Metadata Report for BODC Series Reference Number 906908


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Aanderaa RCM 7/8 Recording Current Meter  current meters
Instrument Mounting subsurface mooring
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 SB_LM_A#1/CM6750
BODC Series Reference 906908
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2005-09-06 12:30
End Time (yyyy-mm-dd hh:mm) 2006-08-23 09:30
Nominal Cycle Interval 3600.0 seconds
 

Spatial Co-ordinates

Latitude 59.56617 N ( 59° 34.0' N )
Longitude 41.55067 W ( 41° 33.0' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 1774.0 m
Maximum Sensor Depth 1774.0 m
Minimum Sensor Height 315.0 m
Maximum Sensor Height 315.0 m
Sea Floor Depth 2089.0 m
Sensor Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor Depth Datum Approximate - Depth is only approximate
Sea Floor Depth Datum Approximate - Depth is only approximate
 

Parameters

BODC CODE Rank Units Short Title Title
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
CNCLCCI1 1 Siemens per metre Cond_ind_cal Electrical conductivity of the water body by in-situ conductivity cell and calibration against independent measurements
LCDAEL01 1 Degrees True CurrDir Current direction (Eulerian) in the water body by in-situ current meter and correction to true North
LCEWEL01 1 Centimetres per second CurrVelE_CM Eastward current velocity (Eulerian) in the water body by in-situ current meter
LCNSEL01 1 Centimetres per second CurrVelN_CM Northward current velocity (Eulerian) in the water body by in-situ current meter
LCSAEL01 1 Centimetres per second CurrSpd_CM Current speed (Eulerian) in the water body by in-situ current meter
PRCLCCI1 1 Decibars Pres_ind_cal Pressure (measured variable) exerted by the water body by semi-fixed in-situ pressure sensor and corrected to read zero at sea level using independent measurements
PSCLCCI1 1 Dimensionless PSal_ind_cal Practical salinity of the water body by in-situ conductivity cell and computation using UNESCO 1983 algorithm and calibration against independent measurements
TMCLCCI1 1 Degrees Celsius Temp_ind_cal Temperature of the water body by in-situ thermometer and calibration against independent measurements
 

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

RAPID Cape Farewell data quality document

Salinity showed an upward drift for the first few days in most records, which is thought to be entirely instrumental behaviour, and was deemed noisy by the originators. Care should be taken when using these data.

RAPID - Cape Farewell data quality report

Current speed values of 1.1 have been flagged suspect as this is indicative of rotor stall, a common problem with RCM7/8s. Corresponding data in the E-W and N-S velocity components have also been flagged suspect.


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

Aanderaa Recording Current Meter Model 7/8

Manufacturer's specifications: recording unit height 49.5cm (RCM8 52.0cm), diameter 12.8cm, vane size 48.5x50.0cm. Meter is designed for depths down to 2000m (RCM8 6000m). It incorporates a spindle which is shackled to the mooring line. The meter is attached to the spindle through a gimbal mounting which permits a maximum 27° deviation of the spindle from the vertical, the meter still remaining horizontal.

Meter comprises :

  1. Paddle wheel rotor magnetically coupled to an electronic counter

  2. Vane, which aligns instrument with current flow, has a balance weight ensuring static balance and tail fins to ensure dynamic balance in flows up to 250cm/s.

  3. Magnetic compass (needle is clamped to potentiometer ring) - direction recorded with 0.35° resolution, 5° accuracy for speeds 5 to 100cm/s, 7.5° accuracy for remaining speeds within 2.5 to 200cm/s range.

  4. Quartz clock, accuracy better than 2 sec/day within temperature range 0 to 20°C.

  5. Thermistor (temperature sensor), standard range -2.46 to 21.48°C (max on high range 36.04°C), accuracy 0.05°C, resolution 0.1 per cent of range, 63 per cent response time 12sec.

  6. Inductive cell conductivity sensor (optional), range 0 to 70mmho/cm standard resolution 0.1 per cent of range.

  7. Silicon piezoresistive bridge, standard range 0 to 3000 psi (RCM8 to 9000 psi), resolution 0.1% of range.

  8. Self balancing potentiometer which converts the output from each sensor into a 10 bit binary number for storage on magnetic tape.

  9. Associated electronics.

A built-in clock triggers the instrument at preset intervals and up to six channels are sampled in sequence. Channel 1 is a fixed reference reading for control purposes and data identification. Channels 2, 3 and 4 represent measurement of temperature, conductivity and pressure. Channels 5 and 6 represent the VECTOR AVERAGED current speed and direction since the previous triggering of the instrument. The number of rotor revolutions and the direction is sampled every 12 seconds and broken into North and East components. Successive components are added and recorded as speed and direction. For recording intervals longer than 10 minutes, speed and direction are sampled 1/50th of recording interval.

It has become common practice in some laboratories to deploy these meters as temperature and conductivity loggers without current measuring capabilities.

The following link will provide the manufacturer specifications:

Manufacturer specifications

RAPID - Cape Farewell current meter data processing notes

This document outlines the procedures undertaken to process and quality assure current meter data collected to the east of Cape Farewell, Greenland, as part of the RAPID programme.

Originator's processing

The raw data are downloaded from the instrument and converted to ASCII format. The data are then converted to PSTAR format.

Calculating calibration coefficients

Manufacturers calibrations are applied to the current speed and direction channels.

Two sets of calibration coefficients were employed in the calibration of the pressure, temperature and conductivity data. The first set was obtained either from the manufacturer's calibration coefficients or from the calibration laboratory at the National Oceanography Centre, Southampton (NOCS), hereinafter called laboratory calibrations. The second set, called in-situ calibrations, was obtained by a comparison with CTD data taken on cruise D309. The current meters were strapped to the CTD frame and a full depth CTD cast performed. CTD data obtained during the cast bottle stops were compared to that from the current meter and coefficients derived by fitting a cubic polynomial to the data of the form:

y = A + Bx + Cx 2 + Dx 3

where A,B,C,D are the coefficients, x is the uncalibrated data and y is the calibrated data.

Both sets of calibration coefficients were employed in converting raw data to physical measurements. Where available, the in-situ temperature and conductivity coefficients were deemed superior as they provided a homogeneous data set.

Data processing

During the conversion from ASCII to PSTAR format the data are calibrated and corrected for magnetic variation. Current velocity components are then derived. Salinity is calculated using the in-situ temperature and conductivity data where available. The pressure for the salinity calculation is chosen on a per instrument basis and is whichever of the two calibration sets that most closely agree with the planned instrument depth/pressure.

The Aanderaa RCM7/8 instruments recorded data throughout each hour (20 samples at 3 minute intervals). Therefore the timestamp of the measurement was selected to be the mid-hour mark. The Aanderaa RCM11 instruments record a burst of measurements just before each hour and each half hour and these were the times assigned to the data measurements.

Quality control

Data were visually inspected for out-lying data and instrument electrical spikes removed.

BODC processing

Data are received after quality checks have been made and calibrations have been applied. The data files are submitted in PSTAR format as one file per instrument.

Once the submitted data files are safely archived, the data undergo standard reformatting and banking procedures:

The following is a summary of what calibrations (laboratory and in-situ) were supplied in which series.

Parameters Series identifier
Laboratory and in-situ calibrated channels 906980, 906921*, 906933, 907045, 906957*, 906969*, 906970*, 906982*, 906994*, 907008*, 907021*, 907033*, 907057*, 907069, 907070*, 907082, 907101*, 907113, 907125*, 907137*, 907149*, 907162, 907174
In-situ calibrated channels only 906980, 906945, 907094
Laboratory calibrated channels only 907150, 907186, 907198, 907205, 907217

*Only contained laboratory calibrated temperature and pressure.

Parameter rationalisation and mapping

The originator expressed a preference for in-situ over laboratory calibrated channels, so where both in-situ and laboratory calibrated channels were present, the laboratory calibrated channels were dropped from the series. Where in-situ calibrated channels were not available, the laboratory calibrated channels were retained.

The following describes the parameters contained in the series and their mapping to BODC parameter codes. Some parameters e.g. current velocities, were not supplied in every file. Where not supplied and applicable, these channels were calculated by BODC. See parameter derivation section below.

Identifier Unit Definition BODC parameter code Units Unit conversion Comments
time seconds Time in seconds from start of year AADYAA01/AAFDZZ01 days - -
pres1/press1/press db Pressure from lab calibrations PRCLCCL1 db - Laboratory calibration.
pres2/press2 db Pressure from in-situ calibrations PRCLCCI1 db - In-situ calibration.
cond1 mmho/cm Conductivity CNCLCCL1 S/m /10 Laboratory calibration.
cond2 mmho/cm Conductivity CNCLCCI1 S/m /10 In-situ calibration.
temp1/temp °C Temperature (IPTS-90) TMCLCCL1 °C - Laboratory calibration.
temp2 °C Temperature (IPTS-90) TMCLCCI1 °C - In-situ calibration.
dir/dirn/dirmag degrees True direction LCDAEL01 degrees - Transferred
dirnorm degrees Direction on plane tilted 32 degrees east from true north - - - Not transferred
speed/spd cm/s Current speed LCSAEL01 cm/s - Transferred
east cm/s Eastward current velocity LCEWEL01 cm/s - If present, transferred
north cm/s Northward current velocity LCNSEL01 cm/s - If present, transferred
v122 cm/s Eastward current velocity on plane tilted 32 degrees east from true north - - - Not transferred
v022 cm/s Northward current velocity on plane tilted 32 degrees east from true north - - - Not transferred
sal83 psu Salinity calculated using in-situ calibrated pressure, temperature and conductivity and UNESCO 1983. PSCLCCI1 dimensionless - If present, transferred
potemp °C Potential temperature (IPTS-90) - - - Not transferred
sal183 psu Salinity - - - Not transferred

Parameter derivation

The following describes the parameters derived by BODC and their mapping to BODC parameter codes. These parameters were only derived by BODC if they were not supplied by the originators.

BODC parameter code Units Variables Definition Units Equation Comments
PSCLCCL1 dimensionless PRCLCCL1
TMCLCCL1
CNCLCCL1
Pressure
Temperature
Conductivity
decibars
°C
S/m
UNESCO 1983 polynomial for salinity Salinity calculated from laboratory calibrated pressure, temperature and conductivity
PSCLCCI1 dimensionless PRCLCCI1
TMCLCCI1
CNCLCCI1
Pressure
Temperature
Conductivity
decibars
°C
S/m
UNESCO 1983 polynomial for salinity Salinity calculated from in-situ calibrated pressure, temperature and conductivity
LCEWEL01 cm/s LCSAEL01 LCDAEL01 Current speed and true direction cm/s
degrees
speed*sin(direction) Eastward current velocity
LCNSEL01 cm/s LCSAEL01 LCDAEL01 Current speed and true direction cm/s
degrees
speed*cos(direction) Northward current velocity

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

Data Activity

Start Date (yyyy-mm-dd) 2005-09-06
End Date (yyyy-mm-dd) 2006-08-23
Organization Undertaking ActivityNational Oceanography Centre, Southampton
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierSB_LM_A#1
Platform Categorysubsurface mooring

RAPID Moored Instrument Rig SB_LM_A#1

This rig was deployed as part of the current meter array to the east of Cape Farewell, Greenland, a component of the RAPID programme.

Deployment cruise RRS Discovery cruise D298
Recovery cruise RRS Discovery cruise D309-310

The rig was anchored by 1200 kg of steel chain bundled together with 5/8" galvanised long link chain. Buoyancy was provided by 17 inch glass spheres attached to the mooring line in groups over the height of the mooring and a 48 inch steel sphere attached at the top of the mooring.

Instruments deployed on the rig

Depth Instrument
98 m *Sea-Bird SBE16 SEACAT
316 m *Aanderaa RCM8 current meter (#12691)
916 m *Aanderaa RCM8 current meter (#12692)
1320 m Aanderaa RCM7 current meter (#11678)
1774 m Aanderaa RCM8 current meter (#6750)
1978 m Aanderaa RCM11 current meter (#383)

*These instruments belong to IFREMER

Other Series linked to this Data Activity - 906921 906890

Cruise

Cruise Name D298
Departure Date 2005-08-23
Arrival Date 2005-09-25
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