Metadata Report for BODC Series Reference Number 30100

• 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 data are a mixture of observations from several sources. Many wind directions and a few wind speeds are one minute mean values taken every 3 hours (with the intervening hourly values derived by interpolation). The remaining values are 1 hour means taken at hourly intervals. The one minute means exhibit a greater variability than the hourly means.

When 3 hourly values have been used, the intervening hourly values have been formed by interpolation. This interpolation was not always linear, and may cause distortion of the data.

For several periods the wind speeds are 1 hour means while the corresponding wind directions are 1 minute means. The hourly mean speed is therefore attributed a direction which was only valid for a short period at the hour itself. Interpolation between 3 hourly values may distort more than one value.

It is possible that a measurable wind speed was recorded during the 1 hour mean, but conditions were calm on the hour when a 1 minute mean direction was recorded. The speed is therefore recorded, but with a direction set to variable or missing.

Great care is required in the use of this data set.

Data Access Policy

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Data Documentation for Boyle Station Wind Data

Instrumentation

Munro Cup Generator and Vane Anemometer deployed from ships mast to provide wind direction and speed relative to the ships heading. A compass (Plessey Magnetic Electrical Transmitting Type up to 16 January 76; Arc Industries Type DC 1298 Magnetic Electrical Transmitting Type from 17 January 76 onwards) was installed to correct direction for ships heading. Output was available on dials for direct reading, and was also continuously recorded on paper chart using a Bryans Southern Instrument Type 28000 2-channel recorder. From 20 August 74 onwards, backup recordings were made on analogue magnetic tape using a Geotech F.M. tape recorder. Several different anemometers (of the same model type) were used throughout the programme.

Calibration

All instruments: the compass and the recording system were checked by an engineer at the start of each sea trip. No calibration information is available for the anemometer; the instruments were supplied by Munro and can therefore be taken to be within specification when deployed.

Recording Methods

Two separate methods of recording wind information were operated in parallel:

1. The output of the anemometer and compass was recorded continuously on paper chart as wind speed and wind direction (in degrees magnetic).
2. One minute means of wind speed and direction were read directly from dials approximately on each hour. Direction was corrected to true North; no correction for anemometer height was applied to the wind speed. The one minute means were entered into the Meteorological Log every 3 hours, on the hours of 00, 03, 06, 09, 23, 15, 18 and 21. On occasions, hourly 1 minute means were entered into a separate log (the Oceanographic Log) or written on the paper chart records produced in (1) above.

Data Analysis

One minute means were available from the Logs for immediate use. The continuous chart record was analysed to obtain one hour means of wind speed and direction for each hour, using data from 30 minutes before to 30 minutes after the hour, and direction was corrected to true North.

When a chart observation of speed or direction was available, then it was used; otherwise a one minute mean was used. Wind speed and direction for a given observation may therefore be derived from different sources. When speed or direction values were only available from the Meteorological Log at 3 hourly intervals, hourly values were calculated by interpolation. No corrections to windspeed were applied to account for ship speed since the vessel maintained a speed of less than 2 knots whilst on station. Gust wind speed was not recorded, however, due to likely contamination by ship motion.

Wind speed was corrected to a standard height of 10 metres above sea level using the formula:

V₁₀ = V_h * (10/h) ^(1/8.5)

where:

V₁₀ = Wind velocity at 10 metres above sea level.
V_h = Wind velocity at observed height h.
h = Height of anemometer above sea level in metres.

Sources of Data

In the tabulation below:

C = Paper charts
H = Hindcast data supplied by the Meteorological Office
M = Meteorological log

Instrument History

Quality Control Procedures

Marex Quality Control

Initial quality control was performed by Marex during the initial preparation and processing of the data. Dubious values identified at this stage were deleted, or replaced by more reliable data from a backup source where available. No details of the quality control procedures applied by Marex are available.

MPS Quality Control

Additional quality control was performed by Meteorological and Plotting Services (MPS) Oceanic Limited, Bushey Heath. Records were identified in which:

1. Wind speed halved or doubled between successive records.
2. Wind direction changed by more than 100 degrees between successive records.
3. Wind speed exceeded 25 metres/second.
4. Wind direction variable with wind speed greater than 5 metres/second.
5. Wind direction missing when wind speed data were available.

A sub-set of the values identified by these tests was examined in detail, making use of the original raw data. Where the analysis was found to be erroneous, replacement values were generated from the original record. If the original record was found to be suspect, the quality control flag has been set to L.

BODC Quality Control

Two dimensional frequency distributions of wind speed versus direction were plotted and examined to ensure that all data points lay within reasonable limits. No additional numerical checking was performed by BODC. Where data are known to have originated from a 3 hourly source, any hourly values which have been computed by interpolation have been flagged T to indicate that fact.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

No Data Activity or Cruise Information held for the Series

Fixed Station Information

Fixed Station Information

Boyle Station Site History

Site

The Boyle Station (50.7° N, 007.5° W) is sited in the Celtic Sea approximately mid-way between Lands End in England and Cape Clear at the southernmost tip of Ireland, in a water depth of 107 metres. It was occupied from 24 May 1974 to 01 June 1977, initially on behalf of the Celtic Sea Oceanographic Study Group (CSOSG) and later (from mid 1975) for the Oceanographic Committee of the United Kingdom Offshore Operators Association (UKOOA). The main aim of the data collection programme was to study the environmental climate for purposes of offshore operations.

Data Collection and Processing

Data collection and processing was performed by Marine Exploration Limited (MAREX), Isle of Wight.

The data collection programme included:

1. Wave data collected at 3 hourly intervals by means of a shipborne wave recorder and a moored waverider buoy.
2. Instrumentally measured wind data collected at hourly intervals.
3. Meteorological synoptic observations made at 3 hourly intervals.
4. Current meter data collected at 10 minute intervals at three different depths.
5. Bathythermograph data collected several times a month (these data were sent to the Hydrographic Department MOD (Navy), Taunton).

The data collection programme was centred about a ship on station for periods of up to 1 month at a time. Gaps of up to a week appear in the data at the end of each on-station period. A total of 38 sea trips was made during the programme, the merchant vessel Skagerak being used throughout.

On Station History

Note: Because the waverider buoy and current meters were deployed just before the ship took station, and were recovered after the ship left station, the period covered by data from these instruments may extend up to 1 day beyond the start and end times of the on station periods given in the above table.

Related Fixed Station activities are detailed in Appendix 1

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: Boyle

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

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