Metadata Report for BODC Series Reference Number 656508
No Problem Report Found in the Database
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."
CTD Unit and Auxiliary Sensors
A Sea-Bird Electronics SBE 19 SEACAT CTD unit was used. Water samples were collected with a 1.7 litre Knudsen reversing water bottle, which was attached to the CTD frame and closed with a messenger. The CTD unit included the following sensors.
|Sensor||Manufacturer||Model||Serial number||Calibration date|
Sea-Bird SBE 19 and SBE 19plus SEACAT Profiler CTDs
The SBE 19 SEACAT Profiler is a self-contained, battery powered, pumped CTD system designed to measure conductivity, temperature, and pressure in marine or fresh water environments to depths of 10,500 meters. It was replaced by the SBE 19plus model in 2001. An updated version of this instrument is the SBE 19plus V2, which incorporates an electronics upgrade and additional features, with six differentially amplified A/D input channels, one RS-232 data input channel, and 64 MB FLASH memory.
The standard CTD unit comes with a plastic housing (rated to 600 m), although this can be replaced by titanium housing for depths up to 7000 m. It is typically used for CTD profiling although a conversion kit is available for mooring deployments. The CTD can also be attached to an SBE 36 CTD Deck Unit and Power/Data Interface Module (PDIM) for real-time operation on single-core armored cable up to 10,000 m.
|Parameter||SBE 19||SBE 19plus|
Range: -5 to +35 °C
Accuracy: 0.01 °C
Resolution: 0.001 °C
Calibration: +1 to +32 °C*
Range: -5 to +35 °C
Accuracy: 0.005 °C
Resolution: 0.0001 °C
Calibration: +1 to +32 °C*
Range: 0 to 7 S m-1 (0 to 70 mmho cm-1)
Accuracy: 0.001 S m-1
Resolution: 0.0001 S m-1
Calibration: 0 to 7 S m-1. Physical calibration over the range 1.4 - 6 S m-1*
Range: 0 to 9 Sm-1
Resolution: 0.00005 (most oceanic waters, resolves 0.4 ppm in salinity); 0.00007 (high salinity waters, resolves 0.4 ppm in salinity); 0.00001 (fresh waters, resolves 0.1 ppm in salinity)
Calibration: 0 to 9 S m-1. Physical calibration over the range 1.4 - 6 S m-1*
|Strain gauge pressure sensor|| |
Range: 0 to100, 150, 300, 500, 1000, 1500, 3000, 5000, 10000 or 15000 psia
Accuracy: 0.25% of full scale range (100 - 1500 psia); 0.15% of full scale range (3000 - 15000 psia)
Resolution: 0.015% of full scale
Calibration: 0 to full scale in 20% steps
Range: 0 to 20, 100, 350, 1000, 2000, 3500 or 7000 m
Accuracy: 0.1% of full scale range
Resolution: 0.002% of full scale range
Calibration: ambient pressure to full scale range in 5 steps
*Measurements outside this range may be at slightly reduced accuracy due to extrapolation errors.
Options and accessories
Additional sensors can be attached to the CTD, including:
- high accuracy Paroscientific Digiquartz pressure sensor (depth range 0 to 20, 60, 130, 200, 270, 680, 1400, 2000, 4200, 7000 or 10500 m; accuracy 0.02% of full scale; resolution 0.0025% of full scale)
- Dissolved Oxygen (SBE 43 DO Sensor)
- pH* (SBE 18 pH Sensor or SBE 27 pH/ORP Sensor)
- radiance (PAR)
- light transmission
- optical backscatter (turbidity)
The standard SBE 5M pump may be replaced by an SBE 5P (plastic housing) or 5T (titanium housing) pump for use with dissolved oxygen and/or other pumped sensors. Further details can be found in the manufacturer's SBE 19plus V2 instrument specification or theSBE 19 andSBE 19 plus user guides.
Data were received by BODC in one ASCII format file that was subsequently split into 27 separate files, one for each CTD profile. The series were reformatted to the internal QXF format using BODC transfer function 340. Sample calibrations were applied to the conductivity and fluorescence data. The following table details mapping of variables to BODC parameter codes.
|Original parameter name||Original Units||Description||BODC Parameter Code||BODC Units||Comments|
|Pressure||Decibars||Pressure exerted by the water column||PRESPR01||Decibars|
|Temperature||°C||Temperature of the water column||TEMPST01||°C|
|Conductivity||mS cm-1||Electrical conductivity of the water column calibrated against independent measurements||CNCLCCI1||S m-1||Conversion by transfer (mS cm-1 x 0.1). Sample calibrations applied by transfer.|
|Salinity||Salinity of the water column||PSALST01||Dimensionless||Derived by transfer using UNESCO 1983 algorithm|
Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO. Any data considered as suspect were flagged 'M'. Flags from the originator marking suspect data were retained during transfer and flagged 'L'.
Originator's Data Processing
A total of 27 CTD casts was performed on FRV Scotia cruise 1504S (21 October 2004 - 07 November 2004) between Shetland and Norway. The data were collected during day and night over the period 22 October 2004 - 03 November 2004.
Water samples were collected in order to obtain independent salinity measurements. The sample data were used to derive calibrations for the conductivity data collected by the CTD.
The raw CTD data files were processed through the SeaBird Electronics SeaSoft data processing software following standard procedures. The originators used in-house interactive visual display editing software to edit out individual spikes in the primary temperature and conductivity channels. In addition, a low-pass filter (Sy 1985) was applied to particularly noisy data. An ASCII file was generated for each CTD cast and all files from a cruise were concatenated into one ASCII file which was submitted to BODC.
Sy A., 1985. An alternative editing technique for oceanographic data. Deep Sea Research Part A: Oceanographic Research Papers, 32 (12), 1591-1599.
Twenty five independent salinity samples, obtained from the water sampler throughout the cruise, were used to calibrate the CTD conductivity data. Outlying points were discarded and the sample analyses yielded a straight line conductivity calibration of the form y = mx + c, where m = 1.002144 and c = -0.130582.
The uncalibrated data and calibrations were submitted to BODC, who applied the appropriate corrections.
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.
No Project Information held for the Series
|Principal Scientist(s)||Paul G Fernandes (Fisheries Research Services Aberdeen Marine 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|