Metadata Report for BODC Series Reference Number 1722640

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

Prof Penny Holliday

Originating Organization

National Oceanography Centre, Southampton

Processing Status

QC in progress

Online delivery of data

Download not available

Project(s)

Data Identifiers

Originator's Identifier	LADCP_079
BODC Series Reference	1722640

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm)	2015-06-15 09:20
End Time (yyyy-mm-dd hh:mm)	-
Nominal Cycle Interval	5.0 decibars

Spatial Co-ordinates

Latitude	56.73322 N ( 56° 44.0' N )
Longitude	7.00094 W ( 7° 0.1' W )
Positional Uncertainty	0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth	5.0 m
Maximum Sensor or Sampling Depth	125.0 m
Minimum Sensor or Sampling Height	14.0 m
Maximum Sensor or Sampling Height	134.0 m
Sea Floor Depth	139.0 m
Sea Floor Depth Source	CTDDATA
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	Approximate - Depth is only approximate
Sea Floor Depth Datum	Approximate - Depth is only approximate

Parameters

No Parameters for BODC Reference Number = 1722640

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 Report

All casts were processed, although it was noted that casts shallower than 100-200 m often seemed to have problems, usually characterised as giving a profile that was significantly deeper than the true water depth. It is assumed this was due to confusing reflections at the seabed, and recommend that those profiles not be used (Casts 35, 37, 46, 47, 68-75, 79-81, 83). For more information see the cruise report page 35.

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	Teledyne RDI high-power Workhorse 300kHz	15288	-	LDEO unit, downward looking

One Teledyne RDI Workhorse 300kHz ADCP was mounted on the Sea-Bird 9 11 plus CTD frame pointing downward (downlooker).

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.

BODC Processing

LDEO processed data were provided by the originator in Matlab and ASCII formats. The LDEO processed data in ASCII format were converted into BODC internal format after discussion with the originator. All data provided were from the downward looking RDI 300 kHz Workhorse ADCP which was in operation at the time. The following table shows how the variables within the ASCII files were mapped to appropriate BODC parameter codes:

Originator's Parameter Name	Units	Description	BODC Parameter Code	Units	Comments
z	m	Depth of LADCP bin	ADEPZZ01	m	-
u	m s^-1	Eastward velocity	LCEWLW01	cm s^-1	Units converted from m s^-1 to cm s^-1 by multiplying by 100.
v	m s^-1	Northward velocity	LCNSLW01	cm s^-1	Units converted from m s^-1 to cm s^-1 by multiplying by 100.
ev	m s^-1	Uncertainty estimates of LADCP velocity profile	ERRVLDCP	cm s^-1	Units converted from m s^-1 to cm s^-1 by multiplying by 100.

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 the more complex LDEO processed data are available on request in Matlab format as well as the unprocessed raw LADCP files.

Originator's Data Processing

Sampling Strategy

A total of 84 LADCP profiles were collected at all CTD stations in order to derive full-depth profiles of ocean velocity, as well as profiles of finestructure vertical shear.

Data processing

Preliminary shipboard processing of the LADCP data was carried out with the LDEO IX LADCP processing software using averaged one Hz ascii CTD data in order to correct the LADCP data for depth and sound speed.

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.

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	DY031
Departure Date	2015-05-29
Arrival Date	2015-06-17
Principal Scientist(s)	N Penny Holliday (National Oceanography Centre, Southampton)
Ship	RRS Discovery

Complete Cruise Metadata Report is available here

Fixed Station Information

Station Name	Ellett Line/Extended Ellett Line Station 7G
Category	Offshore location
Latitude	56° 43.98' N
Longitude	7° 0.00' W
Water depth below MSL	145.0 m

Ellett Line/Extended Ellett Line: Station 7G

Station 7G is one of the fixed CTD stations, which together form The Extended Ellett Line. The line lies between Iceland and the Sound of Mull (Scotland) crossing the Iceland Basin and Rockall Trough via the outcrop of Rockall. As part of this initiative, CTD dips, together with associated discrete sampling of the water column, have typically been carried out annually at this station since September 1996.

Prior to September 1996, Station 7G was part of a shorter repeated survey section, consisting of 35 fixed stations, known as The Ellett Line (originally termed the Anton Dohrn Seamount Section). This line incorporated those stations across the Rockall Trough and Scottish shelf between Rockall and the Sound of Mull and was visited at regular intervals (usually at least once a year) between 1975 and January 1996. During this period Station 7G was also referred to as Station C5.

Related Fixed Station activities are detailed in Appendix 1

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