Metadata Report for BODC Series Reference Number 762411

• 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

No Problem Report Found in the Database

Data Access Policy

SIMORC data access conditions

The data collated and held at BODC on behalf of the SIMORC project are restricted. However, the data will be available to download from the Official SIMORC Website, as part of the project protocol. The data set will initially include data from the oil companies TOTAL, Shell and BP.

Narrative Documents

Teledyne RDI's Workhorse Long Ranger ADCP

The Workhorse Long-Ranger acoustic doppler current profiler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented broadband signal (75 kHz) and a standard depth rating of 1500m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

The instrument comprises:

• An aluminium transducer head with four beams at 20^o from the vertical in a convex configuration, temperature sensor, electronic assemblies, fluxgate compass, pitch and roll sensors
• 4 x 28 D-cell alkaline battery packs
• 40 MB PC card internal memory (upgradeable to 440 MB)
• 1500m depth rated 6061 aluminium pressure case. End cap with wet material connector and dummy plug

BODC Current Meter Screening

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:
  • Depths of meter and sea bed.
  • Times for mooring deployment and for start/end of data series.
  • Length of record or number of data cycles, the cycle interval, the clock error and the period over which accrued.
  • Parameters stated as measured 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 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 following types of irregularity, each relying on visual detection in the time series 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, deemed abnormal, then instead of flagging the individual suspect values, a caution may be documented. Likewise documents will highlight irregularities seen in the current vector scatter plots such as incongruous centre holes, evidence of mooring 'knock-down', abnormal asymmetry in tidally dominated records or gaps as when a range of speeds or directions go unregistered due to meter malfunction.

The term 'knock-down' refers to the situation when the 'drag' exerted on a mooring at high current speeds may cause instruments to tilt beyond the angle at which they are intended to operate. At this point the efficiency of the current sensors to accurately record the flow is reduced.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought, and where necessary, documented. This covers inconsistencies in the following:

• Maximum and minimum values of parameters (spikes excluded).
• The orientation and symmetry of the current vector scatter plot.
• The direction of rotation of the current vectors.
• The approximate amplitude and periodicity of the tidal currents.
• The occurrence of meteorological events and, finally, for series for which no time check was possible, the phase.

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.

BODC Processing

Data were received in ASCII format files. These series were reformatted to the internal QXF format using BODC transfer function 415. The following table shows how the variables within the file were mapped to the appropriate BODC parameter codes:

Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO. Any data considered as suspect were flagged 'M'.

Nigeria Usan ADCP processing

The originator reported the following processing notes:

Data were transferred to the Fugro GEOS Alpha server for quality control, processing and analysis. Quality control procedures applied during post-processing included, but were not limited to the following:

• Production of quality control plots to assess the general quality of the data and evaluate the effectiveness of each individual quality control procedure.
• Error flagging of records with current speeds beyond extreme limits and exceeding quality control parameter thresholds carried out on all data from all measurement depths.
• Application of the magnetic declination of -3.3° E.
• Inspection of the quality of current, wave, water level, temperature and salinity data by an experienced oceanographer to identify and remove any remaining anomalous values.

There was some evidence of biological interference in the ADCP current velocity data from both the Workhorse and Long Ranger instruments, which was removed from the final data sets by manual editing. The biological interference was identified in the vertical velocity and echo amplitude records from the instruments. Elevated values of these parameters corresponded to dawn and dusk migrations of zooplankton. Whilst care has been taken to remove all such erroneous data, it is possible that other data records remain which have been influenced in some way by acoustic scatterer movement.

Project Information

System of Industry Metocean data for the Offshore and Research Communities (SIMORC)

The EU-funded SIMORC project is a collaborative effort between MARIS (Netherlands), BODC (UK), the International Association of Oil and Gas Producers (OGP) and IOC-IODE to provide a harmonised and quality controlled metocean data set from data collected by oil and gas producers, accessible through the SIMORC protocol.

Data Activity or Cruise Information

Data Activity

SIMORC Moored Instrument OPL222#1

The generic position of this site is 03° 30.229' N, 007° 29.683' E with a water depth of 743 m.

3 moorings consisting of 2 ADCP, 1 current meter and 1 water level recorder were deployed from a subsurface mooring.

This particular mooring was deployed on 30/05/2004 and was removed on 04/09/2004. This current mooring was set on behalf of TOTAL in Nigeria, OPL 222 Usan and consisted of the following series.

Related Data Activity activities are detailed in Appendix 1

Fixed Station Information

Fixed Station Information

Nigeria OPL 222 Usan Fixed Station Document

On behalf of Elf Petroleum Nigeria Ltd, Fugro Global Environmental and Oceanographic Sciences has undertaken a one-year program of deep water oceanographic measurements in Block OPL222.

A single mooring was deployed, comprising oceanographic instrumentation measuring current speed and direction data throughout the water column, wave height and period, water level elevation and seawater temperature data.

A CTD profiler was deployed and recovered prior to both the mooring deployment and recovery to measure temperature and salinity profiles throughout the water column and verify the water depth.

The moorings deployed lie within a box bounded by co-ordinates 3.300715° N, 7.00628° E at the southwest corner and 3.60702° N, 7.52° E at the northeast corner.

Meteocean data have been collected on behalf of Total from the OPL 222 Usan Station as follows:

21 CTD casts were taken from 21/06/2004 to 04/07/2004.

Where

• ADCP = Acoustic Doppler Current Profiler
• CM = Current Meter
• CTD = Pressure, temperature and conductivity profiler
• WLR = Water Level Recorder

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: OPL222#1

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: Nigeria OPL 222 Usan

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.