Metadata Report for BODC Series Reference Number 669248
No Problem Report Found in the Database
RAPID Cruise D279 150KHZ VMADCP Data Quality Report
Data visually inspected and found to be of good quality, with only a few isolated data spikes flagged.
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."
RD Instruments- Ocean Surveyor 150kHz Vessel mounted ADCP.
|Vertical Resolution Cell Size3||Max. Range (m)1||Precision (cm/s)2|
|4m||325 - 350||30|
|8m||375 - 400||19|
|Vertical Resolution Cell Size3||Max.Range (m)1||Precision (cm/s)2|
|4m||200 - 250||12|
|8m||220 - 275||9|
1 Ranges at 1 to 5 knots ship speed are typical and vary with situation.
2 Single-ping standard deviation.
3 User's choice of depth cell size is not limited to the typical values specified.
- Velocity long-term accuracy (typical): ±1.0%, ±0.5cm/s
- Velocity range: -5 to 9m/s
- # of depth cells: 1 - 128
- Max ping rate: 1.5
Maximum altitude (precision <2cm/s): 600m
Echo Intensity Profile
Dynamic range: 80dB
Transducer & Hardware
Beam angle: 30°
Configuration: 4-beam phased array
Communications: RS-232 or RS-422 hex-ASCII or binary output at 1200 - 115,200 baud
Output power: 1000W
Temperature (mounted on transducer)
- Range: -5° to 45°C
- Precision: ±0.1°C
- Resolution: 0.03°
Operating temperature: -5° to 40°C (-5° to 45°C)*
Storage temperature: -30° to 50°C (-30° to 60°C)*
*later instruments have greater range.
RAPID D279 150kHz VMADCP processing
The adcp is mounted 1.75m port of the keel, 33m aft of the bow and at a depth of approximately 5m.
Data were logged using IBM DAS. The 150kHz ADCP was configured to sample over 120 second intervals, with 64 bins of 8m thickness, and a blank beyond transmit of 4m. Where shallow water was encountered, the ADCP was operated in bottom track (BT) mode, otherwise it was operated in water track (noBT) mode.
Data Originator's Processing
Data were processed using the following scripts:
adpexec0: read raw data into P* format from the RVS level C; split into gridded depth dependent and non-gridded depth independent files; scale velocities to cm/s and amplitudes by 0.45 into dB; perform nominal edits and adjust bin depths to correct levels.
adpexec1: correct data timebase.
adpexec2_clock: merge data with Ashtech-gyro difference file and correct headings.
adpexec3: apply calibration values to the velocities, scaling speed by A and rotating directions by phi.
adpexec4: calculate absolute velocities by merging with bestnav navigation data and removing ship's speed over ground.
The ADCP uses its own clock that drifts by a few seconds per day. To correct this to match the ship's master clock, careful track was kept of the deviations between the two clocks. Data were processed in daily chunks and the clock corrections applied by linear interpolation from selected values spanning the day.
Calibration was undertaken using the following procedure:
- run through the normal processing steps as described above, with A=1 and phi=0 in adpexec3
- convert bottomew/bottomns into speed and direction
- convert ve/vn into speed and direction
- calculate A (=shipspd/botspd) and phi (=shipdirn-botdirn)
- select a valid subset of data and calculate mean A and phi
The calibration of the instrument relies on the collection of bottom track data, where the velocity of the bottom relative to the ship can be measured in water depths less than 1000m. This reduces the amount of data collected in the rest of the water column and therefore increases the noise in the measurements. Consequently, the instrument is swapped into bottom tracking mode only when appropriate.
It was noted that plots of absolute velocity vectors against time showed clear differences between on and off station. This is an indication of poor calibration. Examination of all bottom track data assembled together produced inconsistent estimates for A and phi. Consequently, because of the quality of the calibration for the 75kHz, it was decided to use that instrument to calibrate the 150kHz.
Comparison of aveaged relative velocities from the 150kHz and 75kHz ADCPs led to correction terms: dA = 0.985 (0.0142,104) and dphi = 0.0887 (0.71,94) and therefore an overall set of values of A = 0.9977 and phi = -0.2807.
Considerable problems were encountered in switching the ADCP on at the start of the cruise. On restart the slave synchronisation instruction was omitted and bottom tracking was permanently on.
BODC post-processing and screening
The data were converted from P* format into BODC internal format (QXF) to allow use of in-house visualisation tools.
Reformatted data were visually checked using the in-house editor EDSERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated quality control flag to 'M' for suspect values and 'N' for nulls.
Once quality control screening was complete, the data were archived in the BODC National Oceanographic Database and the associated metadata were loaded into an ORACLE Relational Database Management System.
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|