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Metadata Report for BODC Series Reference Number 593942


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Seapoint Turbidity Meter  optical backscatter sensors
LI-COR LI-192 PAR sensor  radiometers
Unknown chlorophyll fluorometer  fluorometers
Falmouth Scientific Instruments Integrated CTD Profiler  CTD; water temperature sensor; salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) -
 

Data Identifiers

Originator's Identifier CO11/99/73
BODC Series Reference 593942
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1999-10-27 00:16
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars
 

Spatial Co-ordinates

Latitude 55.00100 N ( 55° 0.1' N )
Longitude 0.83520 W ( 0° 50.1' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 3.0 m
Maximum Sensor or Sampling Depth 67.4 m
Minimum Sensor or Sampling Height 4.6 m
Maximum Sensor or Sampling Height 69.0 m
Sea Floor Depth 72.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODERankUnitsTitle
CPHLPR011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer
FVLTWS011VoltsRaw signal (voltage) of instrument output by linear-response chlorophyll fluorometer
IRRDUV011MicroEinsteins per square metre per secondDownwelling vector irradiance as photons of electromagnetic radiation (PAR wavelengths) in the water body by cosine-collector radiometer
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALST011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
TEMPST011Degrees CelsiusTemperature of the water body by CTD or STD
TSEDBS011Milligrams per litreConcentration of suspended particulate material {SPM} per unit volume of the water body [particulate >unknown phase] by in-situ optical backscatter measurement

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database


Data Access Policy

Centre for Environment, Fisheries and Aquaculture Science (Cefas) data access conditions

The Centre for Environment, Fisheries and Aquaculture Science (Cefas) is an Executive Agency of the Department of Environment, Food and Rural Affairs (Defra), formerly the Ministry of Agriculture, Fisheries and Food (MAFF). It was also known previously as the Directorate of Fisheries Research (DFR). This data policy refers to data collected by the organisation under all titles.

  • These data have no specific confidentiality restrictions for academic users. However data are restricted for commercial requests and clearance must be obtained by BODC from Cefas before they are released.
  • 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 acknowledgement.
  • The recommended acknowledgement is: "This study uses data from the Centre for Environment, Fisheries and Aquaculture Science (Cefas), provided by the British Oceanographic Data Centre."

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.
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.
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)
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 11/99 CTD Data Documentation

This cruise used the FSI CTD s/n 1366 , for 94 stations

Nutrients and suspended load were collected during the cruise.

(1) Thermometer data

Electronic thermometers were used on 77 occasions. All the differences between pairs of thermometers were <=0.005

(2) Salinity data

Duplicate water samples were collected on 8 occasions, and samples differed as follows:-

S diff N
0.000 5
0.001 3

(3) Sensor calibration for CTD

STATIONS 2-95 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) + 0.7

(b) Temperature

Fig.1 shows the difference between the mean thermometer and uncorrected CTD temperature on 77 occasions. The mean difference was -0.005.

Fig.2 shows the differences after the CTD temperatures have been corrected using the following fast PRT calibration coefficients. 2 CTD temperatures have been deleted, as the thermometers were in good agreement, but different to the CTD temperature. The mean difference on 75 occasions was -0.005.

The new fast PRT temperature sensor was calibrated using the laboratory calibration coefficients from 1/9/1999 Tprt(cor) = 0.00001713*T*T - 0.0006972*T + 0.00504516

The fast thermistor temperature sensor was calibrated using the laboratory calibration coefficients from 1/9/1999 Tth(cor) = 0.00006284*T*T - 0.00211978*T + 0.0194287

(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. The mean salinity difference was 0.003 for 112 values.

Fig. 4 shows the ratio of CTD:water sample conductivity ratio after the CTD pressure and temperature sensors have been corrected using the previous coefficients. 4 CTD salinities have been removed, as the CTD values were varying. The mean salinity difference for 108 readings is 0.0.

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 = -0.235772621E-04

b = -0.358675245E-06

c = 1.00033737

rms salinity difference between water sample and corrected CTD is 0.003 for 108 data values.

Figs. 5 (a), (b), show how effectively the CTD conductivity and derived salinity has been corrected.

The histograms in fig.6 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 were all grouped together (since tests on grouping by area showed little difference in calibrations), to determine linear regression calibration coefficients for

CHL = a* FLUOR.VOLTS + b

where :-

a= 2.1626 b= -0.1788 r**2 = 0.8825 N = 205

(e) Suspended Load

The SPNT sensor, S/N 142, was fitted to the CTD. and the linear regression calibration coefficients were calculated using

SLOAD = a * SPNT volts + b

Where:-

a = 5.7556 b = 0.0138 r**2= 0.9697 N = 239

(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
2/12/1999

BODC image BODC image BODC image BODC image BODC image BODC image BODC image BODC image

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 COR11/99
Departure Date 1999-10-21
Arrival Date 1999-10-28
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
Q value below limit of quantification