Metadata Report for BODC Series Reference Number 1028897


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 Brian King
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) Rapid Climate Change Programme
RAPIDMOC
Oceans 2025
RAPID-WATCH
Oceans 2025 Theme 1 WP1.2
Oceans 2025 Theme 10 SO3: MOC
 

Data Identifiers

Originator's Identifier OS75_DI346NNX_01
BODC Series Reference 1028897
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-01-06 07:39
End Time (yyyy-mm-dd hh:mm) 2010-02-18 10:34
Nominal Cycle Interval 150.0 seconds
 

Spatial Co-ordinates

Start Latitude 26.64140 N ( 26° 38.5' N )
End Latitude 37.93230 N ( 37° 55.9' N )
Start Longitude 79.07980 W ( 79° 4.8' W )
End Longitude 9.34440 W ( 9° 20.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 29.23 m
Maximum Sensor Depth 1053.3 m
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution Sensor fixed, measurements made at fixed depths - 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 Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum -
 

Parameters

BODC CODE Rank Units Short Title Title
BINNUMBR 0 Dimensionless BinNum Bin number
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
ACYCAA01 1 Dimensionless Record_No Sequence number
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
APEWGP01 1 Centimetres per second PlatformVelE_GPS Eastward velocity (over ground) of measurement platform by unspecified GPS system
APNSGP01 1 Centimetres per second PlatformVelN_GPS Northward velocity (over ground) of measurement platform by unspecified GPS system
DBINAA01 2 Metres BinDep Depth below sea surface (ADCP bin)
LCEWAS01 2 Centimetres per second CurrVelE_ADCP Eastward current velocity (Eulerian) in the water body by shipborne acoustic doppler current profiler (ADCP)
LCNSAS01 2 Centimetres per second CurrVelN_ADCP Northward current velocity (Eulerian) 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

Data Quality

During processing, the data originator noted the following issues with data quality:

Bubbles

Bubbles being present immediately below the transducer face can present a problem for ADCP data. There were few instances of bubbles creating problems during the cruise, apart from on 20 January 2010, when it is thought that the high velocities observed were spurious and caused by bubbles.

Anomalous Scattering Bias

A more extensive issue was the presence of anomalous scattering layers, created by light scattering particles such as zooplankton, leading to along-track velocity bias. On this cruise a large anomalous scattering layer was found between 460 and 660 metres across much of the section. The affected bins were not removed as this would also have removed good data.

Navigation

It was noticed that the navigation information had dropped out due to a splitter box problem. When this problem was fixed it was realised that the navigation data were not being fed to the VmDas system. The problem had begun at 23:15 28 January 2010. However, the data were logged in the TECHSAS system, so the navigation data were copied into the VMADCP data from the TECHSAS system.

On 28 January 2010, the navigation source was switched from the GPS4000 to the GPSG12 at approximately 23:20. However, the files after this period were found to again lack navigation data. This affected data from 23:20 28 January to 14:54 on 30 January, and once again the TECHSAS data were used to correct the navigation. At this point the navigation input was switched back to the GPS4000.


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

Instrument Description

A 75 kHz Teledyne RD Instruments Ocean Surveyor ADCP was fitted to the hull of the RSS Discovery, while docked in Freeport. The transducers were installed at a depth of 5.3 m.

The transducer is phased-array, which means that it is made up of many elements each transmitting in different phase. This is advantageous, because it means that the accuracy of the velocities, derived from the Doppler shifted signal is not affected by speed of sound changes throughout the water column.

The navigation data from the RRS Discovery GPS system was input into the VMADCP data; this was mainly from the Trimble 4000 GPS system. The blanking depth of the instrument was set to 8 m and the instrument was set to sample 60 bins, at 16 m depth per bin.

RD Instruments- Ocean Surveyor 75kHz Vessel mounted ADCP.

Long-Range Mode
Vertical Resolution Cell Size 3 Max. Range (m) 1 Precision (cm/s) 2
8m 520 - 650 30
16m 560 - 700 17
High-Precision Mode
Vertical Resolution Cell Size 3 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

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)

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

BODC Processing

The VMADCP data were provided to BODC as a single NetCDF file that covered a period from 07:39:35 on 06 January to 10:34:07 on 18 February 2010. This file was transferred to QXF format, which is a subset of NetCDF, using BODC generated Matlab code. It is BODC policy that ADCP data are reported from the middle of the ADCP depth bin. Using the formula:

Center of Bin = Transducer depth + Blank Depth + (Bin Depth/2)

it was found that the data provided were given to the bottom of the bin. BODC subtracted 8 from the depth to give the data at the middle of the bin.

During the transfer, the originator variables are mapped to BODC generated parameter codes and any variables that require unit conversion have the conversions applied. The parameter mapping and unit conversions can be seen in the table below.

Originator's variable Units Description BODC Parameter Code Units Comments
lon Degrees (0 - 360) Longitude ALONGP01 Degrees (-180 - +180) Values converted by subtraction of 360
lat Degrees (-108 - +180) Latitude ALATGP01 Degrees (-180 - +180) -
depth (of bin) m Depth of middle of ADCP bin DBINAA01 m Values converted by subtraction of 8
uabs cm s -1 Absolute East-West current velocity LCEWAS01 cm s -1 Eastern values are positive
vabs cm s -1 Absolute North-South current velocity LCNSAS01 cm s -1 Northern values are positive
uship m s -1 Ship's East-West velocity APEWGP01 cm s -1 Values converted by multiplication by 100. Eastern values are positive
vship m s -1 Ship's North-South velocity APNSGP01 cm s -1 Values converted by multiplication by 100. Northern values are positive
speed cm s -1 Scalar current speed - - Variable not transferred. Superseded by vector values
shipspd cm s -1 Scalar ship speed - - Variable not transferred. Superseded by vector values

Following transfer the data were screened using BODC in-house visualisation software. Any suspect data points were flagged with the appropriate BODC quality control flag.

Originator's Data Processing

The RRS Discovery cruise D346 took place between 05 January and 19 February 2010 and formed part of the RAPID-MOC project. Prior to the cruise a 75 kHz vessel-mounted Acoustic Doppler Current Profiler (ADCP) was fitted to the hull of the ship. The data from the instrument were acquired using RD Instruments VmDas software package version 1.42.

The instrument was run in narrowband single-ping mode and for the first few days, up to 09 January, it was run in bottom track mode to obtain an accurate phase and amplitude calibration. Typically, the instrument was switched between bottom tracking and water tracking close to 900 m. The final processing of the data was performed using the Common Ocean Data Access System (CODAS) provided by the University of Hawaii.

Calibration

The best calibration estimates are obtained when the velocity data is collected using the sea bed as a reference point. However, this is only possible when the sea bed is within range of the instrument. The ADCP was run in bottom tracking mode from 06 to 09 January and again when RRS Discovery reached the Moroccan continental shelf, in order to verify that the rotations had not altered during the section. The following calibration was applied to the data during bottom tracking mode.

Rotation angle = -2.88

Rotation amplitude = 1.002

The following calibration was applied to the data during water tracking mode.

Rotation angle = -2.1194

Rotation amplitude = 1.0015

The numbers are slightly different, but this is to be expected as it is difficult for the ship to maintain a fixed position while on station, due to a lack of dynamic propulsion. The calibrations were applied to the data before the data were inspected using the Gautoedit package within CODAS.


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

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:

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:

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)


Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.


RAPID- Will the Atlantic Thermohaline Circulation Halt? (RAPID-WATCH)

RAPID-WATCH (2007-2014) is a continuation programme of the Natural Environment Research Council's (NERC) Rapid Climate Change (RAPID) programme. It aims to deliver a robust and scientifically credible assessment of the risk to the climate of UK and Europe arising from a rapid change in the Atlantic Meridional Overturning Circulation (MOC). The programme will also assess the need for a long-term observing system that could detect major MOC changes, narrow uncertainty in projections of future change, and possibly be the start of an 'early warning' prediction system.

The effort to design a system to continuously monitor the strength and structure of the North Atlantic MOC is being matched by comparative funding from the US National Science Foundation (NSF) for the existing collaborations started during RAPID for the observational arrays.

Scientific Objectives

This work will be carried out in collaboration with the Hadley Centre in the UK and through international partnerships.

Mooring Arrays

The RAPID-WATCH arrays are the existing 26°N MOC observing system array (RAPIDMOC) and the WAVE array that monitors the Deep Western Boundary Current. The data from these arrays will work towards meeting the first scientific objective.

The RAPIDMOC array consists of moorings focused in three geographical regions (sub-arrays) along 26.5° N: Eastern Boundary, Mid-Atlantic Ridge and Western Boundary. The Western Boundary sub-array has moorings managed by both the UK and US scientists. The other sub-arrays are solely led by the UK scientists. The lead PI is Dr Stuart Cunningham of the National Oceanography Centre, Southampton, UK.

The WAVE array consists of one line of moorings off Halifax, Nova Scotia. The line will be serviced in partnership with the Bedford Institute of Oceanography (BIO), Halifax, Canada. The lead PI is Dr Chris Hughes of the Proudman Oceanographic Laboratory, Liverpool, UK.

All arrays will be serviced (recovered and redeployed) either on an annual or biennial basis using Research Vessels from the UK, US and Canada.

Modelling Projects

The second scientific objective will be addressed through numerical modelling studies designed to answer four questions:


Oceans 2025 Theme 1, Work Package 1.2: Atlantic Circulation and Transports

This Work Package is run by the National Oceanography Centre, Southampton (NOCS) and aims to establish whether the Atlantic Meridional Overturning Circulation (MOC) is slowing down, and to relate this to changes in regional storage of heat, freshwater and carbon.

More detailed information on this Work Package is available at pages 8 - 10 of the official Oceans 2025 Theme 1 document: Oceans 2025 Theme 1

Weblink: http://www.oceans2025.org/


Oceans 2025 Theme 10, Sustained Observation Activity 3: Monitoring the Atlantic Meridional Overturning Circulation

The Meridional Overturning Circulation (MOC) is the key component of ocean circulation in the Atlantic responding to climate change. Under the NERC directed programme Rapid Climate Change (RAPID) two arrays of instruments have been positioned in the ocean to monitor the MOC, one at 26.5 °N to capture the southward flow at depth, and the Western Atlantic Variability Experiment (WAVE) array across the Canadian-US continental slope, closer to the presumed source variations. Sustained Observation Activity (SO) 3 will continue these measurements to observe the strength and structure of the MOC, working closely with Oceans 2025 Theme 1 and the RAPID-WATCH directed programme.

There are two elements to this SO activity. SO 3.1. relates to the E-W mooring array in the mid-North Atlantic at 26.5 °N while SO 3.2. is concerned with the Western Atlantic array between Cape Cod and the Grand Banks.

Aims and Purpose of SO 3.1.

Aims and Purpose of SO 3.2.

More detailed information on this Work Package is available at pages 11 - 14 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/


Data Activity or Cruise Information

Cruise

Cruise Name D346
Departure Date 2010-01-05
Arrival Date 2010-02-19
Principal Scientist(s)Brian A King (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