Metadata Report for BODC Series Reference Number 596510
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
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Parameters |
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Problem Reports
No Problem Report Found in the Database
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.
Dr Haardt BackScat I fluorometer
The Dr Haardt BackScat I is a backscatter fluorometer designed to detect concentrations of a variety of substances in the water column. The instrument uses a Xe-flashlight source and exhibits a fast response and low power consumption. Integrated turbidity and other sensors are available and the instrument has a titanium housing rated to a maximum depth of 6000 m.
Each fluorometer is custom-built to measure substances of interest. Available spectral ranges are visible, UV I and UV II. A range of filter units are available for the measurement of chlorophyll-a, phycoerythrin, humic acids, aromatic hydrocarbons, phenol, oils, rhodamine B, sulforhodamine, fluorescein, eosin, pyranin and naphthionate.
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. |
---|---|
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). |
RV Corystes Cruise 9A/00 CTD Data Documentation
This cruise used the FSI CTD s/n 1366, for 15 stations.
Nutrients and suspended load were collected during the cruise.
STATIONS 35 - 124
(1) Thermometer data
Electronic thermometers were used on 11 occasions. The differences between pairs of thermometers were
Therm diff | N |
---|---|
0.007 | 1 |
0.009 | 3 |
0.01 | 2 |
0.012 | 4 |
0.013 | 1 |
These differences are larger than usual, as happened with Corystes 7/2000.
(2) Salinity data
Duplicate water samples were collected once , and the difference was 0.001.
(3) Sensor calibration for CTD
ALL STATIONS
(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) + 1.2
(b)Temperature
Fig.1 shows the difference between the mean thermometer and uncorrected CTD temperature on occasions, after the CTD temperatures have been corrected using the following PRT calibration coefficients. The mean difference on 11 occasions was -0.004.
The PRT temperature sensor was calibrated using the laboratory calibration coefficients from 12/5/2000
Tprt(cor) = 0.00001071*T*T + 0.00004531*T - 0.00219633
The fast thermistor temperature sensor was calibrated using the laboratory calibration coefficients from 12/5/2000
Tth(cor) = 0.00001072*T*T - 0.00035499*T + 0.00521577
(c) Salinity
Fig. 2 shows the ratio of CTD:water sample conductivity ratio after the CTD pressure and temperature sensors have been corrected using the previous coefficients. 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 = 0.657562244e-05 b = 0.163822269e-05 c = 1.0002238
rms salinity difference between water sample and corrected CTD is 0.003 for 47 data values.
Figs. 3 (a), (b), show how effectively the CTD conductivity and derived salinity has been corrected.
The histograms in fig.4 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) Fluorometer
Stations 34 and 35
Dr Haart sensor 5120 was used . The data is very variable and therefore CHL values are set to -9.
Stations 37 to 124
the SPNT fluorometer 2289 was used
linear regression calibration coefficients for
CHL = a* FLUOR.VOLTS + b
Stations 37 to 54, and 56 and 58 (range set to 0-50)
a= 11.177 b=0.0604 r**2 = 0.8321 N =53
Stations 55, 57 and 59(range set to 0-50)
a= 17.542 b=-0.0127 r**2 = 0.7807 N =23
Stations 119 (range set to 0-15)
a= 2.0958 b=0.3988 r**2 = 0.8037 N =7
Stations 124 (range set to 0-15)
a= 4.776 b=-0.0658 r**2 = 0.9116 N =8
(e) Suspended Load
the linear regression calibration coefficients were calculated using
SLOAD = a * LSS volts + b
Where:-
Station 35
a = 60.971 b = 4.8551 r**2 = 0.9782 N = 3
Stations 37-39
a = 7.2112 b = -0.8538 r**2 = 0.87 N = 12
Stations 52,53
a = 3.946 b = 0.3534 r**2 = 0.7462 N = 8
The SPNT sensor appears to fail after station 53, therefore suspended loads are set to -9.0
(F) Radi
The calibration for this cruise, (from 26/5/99 for sensor 5672), was an in-water coefficient of 0.3469 umol m-2 s-1.
Sue Norris
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 | COR9A/00 |
Departure Date | 2000-06-26 |
Arrival Date | 2000-07-11 |
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 |