Metadata Report for BODC Series Reference Number 426387

• 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

All spectra should be treated with caution.

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

InterOcean Spherical Solid State Sensor Current Meter S4DW

Manufacturer's specification: The meter (sphere, diameter 25cm) is shackled directly into the mooring cable by means of an axial titanium load bearing shaft.

Meter comprises:-

1. Electromagnetic, 2 axis current speed sensor, range 0 to 350cm/s (standard) 0 to 50 and 0 to 100cm/s (optional), resolution 0.2cm/s (standard) 0.03cm/s (0 to 50 range) 0.06cm/s (0 to 100 range), accuracy 2 per cent reading +/- 1cm/s. The sensor responds to the component of flow normal to its vertical axis.

2. Flux-gate magnetometer compass for heading information used to reference the current direction to magnetic north, compass range 360°, resolution 0.5°, accuracy 2°, tilt +/- 25° for specified accuracy.

3. Temperature stable quartz oscillator clock, accuracy 12 minutes/year.

4. Optional automatic tilt compensation i.e. the allowable tilt of the meter from the vertical at which the vertical cosine response is fully corrected, angle range +/- 45°, resolution 0.6°, accuracy (speed correction) 1 per cent (angle output) 0.25°.

5. Optional semiconductor (thermistor or platinum) temperature sensor, range -5 to +45 °C, resolution 0.05 °C, accuracy 0.2 °C, response time at 63 per cent 1 min (1.5 sec thermistor or 60msec platinum).

6. Optional conductive conductivity sensor, range 5 to 70mS/cm, resolution 0.1mS/cm, accuracy 0.2mS/cm (optional inductive sensor, range 1 to 70mS/cm).

7. Optional semiconductor strain gauge pressure sensor, range 0 to 1000dBar (70M option), resolution 1dBar (4mm with 70M option), accuracy 0.25 per cent fs.

8. Recorder, CMOS static RAM microprocessor, 64KByte (128K or 256KByte optional) performs vector averaging, burst sampling and adaptive sampling.

The S4 is a self-contained current measuring sensor enclosing all necessary solid state electronics for acquiring, processing and outputting data. Data retrieval is accomplished through a serial port without opening the instrument.

The spherical shape of the S4 is a contributing factor in the rejection of the vertical components of water movement and there are no protruding parts or sensor support structures to interfere with the water flow.

The S4 measures the magnitude and direction of the horizontal current motion of the water. Water flows through the electromagnetic field created by the instrument, thereby producing a voltage which is proportional to the magnitude of the water velocity past the sensor. This voltage is then sensed by two pairs of titanium electrodes located symmetrically on the equator of the spherical housing which forms the sensor.

The S4DW senses wave orbital current components and the 0-70 meter high-resolution depth sensor provides 4 mm depth resolution for use in wave and tide analysis. The instrument can provide for real-time measurement or internal data storage with up to 20 megabytes (7 million samples) of solid-state, non-volatile memory.

Directional Wave analysis is performed by an analysis software using the pressure and current velocity data from the S4DW instrument. The wave statistics are calculated by converting the pressure time series and orbital velocity components to the frequency domain using a Fast Fourier Transform (FFT). Once in the frequency domain the pressure amplitude data is corrected for attenuation versus frequency and depth. The direction of the waves is computed using the North and East orbital velocity vectors with auto and cross spectrum analysis of the time series.

Further details can be found in the manufacturer's specification sheet.

Definition of 2nd Harmonic of Directional Distribution Parameter

Definition

The coefficient of 2^nd harmonic of directional distribution is calculated from co-spectra of horizontal translation, corrected relative to mean direction obtained from 1^stharmonic. BODC parameters GM2C and GN2C are the parameters named respectively M2 and N2 by Kuik et al (1988). This is to distinguish them from A2 and B2, which are defined in the Datawell Manual and from the standard definitions of A2 and B2 (BODC parameters GA2C and GB2C respectively) which are not rotated relative to the mean direction.

References

Kuik, A.J.,van Vledder, G.Ph. and Holthuijsen, L.H. (1988).
A method for the routine analysis of pitch-and-roll buoy wave data. Journal of Physical Oceanography, 18, 1020-1034.

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.

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

MAFF Wave-Model Comparison

In order to validate and improve operational wave predictions from the Meteorological Office Fine Mesh Wave Model, wave measurements were made at inshore and offshore sites at three UK locations (Lyme Bay, Mablethorpe off the Lincolnshire Coast and Morecambe Bay).

BODC hold the wave measurements made at these six sites and the associated model output. The Marine Advisory Service (Commercial Services), of the Meteorological Office should be contacted regarding model output availability.

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#651

This rig was deployed as part of the LOIS RACS study at site S1.

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 S1

The site was occupied for both phase 1 (October 1994 to February 1995) and phase 2 (October 1995 to January 1996) of the Holderness Experiment by a POL Monitoring Platform (PMP) seabed mooring. This included an ADCP (zero data return in phase 1), a transmissometer, an S4 electromagnetic current meter and a pressure gauge. An EMP2000 environmental monitoring package (temperature, salinity, pH and OBS turbidity) was also fitted for the last deployment in phase 2.

The S4 and pressure gauge were programmed to sample at high frequency in burst mode, which allowed the derivation of directional wave spectra and 1-D wave spectra respectively. Basic wave statistics (H _s and T _z have been computed for all wave instruments.

The moorings were serviced several times during this period. The data returns from the instruments were as follows:

The mean sea level water depth at the station was 14m 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#651

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 S1

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.