Metadata Report for BODC Series Reference Number 1051083
No Problem Report Found in the Database
RAPID Cruise D277 Underway Surface Hydrography Data Quality Report
Fluoresence and chlorophyll concentration
Users should note that chlorophyll concentration was derived from manufacturer's coefficients and not from calibration against field samples. Therefore the absolute values should be used with caution. There are occaisions when chlorophyll concentration is negative, especially from 02/03/2004 until the end of the series. All negative values have been flagged suspect. It is likely that the calibration used to derive chlorophyll concentration has introduced an offset resulting in negative values at very low concentrations.
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|
RAPID Cruise D277 Underway Surface Hydrography Instrumentation
Seawater was continually pumped from the hull of the ship at an approximate depth of 5m through the various underway sensors (known as the ship's non-toxic supply). The details of the 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|
|SeaTech transmissometer (path length 25cm)||CST-113R||31/05/1996|
RAPID Cruise D277 Underway Surface Hydrography Processing
Thermosalinograph (TSG) system measurements were sent along with meterological measurements 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 data from raw RVS format to PSTAR format. Subsequent processing included the calculation of salinity and the merging of different data streams. Julian Day time variable date were calculated and the resulting data examined by plotting on a daily and weekly basis.
The underway salinity channel was calibrated 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 of the salinity channel 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 -0.13648 with a standard deviation of 0.009. Comparisons were also made between gridded 10 m CTD station and underway salinities (mean difference -0.003 with a standard deviation of 0.009).
The data were supplied to BODC as 2 minute averages in PSTAR format.
The data files received were transferred from PSTAR format into BODC's in-house NetCDF format to allow use of the in-house visualisation tool (EDSERPLO). The transfer process also includes the flagging of data which fall outside of the range of acceptable values for each parameter. Ship's navigation data were merged with underway sea surface hydrography using time as the primary linking key.
Each data channel was visually inspected and any spikes or periods of dubious data flagged as suspect. The capabilities of the screening software allows all possible comparative screening checks between channels.
Salnity data were calibrated by the data originator, as described above.
The hull temperature data were verified by the originator against the CTD temperature data and were found to be in agreement throughout the cruise. No calibrations were applied.
Transmissometer data were supplied as raw voltages. On screening the data, BODC found the logged values were erroneous throughout and the channel was subsequently excluded from the series.
Fluoresence data were supplied to BODC as raw voltages. The manufacturer's calibration was obtained from the sensor specification sheet and used to convert fluorescence into chlorophyll concentration as follows: Concentration = (Vsample-Vblank)*Scale Factor where Vblank = 0.062 and scale factor = 14.2.
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.
Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)
There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:
- A mooring array spanning the Atlantic at 26.5°N to measure the southward branch of the MOC (Hirschi et al., 2003 and Baehr et al., 2004).
- Additional moorings deployed in the western boundary along 26.5°N (by Prof. Bill Johns, University of Miami) to resolve transport in the Deep Western Boundary Current (Bryden et al., 2005). These moorings allow surface-to-bottom density profiles along the western boundary, Mid-Atlantic Ridge, and eastern boundary to be observed. As a result, the transatlantic pressure gradient can be continuously measured.
- Monitoring of the northward branch of the MOC using submarine telephone cables in the Florida Straits (Baringer et al., 2001) led by Dr Molly Baringer (NOAA/AOML/PHOD).
The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.
The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:
- Eastern Boundary (EB) array defined as a box with the south-east corner at 23.5°N, 25.5°W and the north-west corner at 29.0°N, 12.0°W
- Mid Atlantic Ridge (MAR) array defined as a box with the south-east corner at 23.0°N, 52.1°W and the north-west corner at 26.5°N, 40.0°W
- Western Boundary (WB) array defined as a box with the south-east corner at 26.0°N, 77.5°W and the north-west corner at 27.5°N, 69.5°W
Baehr, J., Hirschi, J., Beismann, J.O. and Marotzke, J. (2004) Monitoring the meridional overturning circulation in the North Atlantic: A model-based array design study. Journal of Marine Research, Volume 62, No 3, pp 283-312.
Baringer, M.O'N. and Larsen, J.C. (2001) Sixteen years of Florida Current transport at 27N Geophysical Research Letters, Volume 28, No 16, pp3179-3182
Bryden, H.L., Johns, W.E. and Saunders, P.M. (2005) Deep Western Boundary Current East of Abaco: Mean structure and transport. Journal of Marine Research, Volume 63, No 1, pp 35-57.
Hirschi, J., Baehr, J., Marotzke J., Stark J., Cunningham S.A. and Beismann J.O. (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophysical Research Letters, Volume 30, No 7, article number 1413 (DOI 10.1029/2002GL016776)
|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|