Metadata Report for BODC Series Reference Number 651608
The entire fluorescence channel is suspect, with large numbers of consecutive cycles with the same value. No points have been flagged.
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."
Sea-Bird Dissolved Oxygen Sensor SBE 43 and SBE 43F
The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.
Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.
|Housing||Plastic or titanium|
0.5 mil- fast response, typical for profile applications
1 mil- slower response, typical for moored applications
|Depth rating|| |
600 m (plastic) or 7000 m (titanium)
10500 m titanium housing available on request
|Measurement range||120% of surface saturation|
|Initial accuracy||2% of saturation|
|Typical stability||0.5% per 1000 h|
Further details can be found in the manufacturer's specification sheet.
CTD Unit and Auxiliary Sensors
A Sea-Bird Electronics SBE 25 SEALOGGER CTD unit with a SBE 32 carousel water sampler was used. The CTD unit included the following sensors.
|Sensor||Manufacturer||Model||Serial number||Calibration date|
|Fluorometer||Sea Tech||Sea Tech Fluorometer||131S||1998-04-01|
|Transmissometer||Sea Tech||Sea Tech Transmissometer||238D||1996-08-02|
Sea-Bird SBE 25 SEALOGGER CTD
The SBE 25 SEALOGGER is a research-quality CTD profiling system used for coastal, estuarine and, can also be a practical option, for deep-water work. It is easily configured in the field for a wide range of auxiliary sensors. The SEALOGGER is self-powered, requires no conductive cable, and is designed for use up to 6800 meters (10,000 psia). It uses the SBE3F temperature and SBE4 conductivity sensors as well as having an external strain gauge pressure sensor. It provides pump-controlled T-C ducted flow, samples at 8 Hz, records internally and provides simultaneous real-time data via its built-in RS-232 interface.
The standard CTD unit comes with a plastic housing (rated to 600 m), although this can be replaced by aluminium housing for depths up to 6800 m.
Range: -5 to +35 °C
Accuracy: 0.002 °C
Resolution: 0.0003 °C
Range: 0 to 7 S m-1 (0 to 70 mmho cm-1)
Accuracy: 0.0003 S m-1
Resolution: 0.00004 S m-1
|Strain gauge pressure sensor|| |
Range: 0 to 20, 100, 350, 600, 1000, 2000, 3500, 7000 metres (expressed in metres of deployment depth capability)
Accuracy: 0.1% of full scale range
Resolution: 0.015% of full scale range
Options and accessories
Additional sensors can be attached to the CTD, including:
- 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 SBE 5T titanium pump can be used in place of SBE 5P pump. Further details can be found in the manufacturer's SBE 25 instrument specification.
SeaTech fluorometer S131
This fluorometer is designed to measure in situ chlorophyll-a fluorescence and provide high resolution data for assessment of phytoplankton biomass and monitoring of primary productivity in fresh or marine waters. It's versatility allows the instrument to be deployed on a mooring or in profiling mode. It is not sensitive to ambient light, permitting laboratory calibration with normal room lighting, and field measurements to be made at the water surface.
|Nominal Chl-a ranges||3, 10, 30, 100, 300 and 1000 µg L-1|
|Time constant||0.1, 1.0, 3.0 and 10 s|
|Maximum depth||3000 m|
|Excitation filter|| |
425 nm peak
200 nm FWHM*
|Emission filter|| |
685 nm peak
30 nm FWHM
*FWHM- Full-Width Half-Maximum
Further details can be found in the manufacturer's manual.
The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.
- Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
- Beam diameter: 15 mm
- Transmitted beam collimation: <3 milliradians
- Receiver acceptance angle (in water): <18 milliradians
- Light source wavelength: usually (but not exclusively) 660 nm (red light)
The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.
A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.
Further details can be found in the manufacturer's Manual.
Data were received by BODC in one ASCII format file that was subsequently split into 134 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 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|
|Fluorescence||µg l-1||In-situ fluorescence||CPHLPM01||mg m-3|
|Fluorescence||µg l-1||In-situ fluorescence with field sample calibration applied||CPHLPS01||mg m-3||Sample calibrations applied to raw fluorescence by transfer|
|Dissolved oxygen||ml l-1||Dissolved oxygen with no field calibration against sample data||DOXYSU01||µmol l-1||Conversion by transfer (ml l-1 x 44.6)|
|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 134 CTD casts was performed on FRV Clupea cruise 1204C (11 August 2004 - 30 August 2004) around Shetland, the Outer Isles and northwest Scotland. The data were collected between 07:00 hours and 20:00 hours hours during the period 13 August 2004 - 27 August 2004.
Rosette bottles were fired in order to obtain independent salinity and fluorescence measurements. The sample data were used to derive calibrations for the conductivity and fluorescence 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.
One hundred and six independent salinity samples, obtained from the CTD rosette 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 = 0.999486 and c = 0.012502.
One hundred and nine water samples obtained from the CTD rosette were also used to calibrate the CTD fluorescence data. The sample analyses yielded a straight line fluorescence calibration of the form y = mx + c, where m = 6.429 and c = -0.519093.
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)||Matt Gubbins (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|
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|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|