Metadata Report for BODC Series Reference Number 1766108

Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
SeaDataNet Quality Flags

Metadata Summary

Data Description

Data Category

Currents -subsurface Eulerian

Instrument Type

Name	Categories
Teledyne RDI 300kHz Workhorse Monitor direct-reading ADCP	current profilers

Instrument Mounting

lowered unmanned submersible

Originating Country

United Kingdom

Originator

Dr Stefan Gary

Originating Organization

Scottish Association for Marine Science

Processing Status

banked

Online delivery of data

Download available - Ocean Data View (ODV) format

Project(s)

Data Identifiers

Originator's Identifier	081DL000
BODC Series Reference	1766108

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm)	2016-06-21 07:49
End Time (yyyy-mm-dd hh:mm)	2016-06-21 08:27
Nominal Cycle Interval	5.0 metres

Spatial Co-ordinates

Latitude	57.07413 N ( 57° 4.4' N )
Longitude	9.33072 W ( 9° 19.8' W )
Positional Uncertainty	0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth	5.0 m
Maximum Sensor or Sampling Depth	915.0 m
Minimum Sensor or Sampling Height	7.28 m
Maximum Sensor or Sampling Height	917.29 m
Sea Floor Depth	922.29 m
Sea Floor Depth Source	DATAHEAD
Sensor or Sampling Distribution	Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum	Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum	Instantaneous - Depth measured below water line or instantaneous water body surface

Parameters

BODC CODE	Rank	Units	Title
ACYCAA01	1	Dimensionless	Sequence number
DEPHPR01	1	Metres	Depth (spatial coordinate) relative to water surface in the water body by profiling pressure sensor and conversion to seawater depth using UNESCO algorithm
LCEWLW01	1	Centimetres per second	Eastward velocity of water current (Eulerian measurement) in the water body by lowered acoustic doppler current profiler (ADCP)
LCNSLW01	1	Centimetres per second	Northward velocity of water current (Eulerian measurement) 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

RRS Discovery DY052 LADCP instrument description

LADCP deployments were carried out using the instrumentation detailed below.

The ADCP were attached to a SeaBird 9plus CTD frame during each deployment.

Instrument	Serial #	CTD casts
TRDI WHM 300kHz Workhorse ADCP	4275	1-50
TRDI WHM 300kHz Workhorse ADCP	13400	51-73
TRDI WHM 300kHz Workhorse ADCP	13399	74-89

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.

RRS Discovery DY052 LADCP: Processing undertaken by BODC

The data arrived at BODC in 89 Matlab files. The files contained u, v and z data collected from 89 LADCP deployments undertaken throughout the DY052 cruise. The data were reformatted to BODC's internal NetCDF format and the following table shows the mapping of variables within the .mat file to the appropriate BODC parameter codes:

Originator's Variable	Units	Description	BODC Parameter Code	Units	Comment
u(eastward velocity)	m/s	Eastward current velocity (Eulerian) in the water body by lowered acoustic doppler current profiler (ADCP))	LCEWLW01	cm/s	Units converted from m/s to cm/s by multiplying by 100
v (northward velocity)	m/s	Northward current velocity (Eulerian) in the water body by lowered acoustic doppler current profiler (ADCP)	LCNSLW01	cm/s	Units converted from m/s to cm/s by multiplying by 100
z(depth)	m	Depth below surface of the water body	ADEPZZ01	m	-

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.

RRS Discovery DY052 Originator's LADCP data processing

Sampling Strategy

Lowered Acoustic Doppler Current Profiler (LADCP) data were gathered during the RRS Discovery DY052 cruise which occupied the Extended Ellett Line.

Data Processing

The data collected by the instrument were downloaded after each cast and stored as RDI binary files. The data were then processed following the cruise using the IX.8 version of software provided Lamont- Doherty Earth Observatory (LDEO) which calculates velocities using an inverse method.

Please refer to Thurnherr (2014) and cruise report for a more detailed processing methodology. However, please be aware that this processing guide is for software versions IX.7 to IX.10 only, and changes have been made between versions which have the potential for significantly changing the solutions.

More detailed processing was then undertaken by the originator during the cruise using Matlab scripts. The processing steps are listed below:

processing without any auxiliary data
merging with CTD and GPS data
processing with constraint from VMADCP data (except for casts 1, 61, 62, 66 and 70-72 which had insufficient VMADCP data to create a constraint)
visual inspection to compare with VMADCP data (top of the profile)
checking that bottom-tracking velocities match those of the water track
checking the performance of the 4 beams
comparing profiles from the up and down casts to check that they are both complete
synchronisation of the real-time clock of the LADCP with the ship's GPS clock if it was more than a few seconds in error

The raw RDI binary files and the ASCII data files created before Matlab processing began are available on request from BODC.

References

Thurnherr, A.M., (2014). How to Process LADCP Data with the LDEO Software (versions IX.7 - IX.10).

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name	DY052
Departure Date	2016-06-07
Arrival Date	2016-06-24
Principal Scientist(s)	Stefan F Gary (Scottish Association for Marine Science)
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