Metadata Report for BODC Series Reference Number 808705
No Problem Report Found in the Database
RAPID Cruise D279 Underway Surface Hydrography Data Quality Report
Salinity and Temperature
The start of the series is flagged suspect on 04 April until 18:45 for temperature and 19:51 for salinity.
There is a steady increase in beam attenuation throughout the cruise, possibly indicating sensor fouling. There are numerous spikes throughout the series, which have been flagged suspect.
There is a step in the data at 19:49 on the 04/04/2004 with values around 0.14 volts before and 0.08 volts afterwards. The higher values (at the start of the cruise) have been left unflagged, but should be used with caution.
Open Data supplied by Natural Environment Research Council (NERC)
You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."
Falmouth Scientific Inc. OEM CT sensor
The OEM CT sensor is designed to provide high accuracy conductivity and temperature measurements in a package that can be readily integrated into user systems. The CT sensor relies on an inductively coupled conductivity sensor, with a large inside diameter that eliminates the need for pumps. A high grade Platinum Resistance Thermometer is used to measure temperature.
Sensor specifications are given in the table below. Since 2009 this instrument has been manufactured by Teledyne RD Instruments as a Citadel CT-EK Sensor. More information about the instrument can be found on the Teledyne Citadel specification sheet.
|Instrument Parameter||Small CT Cell Conductivity||Large CT Cell Conductivity||Temperature|
|Range||0 to 70 mS cm-1||0 to 70 mS cm-1||-2 to 35 degrees C|
|Accuracy||±0.020 mS cm-1||±0.010 mS cm-1||±0.050 degrees C|
|Stability||±0.005 mS cm-1 mo-1||±0.003 mS cm-1||±0.005 degrees C mo-1|
|Response||20 cm @ 1 m s-1||15 cm @ 1 m s-1||20 seconds internal, 1 second external|
|Power Input||50 mW @ 6 VDC, voltage range 6 - 14 VDC|
|Logic||2 0 - 5 VDC control lines|
|Output Impedance||500 ohms|
WET Labs WETStar Fluorometers
WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.
|Chlorophyll WETStar||CDOM WETStar||Uranine WETStar||Rhodamine WETStar||Phycoerythrin WETStar|
|Excitation wavelength||460 nm||370 nm||485 nm||470 nm||525 nm|
|Emission wavelength||695 nm||460 nm||530 nm||590 nm||575 nm|
|Sensitivity||0.03 µg l-1||0.100 ppb QSD||1 µg l-1||-||-|
|Range||0.03-75 µg l-1||0-100 ppb; 0-250 ppb||0-4000 µg l-1||-||-|
|Depth rating||600 m|
|Response time||0.17 s analogue; 0.125 s digital|
|Output||0-5 VDC analogue; 0-4095 counts digital|
Ashtech G12 Global Positioning System Receiver
The Ashtech G12 Global Positioning System (GPS) uses all-in-view tracking and 12 channels to provide real time three-dimensional positional measurements. It is Differential GPS (DGPS) ready, offering an accuracy of better than 40 cm, position latency better than 50 ms, and exact position latency to millisecond accuracy.
|Operating Temperature||-30°C to 70°C|
|Sampling frequency||up to 10 Hz|
|Real-Time Position Accuracy||Horizontal, DGPS: 40 cm Horizontal 95%: 90 cm Vertical 95%: 1.6 m|
Further details can be found in the manufacturer's specification sheet.
Ashtech Global Positioning System receivers (ADU series)
The ADU series of Global Positioning System (GPS) receivers are designed to give real-time three-dimensional position and attitude measurements. Attitude determination is based on differential carrier phase measurements between four antennas connected to a receiver, providing heading, pitch and roll, along with three-dimensional position and velocity.
The ADU2 model receives information from 48 channels, while the upgraded model (ADU5) uses 56 channels. The ADU5 also features a unique Kalman filter with user selectable dynamic modes to match operating conditions. It also incorporates signals from Satellite Based Augmentation Systems (SBAS) and features an embedded 2-channel 300 kHz beacon receiver for easy differential GPS (DGPS) operations.
Operational Temperature range:
| || |
|Sampling frequency||5 Hz||5 Hz|
| || |
Circular Error Probability:
| || |
The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.
- Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
- Beam diameter: 15 mm
- Transmitted beam collimation: <3 milliradians
- Receiver acceptance angle (in water): <18 milliradians
- Light source wavelength: usually (but not exclusively) 660 nm (red light)
The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.
A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.
Further details can be found in the manufacturer's Manual.
Falmouth Scientific Inc. Ocean Sensor Modules
FSI's individual sensor modules include an Ocean Conductivity Module (OCM), Ocean Temperature Module (OTM) and Ocean Pressure Module (OPM). All three use a low power micro-controller to collect, scale and transmit real-time data via RS-232 or RS-485.
|Parameter||OCM Conductivity||OTM Temperature||OPM Pressure|
|Range||0 - 7.0 S/m(0 - 70 mS/cm)||-2 to 32 °C||User Specified:0-200 dBar0-1000 dBar0-2000 dBar0-3000 dBar0-7000 dBar|
|Accuracy||-0.0003* S/m(-0.003 mS/cm)||-0.003 °C*||-0.03% full scale*|
|Stability /month||-0.00005 S/m(-0.0005 mS/cm)||-0.0005 °C||-0.002% full scale|
|Resolution||0.00001 S/m(-0.0001 mS/cm)||0.0001 °C||0.0004% full scale|
|Response at 1 m/s flow||50 msec||150 msec||25 msec|
|Sensor Type||Inductive cell||Platinum thermometer||Strain gauge|
* Higher accuracy available
For further details, see the manufacturer's specification sheet.
RAPID Cruise D279 Underway Surface Hydrography Instrumentation
Seawater was continually pumped from the hull of the ship at an approximate depth of 5m through the UKORS Surfmet system (known as the ship's non-toxic supply). The details of these sensors are shown in the table below.
|Sensor||Serial number||Last calibration date|
|FSI OCM housing conductivity sensor||1376||Calibration stored internally|
|FSI OTM housing temperature sensor||1340||25/06/2002|
|FSI OTM remote temperature sensor||1348||June 2003|
RAPID Cruise D279 Underway Meteorology, Surface Hydrography and Navigation Series
|Dates||4 April 2004 - 10 May 2004|
|Principal Scientific Officer||Dr Stuart Cunningham (SOC)|
|Cruise Report||Cunningham, S. A., 2005. RRS Discovery Cruise D279 04 APR - 10 MAY 2004. A Transatlantic hydrography section at 24.5°N. Southampton, UK, National Oceanoraphy Centre Southampton.(National Oceanography Centre Southampton Cruise Report No. 54).|
D279 travelled from Freeport in the Bahamas across the Atlantic to Tenerife in Spain. After initially focussing on the collection of chemical data from the Florida Current at 27°N, the main focus of the cruise was the collection of hydrographic data across the Atlantic Ocean between approximately 24 and 27.5°N.
It should be noted that the data series supplied by the originator covers 04 April to 08 May 2004, which is less that the duration of the cruise.
Data Processing Procedures
Two minute averaged sea surface hydrographic and meteorological data, together with navigation and bathymetric files, were transferred from PSTAR format into BODC internal format (QXF), using time (UTC) as the primary linking key, to allow use of the in-house visualisation tool (EDSERPLO). Reformatting and data calibration was carried out, and is discussed in the individual instrument sections. Each data channel was visually inspected and any spikes or periods of dubious data flagged as suspect. The capabilities of the workstation screening software allows comparative screening checks between channels.
The qxf file then underwent a further step. This involved using Matlab to split the qxf file into three separate qxf files. One contained data for hydrography, one for meterological data and the final qxf file held the navigation data.
RAPID Cruise D279 Underway Surface Hydrography Processing
Sea surface meteorology and thermosalinograph measurements were made by the UKORS Surfmet system. The depth of the ship's flow through intake is approximately 5 m and sent to the ship's central logging system. Onboard processing was carried out on a daily basis and involved running a sequence of executable programs. The initial stage transferred the underway surfmet data into PSTAR from RVS format. Subsequent processing included the calculation of salinity. Finally, Julian Day time variable data were calculated and the resulting data examined by plotting on a daily and weekly basis.
The underway salinity channel was calibrated by the originator using independent bottle salinity samples drawn from the ship's contaminated water supply at 2-8 hour intervals. The uncontaminated water supply wasn't available for sampling during this cruise due to low water pressure.
Calibration was achieved with a combination of PSTAR and Matlab routines. Bottle salinity data (.csv files) were transferred to the ship's Unix system and appended into one file. Salinities were converted back to conductivities and merged with 5 minute binned underway conductivity data. A 6 point running mean of conductivity offset was calculated in Matlab, and the calibration curve (with end point outliers excluded) applied to the original 2 minute averaged underway data. The mean offset applied (calibrated - uncalibrated salinity) was -0.11361 with a standard deviation of 0.009. Comparisons were also made between gridded 10 m CTD station and underway salinities (mean difference 0.002 with a standard deviation of 0.012).
The hull temperature data were calibrated against CTD temperature averaged over the top 5 m. Several outliers were identified and discarded on the basis that they had high standard deviations associated with them. In the remaining dataset, the offset (CTD temperature - underway temperature) was stable and did not show a relationship with time or temperature. The data were calibrated using a mean offset correction (N = 108, standard deviation = 0.03) as follows:
Calibrated temperature = temperature - 0.013.
Raw output voltages from the transmissometer were converted to beam attenuation after correction with readings taken at the time of sensor calibration. The equation used was:
Attenuation = -1/PL * ln((Transmissometer output * (1/Vref-Vd)) + (-Vd/Vref-Vd))
where PL = path length = 0.25 m; Vref = Voltage out in particle-free water = 4.826; Vd = Blocked path voltage = 0.057.
There were no samples against which to calibrate the fluorometer, so the fluorescence data remain as raw voltages and no further processing was possible.
Rapid Climate Change (RAPID) Programme
Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.
- To establish a pre-operational prototype system to continuously observe the strength and structure of the Atlantic Meridional Overturning Circulation (MOC).
- To support long-term direct observations of water, heat, salt, and ice transports at critical locations in the northern North Atlantic, to quantify the atmospheric and other (e.g. river run-off, ice sheet discharge) forcing of these transports, and to perform process studies of ocean mixing at northern high latitudes.
- To construct well-calibrated and time-resolved palaeo data records of past climate change, including error estimates, with a particular emphasis on the quantification of the timing and magnitude of rapid change at annual to centennial time-scales.
- To develop and use high-resolution physical models to synthesise observational data.
- To apply a hierarchy of modelling approaches to understand the processes that connect changes in ocean convection and its atmospheric forcing to the large-scale transports relevant to the modulation of climate.
- To understand, using model experimentation and data (palaeo and present day), the atmosphere's response to large changes in Atlantic northward heat transport, in particular changes in storm tracks, storm frequency, storm strengths, and energy and moisture transports.
- To use both instrumental and palaeo data for the quantitative testing of models' abilities to reproduce climate variability and rapid changes on annual to centennial time-scales. To explore the extent to which these data can provide direct information about the thermohaline circulation (THC) and other possible rapid changes in the climate system and their impact.
- To quantify the probability and magnitude of potential future rapid climate change, and the uncertainties in these estimates.
Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.
The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.
A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.
|Principal Scientist(s)||Stuart A Cunningham (Southampton Oceanography Centre)|
Complete Cruise Metadata Report is available here
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||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.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|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|
|O||Improbable value - user quality control|
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|