Metadata Report for BODC Series Reference Number 1193161


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 National Oceanography Centre, Southampton
Processing Status banked
Project(s) RAPIDMOC
RAPID-WATCH
 

Data Identifiers

Originator's Identifier OS75_JC063
BODC Series Reference 1193161
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2011-09-01 19:18
End Time (yyyy-mm-dd hh:mm) 2011-09-10 06:28
Nominal Cycle Interval 300.0 seconds
 

Spatial Co-ordinates

Start Latitude 50.15780 N ( 50° 9.5' N )
End Latitude 28.47810 N ( 28° 28.7' N )
Start Longitude 5.05410 W ( 5° 3.2' W )
End Longitude 16.16340 W ( 16° 9.8' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 30.83 m
Maximum Sensor Depth 894.89 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 Approximate - Depth is only approximate
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
APEWZZ01 1 Centimetres per second PlatformVelE Eastward velocity (over ground) of measurement platform
APNSZZ01 1 Centimetres per second PlatformVelN Northward velocity (over ground) of measurement platform
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 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 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

RAPID cruise JC063/JC064 75kHz Shipboard ADCP data processing

Originator's processing

The following was taken from the JC064 cruise report. For more detailed information please refer to Cunningham (2011).

The 75kHz Ocean Surveyor ADCP is situated on the port drop keel of RRS James Cook . Data are acquired using the RD Instruments VmDas software package version 1.42. The ship's POSMV data stream was used as the accurate source of heading and position.

ADCP setup

Variable Setting
Number of Bins 48
Bin size 16m
Blank distance 8m
Transducer depth 6m
Processing mode Hi resolution short range
Maximum range 800m

Speed of sound considerations

In order to calculate water velocities, VMADCPs require an estimated value of sound speed. Temperature has the largest effect on sound speed; a change of 1°C in temperature affects up to 3 times more than a psu change of one unit. Sound speed only needs to be considered at transducer depth (Cunningham, 2011). The temperature needs to be compared to the measured remote temperature (tsg) and if the difference is over 1°C, corrections might be considered. Throughout this cruise, salinity was set at 35psu and the difference between the temperature at the transducer depth and the tsg was always less than 1°C. Thus no calibrations for sound speed were made.

Post-processing

The final processing of data was done using the CODAS (Common Ocean Data Access System) suite of software provided by the University of Hawaii. This suite of Python and Matlab programs allows manual inspection and removal of bad profiles and provides best estimates of the required rotation of the data, either from water profiling or bottom tracking. During this cruise, a new Matlab script enclosing all post processing steps was written, making the processing easier and faster.

Calibration

In order to obtain accurate horizontal velocities, it is vital to correct for heading errors. The navigation on the RRS James Cook is fed directly into VmDas from the Applanix POSMV, which incorporates a GPS heading source that is not sensitive to many of the heading errors that occur when gyrocompassses are used in isolation. Best calibration estimates are obtained when the velocity data are referenced to the bottom, however, these can only be obtained when the water depth is within 1.5 times the depth of the ADCP profiling range. During JC063 good quality bottom track was recorded on the wide continental shelf.

When the bottom can be detected, CODAS automatically estimates bottom track corrections of amplitude and angle phase. For this cruise the amplitude estimate was 1 and therefore did not need correcting. The phase correction was calculated to be -8.78°.

Interference

During the cruise, it was observed that the data quality was affected periodically at a changing depth. It is thought that this may be explained by other acoustic instruments with a similar frequency, creating a phased interference.

References

Cunningham, S. A. et al. 'RRS James Cook Cruise JC064, 10 Sep - 09 Oct 2011. RAPID moorings cruise report. Southampton, UK: National Oceanography Centre, Southampton, 183pp, National Oceanography Centre Cruise Report, No 14.'

BODC processing

The data were converted from Mstar format into BODC internal format, a netCDF subset, to allow use of in-house visualisation tools. The table below shows the mapping of originator variables to BODC Parameter codes.

Originator's variable Units Description BODC Parameter Code Units Comments
lon Degrees Longitude ALONGP01 Degrees -
lat Degrees Latitude ALATGP01 Degrees -
depth (of bin) m Depth of ADCP bin DBINAA01 m -
uabs cm s -1 Absolute Eastward current velocity LCEWAS01 cm s -1 -
vabs cm s -1 Absolute Northward current velocity LCNSAS01 cm s -1 -
uship m s -1 Ship's Eastward velocity APEWGP01 cm s -1 Values converted by multiplication by 100.
vship m s -1 Ship's Northward velocity APNSGP01 cm s -1 Values converted by multiplication by 100.
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

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.


Project Information

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)


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:


Data Activity or Cruise Information

Cruise

Cruise Name JC063
Departure Date 2011-09-01
Arrival Date 2011-09-10
Principal Scientist(s)Colin Day (National Marine Facilities Sea Systems), Stuart A Cunningham (National Oceanography Centre, Southampton)
Ship RRS James Cook

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