Metadata Report for BODC Series Reference Number 610191
The longitude and latitude channels were flagged suspect at 03:21 31/07/1998 as the drifter may have been aboard a fishing vessel.
Centre for Environment, Fisheries and Aquaculture Science (Cefas) data access conditions
The Centre for Environment, Fisheries and Aquaculture Science (Cefas) is an Executive Agency of the Department of Environment, Food and Rural Affairs (Defra), formerly the Ministry of Agriculture, Fisheries and Food (MAFF). It was also known previously as the Directorate of Fisheries Research (DFR). This data policy refers to data collected by the organisation under all titles.
- These data have no specific confidentiality restrictions for academic users. However data are restricted for commercial requests and clearance must be obtained by BODC from Cefas before they are released.
- 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 acknowledgement.
- The recommended acknowledgement is: "This study uses data from the Centre for Environment, Fisheries and Aquaculture Science (Cefas), provided by the British Oceanographic Data Centre."
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.
Mostly taken from: Carrillo, L., 2002: Observations of cool pool jets in the continental shelf of the Celtic Sea. Ph.D. thesis, University of Wales Bangor
Twenty three satellite tracked drifting Argos buoys, manufactured by Far Horizon Marine, were deployed during cruise CO7/98 and recovered during cruise CO9A/98. These buoys have a cylindrical surface float which is connected to a holey sock drogue by relatively thin (~ 1 cm diameter) ropes. The holey sock drogue was 5.5 m long and 1.5 m diameter and centered at 30 m depth below the sea surface. These drifters were designed to have a drag area ratio of 50 which restricts wind slippage to less than 1 cms-1 for winds of 10 ms-1 (Niiler et al., 1995).
The free-drifting surface buoy was equipped with an Argos Platform Transmitter Terminal (PTT) which transmits at a frequency of 401.650 MHz +/- 4 kHz. The buoy uplink signal was received by the Argos data collection system on the NOAA polar orbiting satellites, and relayed by the System Argos in Toulhouse to a dedicated PC in the laboratory at Lowestoft (CEFAS). At 50°N each Argos PTT can be located (fixed) at least every 5-6 hours, so about 8 position fixes per day can be expected.
The Argos processing system determines the accuracy of the position calculated using the number of messages collected and the latest transmitted frequency. The accuracy of the position is represented by classes. The tables below show the accuracy of the location classes offered for one standard deviation and the probable error in velocity associated using two fixes 12 hours apart.
Standard deviation of Argos fix classes (Meldrum, 1996)
|Argos Location||East (m)||North (m)|
Error in velocity determination using two fixes 12 hours apart (Fernand, 1999)
|Argos Location||Class 1 cms-1||Class 2 cms-1||Class 3 cms-1|
Some positions are not ascertained by the Argos system. They have been given the following numerical codes at BODC.
|Argos Location||Numerical code|
|GPS fix, therefore excellent quality||10|
No Project Information held for the Series
|Principal Scientist(s)||Juan Brown (Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory)|
Complete Cruise Metadata Report is available here
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||Below detection limit|
|>||In excess of quoted value|
|A||Taxonomic flag for affinis (aff.)|
|B||Beginning of CTD Down/Up Cast|
|C||Taxonomic flag for confer (cf.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|I||Taxonomic flag for single species (sp.)|
|K||Improbable value - unknown quality control source|
|L||Improbable value - originator's quality control|
|M||Improbable value - BODC quality control|
|O||Improbable value - user quality control|
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|