Metadata Report for BODC Series Reference Number 1108719


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Teledyne RDI Workhorse Long-Ranger ADCP  current profilers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Loic Jullion
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) ANDREX
 

Data Identifiers

Originator's Identifier JR_239_15
BODC Series Reference 1108719
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-03-27 18:16
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 60.19320 S ( 60° 11.6' S )
Longitude 50.54530 W ( 50° 32.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 10.0 m
Maximum Sensor Depth 1070.0 m
Minimum Sensor Height 39.0 m
Maximum Sensor Height 1099.0 m
Sea Floor Depth 1109.0 m
Sensor Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Unspecified -
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
ADEPZZ01 1 Metres DepBelowSurf Depth below surface of the water body
ASAMSCAL 1 Decibels ScaleAmpLADCP Scaled signal return amplitude from the water body by lowered acoustic doppler current profiler (ADCP)
ERRVLDCP 1 Centimetres per second LADCPErrVel Current velocity error in the water body by lowered acoustic doppler current profiler (ADCP)
LCEWLW01 1 Centimetres per second CurrVelE_ADCP Eastward current velocity (Eulerian) in the water body by lowered acoustic doppler current profiler (ADCP)
LCNSLW01 1 Centimetres per second CurrVelN_ADCP Northward current velocity (Eulerian) in the water body by lowered 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

Quality report

One of the beams of the LADCP broke suddenly after station 14, and was detected after station 20 during the originator's processing of the data. Although only three beams are necessary to calculate the three velocity components these tend to be less reliable. Therefore please note, that data from stations 14-20 are likely to be less reliable than the data from stations 2-13.


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

The LADCP data were collected using the instrumentation detailed below:

Sensor Model Serial Number Calibration (UT) Comments
LADCP RDI WorkHorse Monitor 13191 - Casts 1 to 20
LADCP RDI WorkHorse Monitor 12369 - Casts 20 onwards

The LADCP was configured to have a standard 10 x 16 m bins, with one water track and one bottom track ping in a two second ensemble, and a 5 m blank at the surface. Data were collected in beam coordinates and rotated to earth coordinates during post-processing. The instruments were mounted in a downward-looking orientation and positioned near the centre of a Sea-Bird 9 11 plus CTD frame.

One of the beams of the first LADCP broke suddenly after station 14, and was detected after station 20 during the processing of the data. The LADCP was then replaced after station 20. However, after station 20 there was a problem with a hardware bug which meant that heading was not being recorded. Therefore, only data before cast 20 have been provided.

Teledyne RDI's Workhorse Long Ranger ADCP

The Workhorse Long-Ranger acoustic doppler current profiler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented broadband signal (75 kHz) and a standard depth rating of 1500m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

The instrument comprises:

BODC Processing

The data were received in matlab format and converted into BODC internal format. Only u_nodetide and v_nodetide were retained in the QXF format, as u_bot and v_bot are processing steps used to correct u_nodetide and v_nodetide, whilst u_detide and v_detide have undergone subjective processing procedures. The following table shows how the variables within the matlab files were mapped to appropriate BODC parameter codes:

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
bottom m Depth of each station from CTD logsheet - - -
depth m Depth below sea surface in bins - - z_ladcp used for bin depth
lat Degrees Latitude - - -
lon Degrees Longitude - - -
pm - Unknown - - Empty cells
stat - Station number - - -
ts_ladcp dB Target strength of LADCP ASAMSCAL dB -
u_bot m s -1 Bottom track eastward velocity - - -
v_bot m s -1 Bottom track northward velocity - - -
u_ladcp_detide m s -1 De-tided eastward velocity - - -
v_ladcp_detide m s -1 De-tided northward velocity - - -
u_ladcp_nodetide m s -1 non-detided eastward velocity LCEWLW01 cm s -1 Units conversion from m s -1 to cm s -1
v_ladcp_nodetide m s -1 non-detided northward velocity LCNSLW01 cm s -1 Units conversion from m s -1 to cm s -1
uerr_ladcp m s -1 error velocity ERRVLDCP cm s -1 Units conversion from m s -1 to cm s -1
z_bot m Depths of bottom-track referenced velocity profile - - -
z_ladcp m Depth below sea surface in an array of bins ADEPZZ01 m -

All reformatted data were visualised using the in-house Edserplo software. Suspect and missing data were marked by adding an appropriate quality control flag.

Note that u_bot and v_bot bottom track data are available on request.

Originator's Data Processing

Sampling Strategy

A total of 98 LADCPs were deployed, however only 18 LADCPs proved unproblematic. Station 1 was a test station which comprised of one downward-looking and one upward-looking LADCP deployed simultaneously. However, given the number of stations scheduled and the tendency of LADCPs to fail rather quickly, the originators decided to use only a downward-looking instrument for the rest of the cruise. Data from the test station was not provided. Station 5 was aborted as the CTD was giving bad data and the station was repeated shortly after (named station 6).

Prior to each station the ADCP was connected to a laptop in the deck lab for pre-deployment tests and the instrument was programmed. After each station the instrument was reconnected to the laptop for the retrieval of the data. The battery package was charged between stations. The raw data for each station were downloaded from the instrument and copied into a central data directory.

Processing

Processing was carried out using LDEO LADCP processing software version 7b (Visbeck, 2002) and was used to; correct for sound speed using the CTD calibrated data, calculate the barotropic velocity from the ship position at the beginning and end of the cast, and exclude bad quality data (large tilt of the CTD package, low backscatter etc). Please refer to Visbeck (2002) for further processing details.

References

Visbeck, M., 2002. Deep velocity profiling using Lowered Acoustic Doppler Current Profilers: Bottom track and inverse solutions. Journal of Atmospheric Oceanic Technology, 19, 794?807.


Project Information

Antarctic Deep Water Rates of Export (ANDREX) project document

ANDREX is a UK field programme aimed at investigating the role of the Weddell Gyre in the Meridional Overturning Circulation (MOC) and its influence on deep ocean properties.

The MOC is a critical regulator of Earth's climate and is crucial for deep water ventilation across the globe. Surface currents transport waters towards the poles, where they become dense and sink, flowing equatorward as deep, cool currents. The MOC ensures that the deep oceans remain ventilated and conducive to life, and is also important for anthropogenic carbon sequestration. The southern closure of the MOC in the Weddell Sea is strongly influenced by the Weddell Gyre, which facilitates the exchange of waters between the Antarctic Circumpolar Current (ACC) and the waters of the continental shelf. Cooling and sea ice formation in the Weddell Sea lead to overturning of the water column and the ventilation of Antarctic Bottom Water (AABW), which flows out of the Weddell Sea and into the deep oceans to the north. Thus, the Weddell Gyre plays an important role in the properties of deep ocean waters on a global scale.

The goals of ANDREX are to investigate the exchange of water masses between the ACC and the Weddell Sea, including AABW formation and ventilation rates, carbon and nutrient cycling, the influence of fresh water input from sea ice, precipitation and glacial melt, and the role of the Weddell Gyre in anthropogenic carbon sequestration. The project includes hydrographic, ventilation tracer, biogeochemical and bathymetric measurements along the outer rim of the Weddell Gyre.

ANDREX is funded by the UK Natural Environment Research Council (NERC) Antarctic Funding Initiative (AFI) and involves scientists from the National Oceanography Centre, Southampton (NOC), the British Antarctic Survey (BAS), the University of East Anglia (UEA), the University of Manchester, the Alfred Wegener Institut (AWI) and the Woods Hole Oceanographic Institution (WHOI).

For more information please see the official project website at ANDREX


Data Activity or Cruise Information

Cruise

Cruise Name JR20100319 (JR235, JR236, JR239)
Departure Date 2010-03-19
Arrival Date 2010-04-24
Principal Scientist(s)Mike Meredith (British Antarctic Survey)
Ship RRS James Clark Ross

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