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Metadata Report for BODC Series Reference Number 705325


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Teledyne RDI 300kHz Workhorse Monitor direct-reading ADCP  current profilers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Martin Price
Originating Organization University of East Anglia School of Environmental Sciences
Processing Status banked
Project(s) Autosub Under Ice
 

Data Identifiers

Originator's Identifier JR97_LADCP_J016_02
BODC Series Reference 705325
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2005-02-14 00:52
End Time (yyyy-mm-dd hh:mm) 2005-02-14 01:19
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 70.02800 S ( 70° 1.7' S )
Longitude 1.53750 W ( 1° 32.3' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor Depth 40.0 m
Maximum Sensor Depth 420.0 m
Minimum Sensor Height 23.0 m
Maximum Sensor Height 403.0 m
Sea Floor Depth 443.0 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 Approximate - Depth is only approximate
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
DEPHPR01 1 Metres CmpDep Depth below surface of the water body by profiling pressure sensor and converted to seawater depth using UNESCO algorithm
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)
NLADCPBN 1 Dimensionless Num_LADCP_bin Number (per bin) of measurements by lowered acoustic doppler current profiler (ADCP)
SDEWLW01 1 Centimetres per second Std_dev_EW_LADCP Eastward current velocity standard deviation (Eulerian) in the water body by lowered acoustic doppler current profiler (ADCP)
SDNSLW01 1 Centimetres per second Std_dev_NS_LADCP Northward current velocity standard deviation (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


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

Teledyne RDI's Workhorse Monitor ADCP

The Workhorse Monitor acoustic doppler current profler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented four beam signal (300, 600 or 1200 kHz) and a standard depth rating of 200m or 600m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

James Clark Ross JCR97 Lowered Acoustic Doppler Current Profiler data

Originator's processing

Full instructions for LADCP deployment and recovery during JCR97, details of the configuration files and, more information on the issues encountered can be found in the Cruise report

The following is adapted from the cruise report section written by Kevin Oliver and Justin Buck.

The LADCP package used during JCR97 consisted of a downward and an upward looking RDI 300 kHz Workhorse (WH) ADCP. The downward-looking Workhorse (DWH; serial number 4908) was mounted off-centre at the bottom of the frame, and the upward-looking Workhorse (UWH; serial number 1855) was mounted on the outside of the frame. The details of their sampling configurations are described in the secion below. Between stations, each ADCP was usually connected to a controlling PC in the Underway Instrument Control (UIC) room through a serial cable for delivery of pre-deployment instructions and post-deployment data retrieval. When sea-ice necessitated lowering the package from the aft of the ship, this was impossible due to insufficient length of cable, and the ADCPs were allowed to continue pinging between stations. The battery package was recharged after each deployment, by connection to a charging unit in the UIC room via a power lead.

Both instruments were deployed during every station except for station 79. At every station except the test station (station 999), where no data were obtained as a result of a minor error in the command file for the master DWH, both ADCPs returned reasonable raw data. The data quality during downcasts/upcasts was poorer during stations 62-72 and 82 when alternative sampling configurations were used (see configuration section below). For other stations, inspection typically revealed better agreement with the shipboard ADCP for DWH downcasts than DWH upcasts.

Processing of data from each Workhorse was carried out independently using the same University of Hawaii (UH; Eric Firing's group) software that was used on JCR106 and JCR80, detailed in the processing section. Because problems were encountered, the data were also processed using software by Lamont Doherty Earth Observatory (LDEO; Martin Visbeck's group). Use of this software is not detailed here. Because tables of the earth's magnetic variation were not updated to 2005 in the UH software, the magnetic field information for the equivalent date in 2004 was used. The error associated with this is likely to be smaller than the precision of the ADCP compasses, and was not detectable from comparison with the LDEO software output for the DWH. There was good agreement between raw data from the DWH and the UWH. Raw outputs showed good agreement on spatial scales greater than the range of the ADCPs but negative correlation on smaller spatial scales. On this basis, it is suspected that the UH software was either treating the UWH as a DWH, or was misinterpreting the bin distances from the UWH. Modification of the LDEO software has provided processed UWH data that agree well with DWH data.

JCR97 LADCP configuration files

Three different sampling configurations were used for different stations, depending on the primary purpose for which the ADCPs were used. The majority of stations consisted of conventional single down-and-up casts with pauses for bottle firing. For such stations, as well as for 'yoyo' stations (stations 26-28), consisting of multiple repeats of conventional casts, the priority was obtaining the best possible current estimates despite package motion and a short observation period for each part of the water column. As is usual for this purpose, the ADCPs were operated with 16 large (10 m) bins and short ensembles (1 ping per ensemble; average 1 ping/second). At some stations, the package was held for up to 30 minutes at one or more depths (frequently with repetition), for observation of a dense plume from the Filchner continental shelf. In such cases, package motion and limited observation time were lesser concerns, and good quality ensembles with high spatial resolution were priorities. For stations 27 and 62- 71 four metre bins were used for each WH. This was also the case for stations 72 and 82, with the further alteration that 300 ping ensembles were used.

Plume stations LADCP data

The aim of stations 72 and 82 was to capture the plume of Ice Shelf Water (ISW) originating from the Filchner Ice Shelf Cavity and flowing into the deep Weddell Sea. The CTD package followed the cycle described in the table below. The navigation, temperature and, salinity were logged at each stage. The aim is to analyse the temporal variability of the plume. The reason for choosing to hold the package at 90 m and 180 m above the bottom is so the LADCPs can get a profile for the whole plume.

Stage in cycle Description
1 CTD package lowered to 5m above sea bed
2 CTD raised to 90 m above bottom
3 CTD held at 90 m above for 30 minutes
4 CTD raised up and out of plume
5 CTD lowered to 5 m above sea bed
6 CTD raise to 180 m above sea bed
7 CTD held at 180 m above for 30 minutes
8 CTD raise up out of plume
9 Back to stage 1 and repeat cycle or bring CTD package back to surface

BODC Processing

The data were sent to BODC in Matlab binary .MAT files. The files contained data from the 'upcast', 'downcast' and, 'meancast' for each ADCP. It was decided that only data from the 'downcast' would be transferred as per BODC data banking guidelines. The data was transferred to QXF format using BODC generated Matlab code. Each variable within the original files is assigned a unique BODC parameter code. The parameter code mapping can be seen below.

Matlab Variable Name Description Units BODC Parameter Code Parameter Units Comment
d_samp Depth of profile bin metres DEPHPR01 metres  
sm_dn_i Downcast good / bad data mask dimensionless n/a n/a Used to apply BODC's 'L' flag to data points (originator's marked suspect data)
sn_dn_i Downcast number of sample points per LADCP bin dimensionless NLADCPBN dimensionless  
su_dn_i Downcast east-west velocity by LADCP m s -1 LCEWLW01 cm s -1 Unit conversion needed. LCEWLW01 = 100su_dn_i
su_var_dn_i Downcast east-west velocity variance by LADCP m 2 s -2 SDEWLW01 cm s -1 Variance converted to standard deviation and unit conversion is applied. SDEWLW01 = 100su_var_dn_i 0.5
sv_dn_i Downcast north-south velocity by LADCP m s -1 LCNSLW01 cm s -1 Unit conversion needed. LCNSLW01 = 100sv_dn_i
sv_var_dn_i Downcast north-south velocity variance by LADCP m 2 s -2 SDNSLW01 cm s -1 Variance converted to standard deviation and unit conversion is applied. SDNSLW01 = 100sv_var_dn_i 0.5
sw_dn_i Downcast vertical velocity by LADCP m s -1 n/a n/a Not transferred due to originator's warnings
sw_dn_var_i Downcast vertical velocity variance by LADCP m 2 s -1 n/a n/a Not transferred due to originator's warnings
txy_start_end Profile start and end date, latitude and longitude n/a n/a n/a Information not held in QXF but copied to metadata table

The data were screened using BODC in-house visualisation software and any suspect data points were flagged with the appropriate data quality control flag.


Project Information

AutoSub Under Ice (AUI) Programme

AutoSub was an interdisciplinary Natural Environment Research Council (NERC) thematic programme conceived to investigate the marine environment of floating ice shelves with a view to advancing the understanding of their role in the climate system.

The AUI programme had the following aims:

Following the invitation of outline bids and peer review of fully developed proposals, eight research threads were funded as part of AUI:

Physical Oceanography

Glaciology and Sea Ice

Geology and Geophysics

Biology

The National Oceanography Centre Southampton (NOCS) hosted the AUI programme with ten further institutions collaborating in the project. The project ran from April 2000 until the end of March 2005, with some extensions to projects beyond this date because of research cruise delays. The following cruises were the fieldwork component of the AUI project:

Table 1: Details of the RRS James Clark Ross AUI cruises.

Cruise No. Cruise No. synonyms Dates Areas of study
JR20030218 JR84 28 February 2003 to 4 April 2003 Amundsen Sea, Antarctica
JR20040813 JR106, JR106a, JR106N (North) 10 August 2004 to 30 August 2004 Northeast Greenland Continental Shelf, Greenland
JR20040830 JR106b, JR106S (South) 30 August 2004 to 16 September 2004 Kangerlussuaq Fjord, Greenland
JR20050203 JR97, JR097 3 February 2005 to 11 March 2005 Fimbul Ice Shelf and Weddell Sea, Antarctica . This cruise was redirected from the Filcner-Ronne Ice Shelf to the Fimbul Ice Shelf because of unfavourable sea-ice conditions.

All the cruises utilised the AutoSub autonomous, unmanned and untethered underwater vehicle to collect observations beneath sea-ice and floating ice shelves. AutoSub can be fitted with a range of oceanographic sensors such as:

In addition to use of AutoSub during each cruise measurements were taken from ship. These varied by cruise but included:

The AutoSub project also included numerical modelling work undertaken at University College London, UK.

The project included several firsts including the first along-track observations beneath an ice shelf using an autonomous underwater vehicle. The AutoSub vehicle was developed and enhanced throughout this programme and has now become part of the NERC equipment pool for general use by the scientific community. Further information for each cruise can be found in the respective cruise reports (links in Table 1).


Data Activity or Cruise Information

Cruise

Cruise Name JR20050203 (JR97)
Departure Date 2005-02-03
Arrival Date 2005-03-11
Principal Scientist(s)Keith Nicholls (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