Metadata Report for BODC Series Reference Number 653210
Fluorescence values are very low, probably as a result of incorrect settings. The entire channel should be treated as suspect.
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. 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.
Seapoint Chlorophyll Fluorometer
The Seapoint Chlorophyll Fluorometer (SCF) is a low power instrument for in situ measurements of chlorophyll a. The SCF uses modulated blue LED lamps and a blue excitation filter to excite chlorophyll a. The fluorescent light emitted by the chlorophyll a passes through a red emission filter and is detected by a silicon photodiode. The low level signal is then processed using synchronous demodulation circuitry which generates an output voltage proportional to chlorophyll a concentration. The SCF may be operated with or without a pump.
Sensor specifications, current at August 2006, are given in the table below. More information can be found at the manufacturer's web site.
|Power requirements||8 - 20 VDC, 15 mA avg., 27 mA pk.|
|Output||0 - 5.0 VDC|
|Output Time Constant||0.1 sec.|
|Power-up transient period||< 1 sec.|
|Excitation Wavelength||470 nm CWL, 30 nm FWHM|
|Emission Wavelength||685 nm CWL, 30 nm FWHM|
|Sensing Volume||340 mm3|
|Minimum Detectable Level||0.02 µg l-1|
|Gain||Sensitivity, V µg-1 l-1||Range, µg l-1|
WETLabs C-Star transmissometer
This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.
Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.
This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.
|Pathlength||10 or 25 cm|
|Wavelength||370, 470, 530 or 660 nm|
~ 20 nm for wavelengths of 470, 530 and 660 nm
~ 10 to 12 nm for a wavelength of 370 nm
|Temperature error||0.02 % full scale °C-1|
|Temperature range||0 to 30°C|
|Rated depth|| |
600 m (plastic housing)
6000 m (aluminum housing)
Data were received by BODC in one ASCII format file that was subsequently split into 25 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 the 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||CNDCST01||S m-1||Conversion by transfer (mS cm-1 x 0.1)|
|Salinity||Salinity of the water column||PSALST01||Dimensionless||Derived by transfer using UNESCO 1983 algorithm|
|Fluorescence||µg l-1||In-situ fluorescence||CPHLPM01||mg m-3|
|Beam attenuation||m-1||Attenuance of the water column||ATTNMR01||m-1|
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 25 CTD casts was performed on FRV Clupea cruise 1504C (08 October 2004 - 22 October 2004) around northwest Scotland. The data were collected between 09:00 hours and 19:00 hours hours during the period 10 October 2004 - 19 October 2004.
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.
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)||James A M Kinnear (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|