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Metadata Report for BODC Series Reference Number 684405


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Teledyne RDI 150kHz Narrowband Vessel-Mounted ADCP  current profilers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Stuart Cunningham
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Rapid Climate Change Programme
RAPIDMOC
 

Data Identifiers

Originator's Identifier ADP17701
BODC Series Reference 684405
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2005-11-14 08:29
End Time (yyyy-mm-dd hh:mm) 2005-11-16 07:56
Nominal Cycle Interval 120.0 seconds
 

Spatial Co-ordinates

Start Latitude 44.06400 N ( 44° 3.8' N )
End Latitude 35.82333 N ( 35° 49.4' N )
Start Longitude 10.24950 W ( 10° 15.0' W )
End Longitude 13.50817 W ( 13° 30.5' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 17.0 m
Maximum Sensor or Sampling Depth 329.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
Sea Floor Depth Source -
Sensor or Sampling Distribution Sensor fixed with measurements made at multiple depths within a fixed range (e.g. ADCP) - The sensor is at a fixed depth, but measurements are made remotely from the sensor over a range of depths (e.g. ADCP measurements)
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum -
 

Parameters

BODC CODERankUnitsTitle
DBINAA010MetresDepth (spatial coordinate) of ADCP bin relative to water surface {bin depth} in the water body
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ALATGP011DegreesLatitude north relative to WGS84 by unspecified GPS system
ALONGP011DegreesLongitude east relative to WGS84 by unspecified GPS system
APEWGP012Centimetres per secondEastward velocity of measurement platform relative to ground surface by unspecified GPS system
APNSGP012Centimetres per secondNorthward velocity of measurement platform relative to ground surface by unspecified GPS system
ASAMAS012DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP)
LCEWAS012Centimetres per secondEastward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)
LCNSAS012Centimetres per secondNorthward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)
LERRAS012Centimetres per secondError velocity of water current in the water body by shipborne acoustic doppler current profiler (ADCP)
LREWAS012Centimetres per secondEastward velocity of water current relative to moving platform in the water body by shipborne acoustic doppler current profiler (ADCP)
LRNSAS012Centimetres per secondNorthward velocity of water current relative to moving platform in the water body by shipborne acoustic doppler current profiler (ADCP)
LRZAAS012Centimetres per secondUpward velocity of water current in the water body by shipborne acoustic doppler current profiler (ADCP)
PCGDAP012PercentAcceptable proportion of acoustic signal returns from the water body by acoustic doppler current profiler (ADCP)

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data Quality Report

The data in general are quite noisy. High platform velocities should be borne in mind when using these data.


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 CD177 150kHz VMADCP processing

Configuration

Data were logged using IBM DAS. The 150kHz ADCP was configured to sample over 30 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 acquisition

    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 : applies clock corrections to the above two files.

    • adpexec2 : 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.

    • calexec0 : determines GPS derived ship speed and ADCP derived ship speed from relative water velocity. Also validates ADCP velocities against GPS velocities.

    • adpexec4 : calculate absolute velocities by merging with bestnav navigation data and removing ship's speed over ground.

  • Calibration

    The two calibration constants required by adpexec3 are the time mean values A and phi. The normal calibration method is 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

    This best method of 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. However such data were not available on this cruise as the ship spent most of its time in deep water. A less satisfactory approach had to be used that assumes that over a long enough time interval the currents (absolute water velocities) will integrate to zero. Of course in practice this may not be the case.

    Under this assumption the relative water velocity - the sum of the ships velocity relative to the bottom plus the velocity of actual currents - is used to determine GPS ship speed and ADCP ship speed to gain the calibration coefficient. Script calexec0 was developed to do this.

    • input master navigation data and ADCP data file
    • calculate (A) ship speed and bottom speed and (phi) ship direction and bottom direction using pcmcal
    • A and phi are computed and output
    • Temporal means of A and phi output

    The initial values are unlikely to be the best choice for A and phi so the actual time-series was inspected and a time interval over which A and phi were relatively constant was used to determine the calibration values.

    The calibration values for this cruise were A = 1.018 and phi = 4.640 calculated over time interval t = 27547744s to t = 27583743s

BODC post-processing and screening

  • Reformatting

    The data were converted from P* format into BODC internal format (QXF) to allow use of in-house visualisation tools.

  • Screening

    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.

  • Banking

    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.


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.


Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)

Scientific Rationale

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

References

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)


Data Activity or Cruise Information

Cruise

Cruise Name CD177
Departure Date 2005-11-12
Arrival Date 2005-11-29
Principal Scientist(s)Stuart A Cunningham (National Oceanography Centre, Southampton)
Ship RRS Charles Darwin

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
Q value below limit of quantification