Metadata Report for BODC Series Reference Number 808810
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
Data Description |
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Time Co-ordinates(UT) |
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Parameters |
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Problem Reports
No Problem Report Found in the Database
Data quality
The channels LERRAS01, LRZAAS01, LCEWAS01, LCNSAS01 are noisy. Although no specific values are flagged the data should be used with caution due to the level of noise.
Data Access Policy
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."
Narrative Documents
RD Instruments 150kHz Narrow Band Acoustic Doppler Current Profiler
Specifications
| Water velocity measurements relative to the ADCP | |
|---|---|
| Accuracy (long term) | 0.5 % of measured velocity ± 0.5 cm/s |
| Statistical uncertainty for one ping (cm/s) | Depth cell length of 4, 8, 16 m = 26, 13, 6.5 respectively (for horizontal velocities using the standard transducer) |
| Ping rate (pings per second) | 2 (100 pings averaged in ADCP) |
| Maximum profiling range (meters) | 290 |
| Minimum range to start of first depth cell (meters) | 4 |
| Number of depth cells | 8 to 128 |
| Velocity range | ± 0.01 to 9.5 m/s (horizontal) |
| Velocity resolution (cm/s) | 0.25 or 0.125 |
| Velocity measurements relative to the bottom and measurement of bottom depth | |
| Accuracy | 0.5% of measured velocity ± 0.5 cm/s |
| Statistical uncertainty of one ping (percent of measured velocity) | 3.5 (for horizontal velocities using the standard transducer) |
| Ping rate (pings per second) | 0.9 (100 pings averaged in ADCP) |
| Depth range | 290 (the maximum depth range can be up to 1.5 times greater than specified) |
| Bottom depth resolution (meters) | 4 |
| Velocity range | ± 0.01 to 9.5 m/s (horizontal) |
| Velocity resolution (cm/s) | 0.25 or 0.125 |
| Measurement of echo intensity | |
| Accuracy (with temperature correction) | Before calibration : ± 8 dB, After calibration: ± 3 dB |
| Statistical uncertainty for one ping | Approximately ± 5 dB |
| Ping rate (pings per second) | 2 (100 pings averaged in ADCP) |
| Profiling range (meters less than for water velocity measurement) | 64 |
| Number of depth cells | 8 to 128 |
| Dynamic range | 80 dB |
| Resolution | 0.45 dB typical (temperature/system dependent) |
| Data communication | |
| Interface | Modified RS-232/422 serial at baud rates of 300-19,200 |
| Data format | Binary (8-bit) or ASCII (76-character) lines separated by a carriage return/line feed. |
| Data storage capacity | 2 MB (standard); expandable to 40 MB in 1 and/or 2 MB increments |
| Power requirements | |
| ADCP electronics | Voltage range (VDC) 6-12; Standby current (amps) 0.0002; Operate current (amps) 0.24; Peak current (amps) 0.5 |
| transmit and EPROM recorder | Voltage range (VDC) 20-40; Standby current (amps) 0.0001; Operate current (amps) 0.10; Peak current (amps) 2.0 |
| CTD sensors | Voltage range (VDC) 12-20; Standby current (amps) 0.0001; Operate current (amps) 0.022; Peak current (amps) 0.05 |
| Temperature sensor | |
| Accuracy | ± 0.2°C |
| Time constant | Approximately 2 minutes |
| Range | -5° to 45°C |
| Resolution | 0.012°C |
| Environmental | |
| Operating temperature | -5°C to 40°C |
| Humidity | Must be non-condensing |
| Depth capability | 35 meters (transducer only) |
| Physical characteristics | |
| Weight in air | 67.6 kg |
| Weight in water | 25.0 |
| Diameter | 45.9 cm |
| Length | 141.4 cm |
RAPID cruise D309-310 150 kHz Shipboard ADCP data: BODC processing
The data were provided to BODC in PStar format with the files named as adp309##.abs, where ## is the daily file number (from 1 -17). The files are transferred to a netcdf format by following BODC transfer procedures. The transfer involves mapping the originator's variables to unique BODC parameter codes. The parameter mapping can be seen below.
| Originator's variable | Description | Units | Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| lat | Latitude (+ve N) | Degrees | ALATTR01 | Degrees | - |
| lon | Longitude (+ve E) | Degrees | ALONTE01 | Degrees | - |
| evelcal | Eastward velocity | cms-1 | LREWAS01 | cms-1 | Relative to ship |
| nvelcal | Northward velocity | cms-1 | LRNSAS01 | cms-1 | Relative to ship |
| ve | Ship's eastward velocity | cms-1 | APEWTR01 | cms-1 | - |
| vn | Ship's northward velocity | cms-1 | APNSTR01 | cms-1 | - |
| absve | Absolute eastward velocity | cms-1 | LCEWAS01 | cms-1 | - |
| absvn | Absolute northward velocity | cms-1 | LCNSAS01 | cms-1 | - |
| velvert | Upward velocity | cms-1 | LRZAAS01 | cms-1 | - |
| velerr | Velocity error | cms-1 | LERRAS01 | cms-1 | - |
| amp1 | Amplitude | decibar | ASAMAS01 | decibar | - |
| good | Percentage good signal return | % | PCGDAP01 | % | - |
Detailed metadata and documentation are linked to the data.
Data quality procedures are then performed on the files using BODC generated in house visualisation tools.
RAPID cruise D309-310 150 kHz Shipboard ADCP data: Originator's processing
A 150 kHz ADCP is hull mounted 1.75 m to port of the keel and 33 m aft of the bow at an approximate depth of 5 m.
Navigation data is usually obtained from a BestNav system which uses a hierarchy of GPS devices to constantly give the most accurate positional data. However, the BestNav system was not used during the cruise as it was judged to be giving questionable output. A high quality navigation file was obtained from a GPS Trimble 4000 system with an Ashtech G12 system providing differential corrections.
Data from the ADCP were logged using RDI Data Acquisition Software (DAS) version 2.48 with profiler firmware 17.20. The instrument sampled over 120 second intervals with 96 bins of 4 m thickness, pulse length 4 m and a blank beyond transmit of 4 m. At the beginning of the cruise, the ADCP was switched on to bottom track mode over the continental shelf to enable calibration of the instrument. This resulted in the following calibration being applied:
tanØ = 0.0153 (±s.d = 0.0060),Ø = 0.8740o and A = 0.9983 (±s.d = 0.0057)
Where Ø is the misalignment angle and A is the Scaling Factor.
The ADCP had been refitted while RRS Discovery was in dry dock to a heading offset of approximately 45o. This offset is accounted for in the DAS software. On previous cruises the ADCP PC clock had been synchronised with the ship's master clock but this was not the case on this cruise. This resulted in a steady drift of approximately 4 s a day. Time checks were made every 24 hours and the time offset was accounted for in the subsequent Matlab processing files to give the correct time in the output files. In addition, all velocities where the percentage of good signal return variable was 25% or less are deleted by the ADCP Matlab software.
More detailed information can be found in the D309-310 cruise report
Project Information
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.
Scientific Objectives
- 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.
Projects
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.
RAPID - Cape Farewell and Eirik Ridge: Interannual to Millennial Thermohaline Circulation Variability
This project was funded under the NERC Rapid Climate Change Programme, grant number NER/T/S/2002/00453. Dr. Sheldon Bacon (Southampton Oceanography Centre) was the Principal Investigator, with co-Investigators from the University of Southampton, Prof. D. A. Stow and Dr. E. J. Rohling. The project started in December 2003 and ended in November 2008.
The project used a combination of hydrography and palaeoceanography measurements to determine the spectrum of variability of the Deep Western Boundary Current, on timescales from days to millennia. The project focused on deglacial to Holocene variability; in particular, seeking to characterise the onset and endings of three cold periods: the Younger Dryas (YD; 12.5-11.5 ka BP), the ~8.2 ka event, and the Little Ice Age (LIA; 16th-19th century AD).
The objectives of the project included:
- Defining the THC response to Holocene climate variability by a highly resolved investigation of palaeoceanographic/climate proxies in sediment cores
- Developing high-resolution sediment proxies for bottom current speed
- Absolute calibration of sediment proxies for bottom current speed
- Defining the relationship between drift construction and the bottom current regime
- Improved definition of present-day ocean circulation and climate
Most of the fieldwork was carried out on 2 cruises in the Cape Farewell and Irminger Sea vicinity:
| Cruise | Start | End | Comments |
|---|---|---|---|
| D298 | 2008-08-23 | 2005-09-05 | Work included mooring deployments, sediment coring, sampling for isotopes and CTD casts |
| D309-310 | 2006-08-18 | 2006-09-05 | Work included mooring turn-arounds and CTD casts. |
Data Activity or Cruise Information
Cruise
| Cruise Name | D309-310 |
| Departure Date | 2006-08-18 |
| Arrival Date | 2006-09-05 |
| Principal Scientist(s) | Sheldon Bacon (National Oceanography Centre, Southampton) |
| Ship | RRS Discovery |
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:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | 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.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| 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 |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
SeaDataNet Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| 0 | no quality control |
| 1 | good value |
| 2 | probably good value |
| 3 | probably bad value |
| 4 | bad value |
| 5 | changed value |
| 6 | value below detection |
| 7 | value in excess |
| 8 | interpolated value |
| 9 | missing value |
| A | value phenomenon uncertain |
| B | nominal value |
| Q | value below limit of quantification |
