Metadata Report for BODC Series Reference Number 808895


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Teledyne RDI 150kHz Narrowband Vessel-Mounted ADCP  current profilers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Sheldon Bacon
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) Rapid Climate Change Programme
RAPID-Bacon
 

Data Identifiers

Originator's Identifier ADP30909
BODC Series Reference 808895
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2006-08-25 20:03
End Time (yyyy-mm-dd hh:mm) 2006-08-26 20:01
Nominal Cycle Interval 120.0 seconds
 

Spatial Co-ordinates

Start Latitude 59.06250 N ( 59° 3.8' N )
End Latitude 59.70787 N ( 59° 42.5' N )
Start Longitude 39.88883 W ( 39° 53.3' W )
End Longitude 42.39137 W ( 42° 23.5' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor Depth 11.0 m
Maximum Sensor Depth 391.0 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
DBINAA01 0 Metres BinDep Depth below sea surface (ADCP bin)
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
ALATTR01 1 Degrees Lat_TrimbleGPS Latitude north (WGS84) by Trimble GPS
ALONTR01 1 Degrees Lon_TrimbleGPS Longitude east (WGS84) by Trimble GPS
APEWTR01 2 Centimetres per second PlatformVelE_GPS Eastward velocity (over ground) of measurement platform by Trimble GPS
APNSTR01 2 Centimetres per second PlatformVelN_GPS Northward velocity (over ground) of measurement platform by Trimble GPS
ASAMAS01 2 Decibels ADCPSA Signal return amplitude from the water body by shipborne acoustic doppler current profiler (ADCP)
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)
LERRAS01 2 Centimetres per second ADCPER Current velocity error in the water body by shipborne acoustic doppler current profiler (ADCP)
LREWAS01 2 Centimetres per second RelCurrVelE_ADCP Eastward current velocity (relative to moving platform) in the water body by shipborne acoustic doppler current profiler (ADCP)
LRNSAS01 2 Centimetres per second RelCurrVelN_ADCP Northward current velocity (relative to moving platform) in the water body by shipborne acoustic doppler current profiler (ADCP)
LRZAAS01 2 Centimetres per second ADCPVC Upward current velocity in the water body by shipborne acoustic doppler current profiler (ADCP)
PCGDAP01 2 Percent Percent_Good_(ADCP) Acceptable proportion of signal returns by 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

The channels LERRAS01, LRZAAS01, LCEWAS01, LCNSAS01 are noisy. Although no specific values are flagged the data should be used with caution due to the level of noise.


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 150kHz Narrow Band Acoustic Doppler Current Profiler

Specifications

Water velocity measurements relative to the ADCP
Accuracy (long term) 0.5 % of measured velocity ± 0.5 cm/s
Statistical uncertainty for one ping (cm/s) Depth cell length of 4, 8, 16 m = 26, 13, 6.5 respectively (for horizontal velocities using the standard transducer)
Ping rate (pings per second) 2 (100 pings averaged in ADCP)
Maximum profiling range (meters) 290
Minimum range to start of first depth cell (meters) 4
Number of depth cells 8 to 128
Velocity range ± 0.01 to 9.5 m/s (horizontal)
Velocity resolution (cm/s) 0.25 or 0.125
Velocity measurements relative to the bottom and measurement of bottom depth
Accuracy 0.5% of measured velocity ± 0.5 cm/s
Statistical uncertainty of one ping (percent of measured velocity) 3.5 (for horizontal velocities using the standard transducer)
Ping rate (pings per second) 0.9 (100 pings averaged in ADCP)
Depth range 290 (the maximum depth range can be up to 1.5 times greater than specified)
Bottom depth resolution (meters) 4
Velocity range ± 0.01 to 9.5 m/s (horizontal)
Velocity resolution (cm/s) 0.25 or 0.125
Measurement of echo intensity
Accuracy (with temperature correction) Before calibration : ± 8 dB, After calibration: ± 3 dB
Statistical uncertainty for one ping Approximately ± 5 dB
Ping rate (pings per second) 2 (100 pings averaged in ADCP)
Profiling range (meters less than for water velocity measurement) 64
Number of depth cells 8 to 128
Dynamic range 80 dB
Resolution 0.45 dB typical (temperature/system dependent)
Data communication
Interface Modified RS-232/422 serial at baud rates of 300-19,200
Data format Binary (8-bit) or ASCII (76-character) lines separated by a carriage return/line feed.
Data storage capacity 2 MB (standard); expandable to 40 MB in 1 and/or 2 MB increments
Power requirements
ADCP electronics Voltage range (VDC) 6-12; Standby current (amps) 0.0002; Operate current (amps) 0.24; Peak current (amps) 0.5
transmit and EPROM recorder Voltage range (VDC) 20-40; Standby current (amps) 0.0001; Operate current (amps) 0.10; Peak current (amps) 2.0
CTD sensors Voltage range (VDC) 12-20; Standby current (amps) 0.0001; Operate current (amps) 0.022; Peak current (amps) 0.05
Temperature sensor
Accuracy ± 0.2°C
Time constant Approximately 2 minutes
Range -5° to 45°C
Resolution 0.012°C
Environmental
Operating temperature -5°C to 40°C
Humidity Must be non-condensing
Depth capability 35 meters (transducer only)
Physical characteristics
Weight in air 67.6 kg
Weight in water 25.0
Diameter 45.9 cm
Length 141.4 cm

RAPID cruise D309-310 150 kHz Shipboard ADCP data: BODC processing

The data were provided to BODC in PStar format with the files named as adp309##.abs, where ## is the daily file number (from 1 -17). The files are transferred to a netcdf format by following BODC transfer procedures. The transfer involves mapping the originator's variables to unique BODC parameter codes. The parameter mapping can be seen below.

Originator's variable Description Units Parameter Code Units Comments
lat Latitude (+ve N) Degrees ALATTR01 Degrees -
lon Longitude (+ve E) Degrees ALONTE01 Degrees -
evelcal Eastward velocity cms -1 LREWAS01 cms -1 Relative to ship
nvelcal Northward velocity cms -1 LRNSAS01 cms -1 Relative to ship
ve Ship's eastward velocity cms -1 APEWTR01 cms -1 -
vn Ship's northward velocity cms -1 APNSTR01 cms -1 -
absve Absolute eastward velocity cms -1 LCEWAS01 cms -1 -
absvn Absolute northward velocity cms -1 LCNSAS01 cms -1 -
velvert Upward velocity cms -1 LRZAAS01 cms -1 -
velerr Velocity error cms -1 LERRAS01 cms -1 -
amp1 Amplitude decibar ASAMAS01 decibar -
good Percentage good signal return % PCGDAP01 % -

Detailed metadata and documentation are linked to the data.

Data quality procedures are then performed on the files using BODC generated in house visualisation tools.

RAPID cruise D309-310 150 kHz Shipboard ADCP data: Originator's processing

A 150 kHz ADCP is hull mounted 1.75 m to port of the keel and 33 m aft of the bow at an approximate depth of 5 m.

Navigation data is usually obtained from a BestNav system which uses a hierarchy of GPS devices to constantly give the most accurate positional data. However, the BestNav system was not used during the cruise as it was judged to be giving questionable output. A high quality navigation file was obtained from a GPS Trimble 4000 system with an Ashtech G12 system providing differential corrections.

Data from the ADCP were logged using RDI Data Acquisition Software (DAS) version 2.48 with profiler firmware 17.20. The instrument sampled over 120 second intervals with 96 bins of 4 m thickness, pulse length 4 m and a blank beyond transmit of 4 m. At the beginning of the cruise, the ADCP was switched on to bottom track mode over the continental shelf to enable calibration of the instrument. This resulted in the following calibration being applied:

tanØ = 0.0153 (±s.d = 0.0060),Ø = 0.8740 o and A = 0.9983 (±s.d = 0.0057)

Where Ø is the misalignment angle and A is the Scaling Factor.

The ADCP had been refitted while RRS Discovery was in dry dock to a heading offset of approximately 45 o . This offset is accounted for in the DAS software. On previous cruises the ADCP PC clock had been synchronised with the ship's master clock but this was not the case on this cruise. This resulted in a steady drift of approximately 4 s a day. Time checks were made every 24 hours and the time offset was accounted for in the subsequent Matlab processing files to give the correct time in the output files. In addition, all velocities where the percentage of good signal return variable was 25% or less are deleted by the ADCP Matlab software.

More detailed information can be found in the D309-310 cruise report


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.


RAPID - Cape Farewell and Eirik Ridge: Interannual to Millennial Thermohaline Circulation Variability

This project was funded under the NERC Rapid Climate Change Programme, grant number NER/T/S/2002/00453. Dr. Sheldon Bacon (Southampton Oceanography Centre) was the Principal Investigator, with co-Investigators from the University of Southampton, Prof. D. A. Stow and Dr. E. J. Rohling. The project started in December 2003 and ended in November 2008.

The project used a combination of hydrography and palaeoceanography measurements to determine the spectrum of variability of the Deep Western Boundary Current, on timescales from days to millennia. The project focused on deglacial to Holocene variability; in particular, seeking to characterise the onset and endings of three cold periods: the Younger Dryas (YD; 12.5-11.5 ka BP), the ~8.2 ka event, and the Little Ice Age (LIA; 16th-19th century AD).

The objectives of the project included:

Most of the fieldwork was carried out on 2 cruises in the Cape Farewell and Irminger Sea vicinity:

Cruise Start End Comments
D298 2008-08-23 2005-09-05 Work included mooring deployments, sediment coring, sampling for isotopes and CTD casts
D309-310 2006-08-18 2006-09-05 Work included mooring turn-arounds and CTD casts.

Data Activity or Cruise Information

Cruise

Cruise Name D309-310
Departure Date 2006-08-18
Arrival Date 2006-09-05
Principal Scientist(s)Sheldon Bacon (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