Metadata Report for BODC Series Reference Number 638458

• 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

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:

*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 The sensor is often referred to as LI-192SA or LI-192SB (the LI-192SB model was superseded by LI-192SA).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)

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

** output is non-linear above 750 FTU.

Further details can be found in the manufacturer's specification sheet.

RV Corystes Cruise 01/00 CTD Data Documentation

This cruise used the FSI CTD s/n 1366 , for 70 stations

Nutrients and suspended load were collected during the cruise.

(1) Thermometer data

Electronic thermometers were used on 65 occasions. All the differences between pairs of thermometers were <=0.005

(2) Salinity data

Duplicate water samples were collected on 4 occasions, and samples differed as follows:-

(3) Sensor calibration for CTD

STATIONS 3-119 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 63 occasions. The CTD hit bottom at station 31, therefore the CTD value was deleted. At station 43 there was a probable error in reading both thermometers, therefore their results were deleted. The mean difference was -0.008.

Fig.2 shows the differences after the CTD temperatures have been corrected using the following fast PRT calibration coefficients. The mean difference on 63 occasions was -0.009.

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

All water samples for stations 3 to 16 were deleted due to a problem with the portasal analyser. One duplicate water sample was deleted at station 79 bottom as it differed from the CTD salinity and other water sample.

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.

5 CTD salinities were deleted from stations 73,74,75 and 78 due to a large salinity difference, which may be due to these stations being close to Holland. The mean salinity difference was 0.005 for 163 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. The mean salinity difference for 163 readings is 0.007.

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 = -0.303603628E-04 b = -0.342952469E-06 c = 1.0003808

rms salinity difference between water sample and corrected CTD is 0.003 for 163 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 98 % are within this when the calibration is applied.

(d) Fluorometer

linear regression calibration coefficients for

CHL = a* FLUOR.VOLTS + b

where :-

Stations 73 to 80 (Off Holland)

a= 0.3311 b= 0.0196 r**2 = 0.7373 N = 67

Stations 3 to 49, 62 to 71, 81 to 86 and 109 to 119 (Central)

a= 0.7188 b= -0.0241 r**2 = 0.6853 N = 310

Stations 50 to 55, 87to 108 (Nearest Shore)

a= 1.4232 b= -0.2611 r**2 = 0.8434 N = 111

(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:-

Stations 50 to 55

a = 92.524 b =4.1332 r**2 =0.9929 N = 11

Station 3 only

a=5.1357 b=0.0 r**2 = 0.5049 N=3

All other stations

a = 99.048 b = 1.5849 r**2 = 0.9286 N = 159

(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
24/2/2000

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

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: