. Basic wave statistics (H_s and T_z) have been computed for both wave instruments.

The moorings were serviced several times during this period and some instrument failures occurred. The data returned were as follows:

This station was not occupied for the second (1995-1996) phase of the project. One of the project trial (1993-1994) stations (HM3) was located very close to this station. The mean sea level water depth at the station was 29m and magnetic variation at the time of the deployments was 4 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:

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#641

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: Holderness Site N3

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.