Metadata Report for BODC Series Reference Number 595162
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
Data Description |
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Data Identifiers |
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Time Co-ordinates(UT) |
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Spatial Co-ordinates | |||||||||||||||||||||||||||||||||
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Parameters |
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Problem Reports
In the salinity channel there are large spikes and null values that have been flagged on the thermocline. This could be due to a mismatch between the conductivity cell and the thermistor.
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
Falmouth Scientific Integrated CTD (ICTD) Profiler
The FSI ICTD is designed to collect high precision conductivity, temperature and pressure data with self calibrating electronics. This instrument can support five primary sensors (including up to three temperature sensors) and can be coupled with a water bottle sampler. The ICTD is equipped with a titanium housing rated to 7000 m and has a sampling rate of 32 Hz.
Three temperature sensors are available: primary platinum, redundant platinum and exposed thermistor. Any combination of these can be used in the primary channels. The instrument also has multiple RS-232 serial inputs for a variety of sensors including: ADCP, Benthos PSA-916 Altimeter and WetLabs SAFire. There are an additional eight DC input channels that can support virtually any sensor that has a DC output.
Specifications:
Parameter | Conductivity | Temperature | Pressure |
Sensor | Inductive cell | Platinum thermometer | Precision-machined Silicon |
Range | 0 to 70 mS cm-1 | -2 to 35°C | Customer specified |
Accuracy | ±0.002 mS cm-1 | 0.002°C | ±0.01 % full scale |
Resolution | 0.0001 mS cm-1 | 0.00005°C | 0.0004 % full scale |
Response | 5.0 cm at 1 ms-1 | 150 ms Platinum 20 ms Thermistor* | 25 ms |
*Optional
Further details can be found in the manufacturer's specification sheet.
LI-COR LI-192 Underwater Quantum Sensor
The LI-192 Underwater Quantum Sensor is used to measure photosynthetic photon flux density and is cosine corrected. The sensor is often referred to as LI-192SA or LI-192SB (the LI-192SB model was superseded by LI-192SA). One of the main differences is that the LI-192SA model includes a built-in voltage output for interfacing with NexSens iSIC and SDL data loggers.
Sensor specifications, current at January 2012, are given in the table below. More information can be found in the manufacturer's LI-192SA andLI-192SB specification sheets.
Sensor Specifications
(Specifications apply to both models unless otherwise stated)
Absolute Calibration | ± 5 % in air traceable to NBS. |
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Sensitivity | Typically 3 µA per 1000 µmol s-1 m-2 for LI-192SB and 4 µA per 1000 µmol s-1 m-2 for LI-192SA in water. |
Linearity | Maximum deviation of 1 % up to 10,000 µmol s-1 m-2. |
Stability | < ± 2 % change over a 1 year period. |
Response Time | 10 µs. |
Temperature Dependence | ± 0.15 % per °C maximum. |
Cosine Correction | Optimized for both underwater and atmospheric use. |
Azimuth | < ± 1 % error over 360 ° at 45 ° elevation. |
Detector | High stability silicon photovoltaic detector (blue enhanced). |
Sensor Housing | Corrosion resistant metal with acrylic diffuser for both saltwater and freshwater applications. Waterproof to withstand 800 psi (5500 kPa) (560 meters). |
Seapoint Turbidity Meter
The Seapoint Turbidity Meter detects light scattered by particles suspended in water, generating an output voltage proportional to turbidity or suspended solids. Range is selected by two digital lines which can be hard wired or microprocessor controlled, thereby choosing the appropriate range and resolution for measurement of extremely clean to very turbid waters. The offset voltage is within 1 mV of zero and requires no adjustment across gains. The optical design confines the sensing volume to within 5 cm of the sensor allowing near-bottom measurements and minimizing errant reflections in restricted spaces.
Sensor specifications, current at August 2006, are given in the table below.
Sensor Specifications
Power requirements | 7 - 20 VDC, 3.5 mA avg., 6 mA pk. |
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Output | 0 - 5.0 VDC |
Output Time Constant | 0.1 sec. |
RMS Noise> | < 1 mV |
Power-up transient period | < 1 sec. |
Light Source Wavelength | 880 nm |
Sensing Distance (from windows) | < 5 cm (approx.) |
Linearity | < 2% deviation 0 - 750 FTU |
Gain | Sensitivity (mV FTU-1) | Range (FTU) | |
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Sensitivity/Range | 100x 20x 5x 1x | 200 40 10 2 | 25 125 500 ** |
** output is non-linear above 750 FTU.
Further details can be found in the manufacturer's specification sheet.
RV Corystes Cruise 5/99 CTD Data Documentation
This cruise used the FSI CTD s/n 1366, for 54 stations.
Nutrients and suspended load were collected during the cruise.
(1) Thermometer data
Electronic thermometers used on this cruise were considered unreliable due to battery failures, therefore CTD temperatures will be used.
(2) Salinity data
Duplicate water samples were collected on 13 occasions, and samples differed as follows:-
S diff | N |
---|---|
0.000 | 6 |
0.001 | 4 |
0.002 | 1 |
0.003 | 1 |
0.004 | - |
0.005 | 1 |
(3) Sensor calibration for CTD
STATIONS 1-155 CTD s/n 1366
(a) Pressure
The following calibration, obtained by using a mean of the on deck CTD readings of pressure taken during the cruise, was used to correct the pressure sensor.
P (cor) = P (unc) + 0.4
(b) Temperature
The new fast PRT temperature sensor was calibrated using the laboratory calibration coefficients from 26/5/1999
Tprt(cor) = 0.0000073*T*T - 0.0004502*T + 0.0024911
The fast thermistor temperature sensor was calibrated using the laboratory calibration coefficients from 26/5/1999
Tth(cor) = 0.0000841*T*T - 0.0023432*T + 0.015653
(c) Salinity
Fig. 1 shows the difference between the water sample salinity as measured with the salinometer and that derived from the CTD , before any calibrations have been applied to the latter's sensors. The mean salinity difference was 0.003 for 130 values.
Figs. 2 and 3 show the ratio of CTD:water sample conductivity ratio after the CTD pressure and temperature sensors have been corrected using the previous coefficients. 6 CTD salinities have been deleted because the CTD readings were variable on the thermocline. The mean salinity difference for these 124 readings is 0.002.
A set of coefficients have been derived to calibrate the CTD conductivity sensor, using a least square fit between the ratio of water sample and CTD conductivity and the CTD temperature and pressure.
CR (cor) = CR (ctd)*[a*T(cor) + b*P(cor) + c]
where a = 0.446264795E-05
b = 0.200584543E-05
c = 0.999956814
rms salinity difference between water sample and corrected CTD is 0.003 for 124 data values.
Figs. 4 (a), (b), show how effectively the CTD conductivity and derived salinity has been corrected.
The histograms in fig.5 show how well the CTD conductivity is corrected since the upper frame has been derived after the CTD temperature and pressure have been corrected, but before the CTD conductivity calibration has been applied.
If it is assumed that the salinometer is accurate to 0.006 and the CTD salinity to 0.01, then differences upto 0.016 are acceptable, and 100 % are within this when the calibration is applied.
(d) Suspended Load
The SPNT sensor, S/N 142, was fitted to the CTD. Stations were grouped by area, to determine linear regression calibration coefficients for
SLOAD = a * SPNT volts + b
Station 8 had suspended loads set to -9 because the SPNT was off range. Station 65 was not used in the calibration as the SPNT does not seem to be working correctly for the ascent profile. However, the calibration coefficients derived for stations 58-64 and station 66, will be used for station 65, as the SPNT values for the descent profile seem to fit with stations close by.
Where:-
stations 26 - 50
(stations 1-7 will use these coefficients, although not included in calculation)
a = 5.2126 b = 0.433 r**2 = 0.7473 N = 33
stations 58 - 66
a = 6.6477 b = 0.1724 r**2 = 0.7436 N = 30
stations 111 - 155
a = 4.6325 b = 0.3445 r**2 = 0.7812 N = 46
(e) Fluorometer
Stations were grouped by area, to determine linear regression calibration coefficients for
CHL = a* FLUOR.VOLTS + b
where :-
stations 26 - 50
(stations 1-8 will use these coefficients, although not included in calculation)
a= 2.3471, b= -0.0662 r**2 = 0.8271 N = 32
stations 58 - 66
a= 2.9117, b= -0.5675 r**2 = 0.824 N = 71 s
stations 111 - 155
a= 2.5225, b= -0.4145 r**2 = 0.9375 N = 53
(f) Radi
The calibration for this cruise, (from 25/1/99 for sensor 5672), was an in-water coefficient of 0.3528 umol m-2 s-1.
Sue Norris
12/8/99
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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.
Project Information
No Project Information held for the Series
Data Activity or Cruise Information
Cruise
Cruise Name | COR5/99 |
Departure Date | 1999-06-14 |
Arrival Date | 1999-07-01 |
Principal Scientist(s) | Juan Brown (Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory) |
Ship | RV Corystes |
Complete Cruise Metadata Report is available here
Fixed Station Information
No Fixed Station Information held for the Series
BODC Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
Flag | Description |
---|---|
Blank | Unqualified |
< | 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.) |
D | Thermometric depth |
E | End of CTD Down/Up Cast |
G | Non-taxonomic biological characteristic uncertainty |
H | Extrapolated value |
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 |
N | Null value |
O | Improbable value - user quality control |
P | Trace/calm |
Q | Indeterminate |
R | Replacement value |
S | Estimated value |
T | Interpolated value |
U | Uncalibrated |
W | Control value |
X | Excessive difference |
SeaDataNet Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
Flag | Description |
---|---|
0 | no quality control |
1 | good value |
2 | probably good value |
3 | probably bad value |
4 | bad value |
5 | changed value |
6 | value below detection |
7 | value in excess |
8 | interpolated value |
9 | missing value |
A | value phenomenon uncertain |
B | nominal value |
Q | value below limit of quantification |