Metadata Report for BODC Series Reference Number 604751


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 Bill Turrell
Originating Organization Fisheries Research Services Aberdeen Marine Laboratory (now Marine Scotland Aberdeen Marine Laboratory)
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier 681/2
BODC Series Reference 604751
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2002-06-05 13:50
End Time (yyyy-mm-dd hh:mm) 2002-09-24 08:10
Nominal Cycle Interval 1200.0 seconds
 

Spatial Co-ordinates

Latitude 56.25050 N ( 56° 15.0' N )
Longitude 1.50200 W ( 1° 30.1' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor Depth 40.0 m
Maximum Sensor Depth 40.0 m
Minimum Sensor Height 15.0 m
Maximum Sensor Height 15.0 m
Sea Floor Depth 55.0 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 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 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)
LCDAEL01 1 Degrees True CurrDir Current direction (Eulerian) in the water body by in-situ current meter and correction to true North
LCSAEL01 1 Centimetres per second CurrSpd_CM Current speed (Eulerian) in the water body by in-situ current meter
PSALPR01 1 Dimensionless P_sal Practical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPPR01 1 Degrees Celsius Temp Temperature of the water body
 

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

Salinity shows very high variablity around cycles 5480-6200, with an overall increase of ~0.3 across this region. There is also a general decline in salinity from around cycle 6600 to the end of the series which is likely to be a result of biofouling. No flags have been added to the data as it is impossible to identify a point at which the decline in data quality begins. However, these data should be treated with caution.

An odd circular feature appears on velocity scatter plots. FRS have stated that this may have been due to the rotor sticking.


Data Access Policy

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."


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

BODC Processing

Data were received by BODC in ASCII format files. This series was reformatted to the internal QXF format using BODC transfer function 325. The following table shows how the variables within the file were mapped to the appropriate BODC parameter codes.

Original parameter name Original Units Description BODC Parameter Code BODC Units Comments
Time DD/MM/YYYY HH:MI date and time AADYAA01 and AAFDZZ01 day number and day fraction GMT Conversion by transfer
u + v cm/s Eastward and northward current velocity LCDAEL01 (direction) and LCSAEL01 (speed) °, cm/s Converted by transfer to current direction (Eulerian) in the water column by in-situ current meter and correction to true North, and current speed (Eulerian) in the water column by in-situ current meter
T degrees Celsius Temperature TEMPPR01 degrees Celsius  
S dimensionless Salinity PSALPR01 dimensionless  

Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO. Any data considered as suspect were flagged 'M'. Flags from the originator marking suspect data were retained during transfer and flagged 'L'.

Originator's Data Processing

Sampling Strategy

The Aanderaa RCM 7 current meters deployed at Marr Bank had sampling frequencies of 3 readings per hour. The instruments included temperature and conductivity sensors.

Data Processing

DAF applied the standard manufacturers' calibrations to all current, temperature and salinity data, and produced ASCII files for submission to BODC. Data files were named according to the mooring code (681) and the instrument number (1 or 2). The RCM7 data files (6811/6812) contained eastward and northward velocities, and temperature. Salinity data were provided in a separate file (append s).


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 2002-06-05
End Date (yyyy-mm-dd) 2002-09-24
Organization Undertaking ActivityFisheries Research Services Aberdeen Marine Laboratory (now Marine Scotland Aberdeen Marine Laboratory)
Country of OrganizationUnited Kingdom
Originator's Data Activity Identifier681
Platform Categorysubsurface mooring

DAF Current Meter mooring, Marr Bank

The mooring was located at 56° 15.03' N, 001° 30.12' W in a nominal water depth of 55 m.

The mooring was deployed on 05 June 2002 by the Department of Agriculture and Fisheries (DAF, now known as Marine Scotland Aberdeen Marine Laboratory) on cruise FRV Clupea 0902C (04 June 2002-24 June 2002), recovered on 24 September 2002, and consisted of the following instruments.

Instrument type Serial Number Deployment start Deployment end Instrument depth (m) Comments
Aanderaa RCM 7 12164 2002-06-05 2002-09-24 19  
Aanderaa RCM 7 8592 2002-06-05 2002-09-24 40 Possible sticking of current meter rotor

Other Series linked to this Data Activity - 604738

Cruise

Cruise Name 0902C
Departure Date 2002-06-04
Arrival Date 2002-06-24
Principal Scientist(s)Simon Greenstreet (Fisheries Research Services Aberdeen Marine Laboratory)
Ship FRV Clupea

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