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Metadata Report for BODC Series Reference Number 669826


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Teledyne RDI Ocean Surveyor 75kHz vessel-mounted ADCP  current profilers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Stuart Cunningham
Originating Organization Southampton Oceanography Centre (now 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 SUR27773
BODC Series Reference 669826
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2004-03-13 00:01
End Time (yyyy-mm-dd hh:mm) 2004-03-13 23:59
Nominal Cycle Interval 120.0 seconds
 

Spatial Co-ordinates

Start Latitude 26.51233 N ( 26° 30.7' N )
End Latitude 26.49017 N ( 26° 29.4' N )
Start Longitude 73.68883 W ( 73° 41.3' W )
End Longitude 76.08117 W ( 76° 4.9' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 21.0 m
Maximum Sensor or Sampling Depth 965.0 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)
ASAMSP002DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 1
ASAMSP022DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 2
ASAMSP032DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 3
ASAMSP042DecibelsSignal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP) beam 4
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)

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

RAPID Cruise D277 75KHZ VMADCP Data Quality Report

Data visually inspected and found to be of generally good quality with very few suspect data points flagged.

Null values noted for LCEWAS01, LCNSAS01,LREWAS01, LRNSAS01,LRZAAS01 and LERRAS01 parameters from 12/03/04 00:01:10 until 12/03/04 06:51:10 on series 669814.

Series 669795 has increase in bins from 40 to 60 (equivalent in a depth increase from 645m to 757m) on March 10 at approximately 17:30.


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- Ocean Surveyor 75kHz Vessel mounted ADCP.

Long-Range Mode
Vertical Resolution Cell Size3 Max. Range (m)1 Precision (cm/s)2
8m 520 - 650 30
16m 560 - 700 17
High-Precision Mode
Vertical Resolution Cell Size3 Max. Range (m)1 Precision (cm/s)2
8m 310 - 430 12
16m 350 - 450 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.

Profile Parameters

  • Velocity long-term accuracy (typical): ±1.0%, ±0.5cm/s
  • Velocity range: -5 to 9m/s
  • # of depth cells: 1 - 128
  • Max ping rate: 0.7

Bottom Track

Maximum altitude (precision <2cm/s): 950m

Echo Intensity Profile

Dynamic range: 80dB
Precision: ±1.5dB

Transducer and 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

Standard Sensors

Temperature (mounted on transducer)

  • Range: -5° to 45°C
  • Precision: ±0.1°C
  • Resolution: 0.03°

Environmental

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.

Web Page

Further details can be found on the manufacturer's website or in the specification sheet

RAPID D277 75kHz VMADCP processing

Configuration

The adcp is mounted 0.75m to starboard of the keel and 28.85m aft of the bow. Due to the positioning, this adcp is prone to bubble contamination when the ship is pitching and therefore depth coverage and quality deteriorates noticeably in rough seas.

Data were logged on a PC using RDI data acquisition software (version 1.3). The 75kHz ADCP was configured to sample over 120 second intervals, with 60 bins of 16m thickness, and a blank beyond transmit of 8m. Data were then averaged into 2 minute files. The software logs the PC clock time and its offset from GPS time. This offset was applied to the data during processing, before merging with navigation. Gyro heading and GPS Ashtech heading, location and time were fed as NMEA messages into the software, which was configured to use the gyro heading for coordinate transformation.

Data Originator's Processing

  • Data acquisition

    Data were logged on the OS75 PC and transferred by ftp to a UNIX workstation for processing. The following scripts were then run:

    • surexec0: read data into PSTAR format from RDI binary format; write water track data into files of the form sur277nn.raw and equivalent, where nn is a two character code; write bottom track data where present into files of the form sbt277mm; scale velocities to cm/s and amplitude by 0.45 to dB; correct time variable by combining GPS and the PC times; set the depth of each bin.

    • surexec0b: creates daily files.

    • surexec1: edit data(status flag equal to 1 is bad data); edit on percent good variable; move ensemble time to the end of its interval.

    • surexec2: merge data with Ashtech-gyro difference file and correct heading.

    • surexec3: calibrate velocities by scaling by factor A and rotating by angle phi.

    • surexec4: calculate absolute velocities by merging with navigation data (bestnav) and removing the ship's velocity over ground from the ADP data.

  • Calibration

    Calibration was undertaken using the following procedure:

    • run through the normal processing steps as described above, with A=1 and phi=0 in surexec3
    • 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.

    The data were calibrated using all the available data from D277 and the data from D279. Calculation of the mean A and phi from spot values was undertaken by choosing good input data by visual inspection of the values. Two extra values were calculated: the minimum range (from each of the four transducers) to the bottom and the absolute difference of the minimum and maximum ranges. Records of data were included in the averaging if they occurred in a consecutive sequence of records, which involved stable heading, Ashtech correction and ship's speed, and if the range difference was less than 15m. The data were plotted and outliers removed and A and phi values averaged. The resulting calibration values were: A = 1.004 and phi = -60.12 with standard deviations 0.007 and 0.44 respectively.

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. One channel was not taken through the reformatting stage. The originator's identifier for this channel was "good3bm".

  • Parameter codes

    All variables were assigned a BODC 8-character parameter code. This code gives information about the variable, for example the method of acquisition and the units of the data.

  • 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 D277
Departure Date 2004-02-26
Arrival Date 2004-03-16
Principal Scientist(s)Stuart A Cunningham (Southampton Oceanography Centre)
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
Q value below limit of quantification