Metadata Report for BODC Series Reference Number 748626

• 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

IRRDUV01 and LVLTLD01: Photosynthetically Active Radiation sensor was malfunctioning data is not reliable. Increasing light irradiation with depth.

Data Access Policy

Open 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.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

RV CORYSTES: CRUISE 5/04: CTD data document

Sampling strategy

A total of 22 CTD profiles were obtained. CTD were deployed at West Gabbard and at the Warp.

For further detail refer to the cruise report.

Instrument Description

Instrumentation and data processing

The CTD used was a Falmouth Scientific Inc, serial number 1351. Samples were collected for salinity analysis (using a Guildline salinometer) to derive a calibration for the instrument conductivity sensor. A pair of digital reversing thermometers were used to compare with the CTD temperature estimates. A CHELSEA fluorometer and SEAPOINT turbidity sensor were used at all CTD stations. A LICOR photosynthetically-active- radiation sensor (with a six-decade log amplifier) was fitted to the rosette at all CTD stations. Chlorophyll samples were collected to calibrate the fluorometer and samples for suspended particulate matter analysis were used to calibrate the turbidity sensor.

A list of calibrated parameters and instrumentation used is shown below.

Change of sensors during cruise: None reported.

The data sets were calibration by CEFAS:

(a) Pressure

During the cruise the 'on deck' CTD pressure immediately prior to lowering the CTD was recorded. These 'on deck' observations have been used to correct recorded CTD pressure as follows:

P(cor) = P(unc) + dP

dp = -0.51 was used in the CTD (pressure sensor) calibration

(b) Temperature

The Platinum Resistance Thermometer (PRT) temperature sensor fitted to CTD 1366 was calibrated using PRT's during March 2004, and this was used to correct the CTD temperature :

T(cor) = T(unc) + dT

dT = a*T(unc)*T(unc) + b*T(unc) + c

where

a = -5.22e-5 b= 6.47e-4 c= -1.03e-3 for s/n 1366

(c) Conductivity

For this cruise it is assumed that the tolerance between salinity (water samples) and CTD (salinity) is accurate to 0.1 plus the manufacturer tolerance of 0.003. Most of the stations for CTD s/n 1351B, 1366B and 1397B are within the required tolerance. All CTD readings not within this tolerance have not been used for any calculations. Salinometer reading takes precedence over the CTD reading.

A least square fit was used to determine appropriate calibration coefficients:

CR(cor) = CR(ctd) [a*T(cor) + b*P(cor) + c]

where T(cor) and P(cor) are the corrected CTD temperature and pressure and

s/n 1366B

a -6.816E-05

b -2.38E-06

c 1.00116425

Using these coefficients the rms difference between water sample (salinometer) and corrected CTD salinity for s/n 1366B is 0.007 (40 values).

d) Suspended Load - Turbidity Sensor Calibration

The Seapoint turbidity sensor (s/n 1609) was calibrated by comparing recorded voltages with samples collected (during ascent of the CTD) for suspended load analysis

suspended load (mg/l) = a * Turbidity (volts) + b

where

a = 4.525E+01 b = -0.381E+01 R2 = 0.2314 (for stations 1 - 35)

e) Fluorometer - Chlorophyll Calibration

A Seapoint fluorometer (s/n 2359) was fitted to the rosette sampler and used to estimate chlorophyll levels. The sensor was calibrated by comparing recorded voltages with measured chlorophyll of samples collected in niskin bottles as the CTD rosette returned to the surface.

Chlorophyll (ug/l) = a*Fluorometer (volts) + b

a = 18.76 b = -1.848 R2 = 0.5303 (for stations 1-35)

f) Photosynthetically Active Radiation

The Licor light sensor (s/n 5672) was calibrated according to the LiCor Amplifier and Sensor calibrations which gave overall factors for calculating uE s-1 m-2.

Offset X=3.44824

L.C=0.170237

BODC post-processing and screening

Reformatting

Data for the 22 CTD casts were provided in ASCII format as .cor files. These were reformatted to the internal QXF format using a BODC transfer function, to allow the use of in-house visualisation tools. Variables within the .cor files were mapped to appropriate BODC parameter codes:

Parameters such as Specific Volume Anomaly (SVAN) and Brunt Wiesler frequency (bvf) were not transferred as they are not considered environmentally measured and can be readily reproduced from the other data.

Screening

Reformatted CTD data were visualised using the in-house editor EDSERPLO. EDSERPLO provides a graphical representation of the data so that parameters can be screened and checked for abnormalities. All parameters were plotted against pressure. Checks include identifying data spikes, gaps in the data and values that lie outside of expected limits for the environment. No data values were deleted. Flagging was achieved by modification of the associated quality control flag.

Falmouth Scientific NXIC CTD Series

The FSI NXIC CTD Series is a collection of rugged Conductivity-Temperature-Depth profilers that utilise the patented Non-eXternal Inductive Cell (NXIC) conductivity sensor, which was originally developed for the US Navy DT-705 Sound Velocity/Salinity sensor. The CTDs are fast sampling, fully integrated instruments with optional battery power, datalogging and external analog sensor input.

Models in the collection include the NXIC CT Bio Direct Read-500M, NXIC CTD Bio Direct Read-500M, NXIC CTD Bio Auto-500M, NXIC CTD Direct Read-500M, NXIC CTD Direct Read-700M, NXIC CTD Auto-500M, NXIC CTD Auto-700M, NXIC CTD-ADC with external sensors, and the NXIC ETSG Thermosalinograph. Parameters are measured to an accuracy ranging from 0.002-0.010 mS/cm for conductivity, 0.005 degC for temperature and 0.08% for full scale pressure. Now marketed by Teledyne RD Instruments.

Specifications

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

Seapoint Chlorophyll Fluorometer

The Seapoint Chlorophyll Fluorometer (SCF) is a low power instrument for in situ measurements of chlorophyll a. The SCF uses modulated blue LED lamps and a blue excitation filter to excite chlorophyll a. The fluorescent light emitted by the chlorophyll a passes through a red emission filter and is detected by a silicon photodiode. The low level signal is then processed using synchronous demodulation circuitry which generates an output voltage proportional to chlorophyll a concentration. The SCF may be operated with or without a pump.

Sensor specifications, current at August 2006, are given in the table below. More information can be found at the manufacturer's web site.

Sensor Specifications

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.

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: