Metadata Report for BODC Series Reference Number 546758
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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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
Guildline 8705 CTD
The 8705 CTD is a conductivity-temperature-pressure profiler designed for marine applications down to depths of 6000 m. The instrument includes an anodised aluminium tube with a steel cage to protect the temperature and conductivity sensors and a urethane cap to protect the pressure sensor.
Specifications
Parameter | Range | Accuracy | Resolution | Stability | Response time |
---|---|---|---|---|---|
Pressure | 0 to 6000 dbar | ± 0.15% of full range | ± 0.01% of full range | - | < 50 ms |
Temperature | -2 to 30 °C | ± 0.005 °C | ± 0.0005 °C | ± 0.002 °C over 30 days ± 0.0025°C over 6 months | < 50 ms |
Conductivity * | 100 ppm to 40 ppt | ± 0.005 ppt | ± 0.001 ppt | ± 0.002 ppt over 6 months | < 50 ms |
* Conductivity specifications are given in terms of equivalent salinity
Further details can be found in the manufacturer's specification sheet.
RV Corystes 5A/1993 (JONUS Exercise 16) CTD Data Documentation
Introduction
For this cruise, the Guildline CTD (s/n 45056) was used. The following is a presentation of the data returned from all stations (stations 2 to 132).
Data Collection
Fifty-nine CTD profiles were obtained on this cruise; reversing thermometers were used to measure water temperature and samples were collected for salinity analysis.
Left and right hand thermometer readings were available on most stations (total 58 pairs). Initially, six pairs of thermometer results were not used because the differences between them were >0.025 °C.
All the thermometers were graduated at 0.02 °C intervals and a comparison of the differences follows:
Difference °C | No. | Cumulative % |
---|---|---|
0.00 - 0.01 | 25 | 48 |
0.01 - 0.02 | 21 | 88 |
0.02 - 0.03 | 6 | 100 |
Water samples were collected on all stations for analysis with a Guildline salinometer. Duplicate samples were taken on only one station.
Sensor Calibration for Guildline CTD
Pressure
The laboratory calibration of March 1992 with the sensor at 6 °C was used to correct the pressure sensor:
P(cor) = P(ctd) - 1.6db
Temperature
Fig. 1 shows the differences between the (mean) thermometer and uncorrected CTD temperature when the left/right thermometer differences were <0.03 °C (52 occasions). The mean difference calculated for these was 0.017 °C.
This compares with the laboratory calibration of February 1993 which estimated the CTD correction to be approximately 0.009 °C at the temperatures encountered on this cruise. The sensor was corrected using the laboratory calibration coefficients:
T(cor) = T(ctd) + dT
where:
dT = a*T(ctd)*T(ctd) + b*T(ctd) + c
a = 1.21101E-05
b = 5.92251E-04
c = 3.18442E-03
Further examination of the data led to the removal of a further eleven CTD or thermometer pairs and Fig. 2 shows the differences between these remaining 41 pairs of good thermometer and CTD data after the latter have been corrected. The mean difference is 0.001 °C and all the differences lie within 0.03 °C, supporting the belief that if the thermometers are accurate to 0.02 °C then the CTD temperatures are accurate to 0.01 °C. Ten differences are outside ±0.012 °C.
Salinity
Fig. 3 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. Note that 6 data values have been removed prior to plotting Fig. 3 because the differences were large, suggesting either an erroneous CTD value or water sample salinity. The plot in Fig. 3 suggests that the CTD has a tendency to over-estimate salinity.
Fig. 4 shows the ratio of CTD:water sample conductivity ratio after the CTD pressure and temperature sensors have been corrected using the coefficients for temperature and pressure above.
For these data, 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:
T(cor) and P(cor) are the corrected CTD temperature and pressure respectively
a = 0.154477980E-04
b = 0.197859277E-05
c = 0.999379414E+00
RMS salinity difference between water sample and corrected CTD = 0.011 and the number of data values = 102.
Fig. 5 illustrates how effectively the CTD conductivity and derived salinity have been corrected. The tendency of the CTD to over-estimate salinity has been removed.
The histograms in Fig. 6 show how well the CTD conductivity is corrected since the upper one 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 0.003 and the CTD salinity to 0.01, then differences between ±0.013 are acceptable. Some 78% of the values lie within this range after the calibrations have been applied.
Transmission and Suspended Load
Because of a fault in the equipment, no transmission data were logged during the whole of this cruise. Full scale voltages were recorded throughout. Consequently, no calibration of this sensor is possible.
Stuart Jones
October 1993
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
Joint Nutrient Study I (JoNuS)
Concerns by the scientific community about the impact of nutrient inputs to the sea; a lack of information on inputs from the UK and on the spatial and temporal distribution and cycling of nutrients in UK waters provided the impetus for the JoNuS project.
The project sought to quantify the input of nitrogen, phosphorus and silicon from UK estuaries to the North Sea through a good understanding of the estuarine processes that control the flow of these nutrients. It focussed on the Great Ouse/Wash and the Humber outflows. Its specific objectives were:
- To measure the fluxes of nutrient elements (N, P, Si) through selected major estuaries on a quantitative annual basis in order to determine the net input to the sea resulting from gross river inputs.
- To quantify the processes controlling the fluxes of nutrients through estuaries.
The Centre for Environment, Fisheries and Aquaculture Science (CEFAS) hosted the project, which involved scientists from CEFAS, the University of East Anglia, the University of Essex, the Plymouth Marine Laboratory and the National Rivers Authority (now the Environment Agency). It was funded by the then Ministry of Agriculture, Fisheries and Food (MAFF) and the Department of Environment, now the Department of Environment, Food and Rural Affairs (Defra).
The project ran from April 1990 to March 1995, with marine field data collection between May 1990 and December 1993. Data collection involved ship based surveys which were complemented by estuarine transects and specific process studies.
Initially, the surveys were on a quarterly basis up to October 1992, however monthly surveys were carried out during 1993. During this intensive survey period, the programme focused on the Great Ouse/Wash; with a continuing, but lower level, of activity devoted to the Humber. An additional multi-project cruise, carried out in January 1995, also complemented the JoNuS data set. Further details of the JoNuS I cruises are provided below:
Cruise identifier | Date | Comments |
---|---|---|
RV Cirolana CIR5/90 | 1990-05-03 - 1990-05-20 | None |
RV Cirolana CIR7/90 | 1990-07-06 - 1990-07-25 | None |
RV Cirolana CIR10/90 | 1990-10-29 - 1990-11-16 | None |
Seeker 2/90 | 1990-10-29 - 1990-11-03 | Sediment and water sample collection only |
RV Cirolana CIR1/91 | 1991-01-05 - 1991-01-23 | None |
RV Cirolana CIR4/91 | 1991-04-12 - 1991-05-02 | None |
RV Cirolana CIR8A/91 | 1991-09-25 - 1991-10-09 | None |
RV Corystes (88-04) COR1/92 | 1992-01-03 - 1992-01-20 | None |
RV Corystes (88-04) COR3A/92 | 1992-02-14 - 1992-02-26 | None |
RV Cirolana CIR8/92 | 1992-07-29 - 1992-08-06 | None |
RV Corystes (88-04) COR11/92 | 1992-09-28 - 1992-10-12 | None |
RV Cirolana CIR1/93 | 1993-01-08 - 1993-01-22 | None |
RV Corystes (88-04) COR2A/93 | 1993-02-03 - 1993-02-07 | None |
RV Corystes (88-04) COR2C/93 | 1993-02-18 - 1993-02-24 | None |
RV Corystes (88-04) COR5A/93 | 1993-05-04 - 1993-05-10 | None |
RV Corystes (88-04) COR6A/93 | 1993-06-08 - 1993-06-14 | None |
RV Cirolana CIR7B/93 | 1993-07-26 - 1993-08-02 | None |
RV Corystes (88-04) COR9/93 | 1993-08-20 - 1993-08-26 | None |
RV Cirolana CIR9B/93 | 1993-09-30 - 1993-10-11 | None |
RV Corystes (88-04) COR13/93 | 1993-12-15 - 1993-12-21 | None |
RV Cirolana CIR1/95 | 1995-01-06 - 1995-01-31 | None |
Data Activity or Cruise Information
Cruise
Cruise Name | COR5A/93 |
Departure Date | 1993-05-04 |
Arrival Date | 1993-05-10 |
Principal Scientist(s) | Juan Brown (Ministry of Agriculture, Fisheries and Food Lowestoft Fisheries 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 |