Metadata Report for BODC Series Reference Number 1812161

• 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 Quality Report for Wave data from TRIAXYS directional wave buoy at Site B in the Bristol Channel

The originator flagged the first 17 cycles of the GTPKZZ01 channel as invalid data due to the instrument being out of the water. These flags were converted to BODC flags during processing and all other channels were also flagged 'L' for these cycles as the same reason applies. The remaining data were screening using in house visualisation software were any obvious outliers and spikes were looked at in closer detail and flagged if necessary.

GTPKZZ01

There are a number of cycles in this channel where GTPKZZ01 drops to 0 s. Where this occurs the values before and after the period are significantly higher and other channels are null. These cycles have been flagged suspect during BODC processing.

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

TRIAXYS Directional Wave Buoy

The TRIAXYS Directional Wave Buoy uses the TRIAXYS Next Wave II Sensor for continuous wave sampling and accurate wave data.

Specifications

For more information about this model see the manufactures TRIAXYS manual.

BODC Processing of TRIAXYS Directional Wave Buoy Moorings in the Bristol Channel

Data Processing

Data were received in Excel spreadsheets accompanied by a number of metadata reports in pdf format and following BODC procedures, the data and reports were subsequently archived. During archiving, the Excel spreadsheets were also saved in csv format. The data contained wave and current data with varying temporal coverage from two TRIAXYS directional wave buoy moorings in the Bristol Channel. In addition to the current data, sea surface temperature was also included in the data. The csv files were transferred to BODC internal format using standard BODC processing procedures.

The variables provided in the files were mapped to BODC parameter codes as follows:

Wave parameters

Current parameters

Screening

Post transfer analysis and crosschecks were applied according to BODC procedures. This involved the screening of data using BODC's in house visualisation software where any suspect data were flagged but not removed. During processing, any data that were flagged as suspect by the originator were converted to BODC data flags.

Originator's Processing of Moorings in the Bristol Channel

Data Acquisition and Analysis

A number of moorings were deployed in the Bristol Channel between March 2010 and April 2011 by GEMS Survey Ltd who were contracted to collect metocean data for the environmental impact assessment of a proposed offshore wind farm. Moorings were deployed at three sites (A, B and D) with a Waverider buoy deployed on the mooring at site A and Acoustic Wave and Current (AWAC) profilers deployed at sites B and D along with water quality sondes.

During the AWAC moorings, the instruments were recovered and returned to shore for servicing, including the downloading of data, before being redeployed. However, after the first deployment of AWAC D on 10 MAR 2010, the frame containing the AWAC could not be located due to a fault with the floatation module. This was also the case when trying to recover AWAC B for the second time when recovery attempts of the AWAC on 12 JUN 2010 were unsuccesful. In order to continue collecting data, a second mooring was deployed at sites B and D consisting of a TRIAXYS directional wave buoy fitted with Nortek Aquadopp current profiler. A further mooring was also deployed at site B containing two YSI 6000 sondes.

The Waverider buoy was also recovered for servicing but during the first service visit, it was not possible to locate the Waverider. The buoy was found three weeks later during a cruise for a different project after which it was transported back to the laboratory where the data were downloaded and the Waverider serviced. A replacement Waverider buoy was later deployed at site A. Basic data, including a GPS position, were transmitted to the GEMS' office every 30 minutes but during subsequent service visits the full dataset was downloaded. If the buoy was noted to be drifting on the current, the buoy was recovered, serviced, data downloaded and redeployed. When the buoy was drifting, this was found to be due to the bungee cord being cut.

Data Quality

The lost AWAC B frame was located and recovered using a Remotely Operated Vehicle (ROV) but during this process the AWAC was inverted and so no valid data were collected. In addition to this loss of data, the water quality sonde data were not deemed to pass GEMS QC and so were rejected. This was also the case for the water quality sonde data at site D as the turbidity sensor failed. Again, the data were rejected.

A member of the public found the floatation module that failed on the AWAC D mooring and returned it to GEMS who were able to download the data logged by the unit. During QC it was found that the battery had started to deplete and so any data collected after this point were rejected.

There were also issues with the TRIAXYS B mooring as during QC it was found that the memory card was corrupted and there were no logged data available. Real-time data were then instead used for analysis. During the QC of the real-time data, values that were greater than 20 s in the peak wave period channel (BODC parameter code GTPKZZ01) were removed as the values were a result of the post processing software.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

TRIAXYS Directional Buoy Mooring at Site B

The deployed mooring consisted of a TRIAXYS Directional Wave Buoy (surface buoy) with LED flash light and Iridium satellite antenna; 15m bungee cord with backup rope; 60m rope for the mooring with a 20kg float at the mid point; 4m galvanised chain and 500kg chain ballast. There was also a Nortek Aquadopp current profiler onboard the buoy. The TRIAXYS wave buoy was configured to record wave data for 20 minutes every 30 minutes. Current data were also recorded at 30 minute intervals. The buoy sent basic wave and current telemetry every 30 minutes to the GEMS offices via the Iridium satellite system with the complete data set being downloaded at service/recovery visits. Two TRIAXYS directional wave buoys were used during the duration of the mooring which were deployed and recovered by the MV Boy Brendan.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Moorings in the Bristol Channel: Fixed Station, Site B

GEMS Surveys Limited were contracted to complete metocean data collection in the Bristol Channel by deploying a number of moorings as part of the Atlantic Array wind farm development project. Three moorings were deployed at site B between March 2010 and April 2011.

The first mooring collected acoustic wave and current profiler (AWAC) and water quality parameter data over a six week period - beyond the six weeks issues occurred with recovering the mooring. The water quality parameters included temperature, conductivity, salinity, dissolved oxygen and pH. Wave data were collected every 60 minutes and current data every 20 minutes.

The second mooring, consisting of a TRIAXYS directional wave buoy fitted with a Nortek Aquadopp current profiler, was deployed when the first mooring could not be recovered. The TRIAXYS buoy sent basic wave and current telemetry every 30 minutes to the GEMS office via the Iridium satellite system with the complete data set downloaded at service/recovery visits. In the complete dataset, wave data were recorded for 20 minutes every 30 minutes and current data were recorded at 30 minute intervals in 50 x 1m bins.

A final mooring was also deployed at site B containing two YSI 6000 sondes. The sondes were measuring near bed turbidity and sampled every 20 minutes.

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: TRIAXYS_B

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: Site B

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.