Metadata Report for BODC Series Reference Number 581178

• 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

Problem Reports

No Problem Report Found in the Database

Data Quality Report: Series 581178 (9317-2)

The meter stopped shortly after deployment at 1300, 12 March 1993 after only 47 hours.

High and low precision thermistor values are in very good agreement, the high precision values being retained. Temperatures at the meter depth from a CTD cast, 4 minutes N, 13 minutes E of the mooring and started just after its deployment, do not agree especially well with the thermistor at the start of the series (1.35°C from the CTD, 1.09°C from the thermistor).

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 4/5

Manufacturer's specifications: Meter (recording unit: height 51cm, diameter 12.8cm, vane size 37x100cm; overall: length 137cm, height 75cm) is designed for depths down to 2000m (6000m RCM model 5). It incorporates a spindle which is shackled into 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. Savonius rotor magnetically coupled to an electronic counter - the number of revolutions during the sampling interval giving the average current speed over the interval - starting speed 2cm/s (users find 1.5 to 3cm/s), range 2.5 to 250cm/s, accuracy greater of 1cm/s or 2 per cent.

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 at instant of sampling only) - direction recorded with 0.35° resolution, 5° accuracy (1.5° claimed by MAFF, Lowestoft) for speeds 5 to 100cm/s, 7.5° accuracy for remaining speeds within 2.5 to 200cm/s range, maximum compass tilt (i.e. maximum deviation of the meter from the horizontal at which the meter still registers correctly) is 12° in both pitch and roll axes.

4. Quartz clock, accuracy better than 2sec/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 0.15°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. Bourdon tube pressure sensor (optional) driving a potentiometer - range 0 to 100, 200, 500, 1000 or (RCM4 to 3000psi), (RCM5 to 5000, or 8000psi), lowest calibrated pressure 14.24psi, accuracy 1 per cent of range, resolution 0.1 per cent 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.

Sample duration equals nominal interval between data cycles pre-chosen as 0.5, 1, 2, 5, 10, 15, 20, 30, 60 or 180 minutes. Sample recording order: meter reference number, temperature, (conductivity, pressure if installed), current direction, speed.

Manufacturer's calibration formulae:

Meters (manufactured prior to October 1974) with analogue measurement of speed, i.e. the Savonius rotor drives a potentiometer via a magnetically coupled follower and gearbox (6000 : 1 gear ratio):

speed = 1.5 + 246 * (M/T) cm/s (1)

meters with digital measurement of speed i.e. utilizing an electronic reed switch to count the total number of rotor revolutions during the sampling interval:

speed = 1.5 + 42 * B * (M/T) cm/s (2)

all meters:
direction = 1.5 + 0.349N ° magnetic (3)

where
B is the number of rotor revolutions per count, M (bits) binary is the count over the sampling interval T (sec) and N (bits) binary is the direction reading.

Note:
Data collecting laboratories may calibrate their own meters and so not use the manufacturer's calibration equations.

BODC Current Meter Screening

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as unfeasible values
• Inconsistencies between related information. For example:
  • Depths of meter and sea bed.
  • Times for mooring deployment and for start/end of data series.
  • Length of record or number of data cycles, the cycle interval, the clock error and the period over which accrued.
  • Parameters stated as measured and the parameters actually present in the data cycles.
• Originator's comments on meter/mooring performance and data quality.

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non- oceanographic origin may be tagged with the BODC flag denoting suspect value.

The following types of irregularity, each relying on visual detection in the time series plot, are amongst those which may be flagged as suspect:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities, deemed abnormal, then instead of flagging the individual suspect values, a caution may be documented. Likewise documents will highlight irregularities seen in the current vector scatter plots such as incongruous centre holes, evidence of mooring 'knock-down', abnormal asymmetry in tidally dominated records or gaps as when a range of speeds or directions go unregistered due to meter malfunction.

The term 'knock-down' refers to the situation when the 'drag' exerted on a mooring at high current speeds may cause instruments to tilt beyond the angle at which they are intended to operate. At this point the efficiency of the current sensors to accurately record the flow is reduced.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought, and where necessary, documented. This covers inconsistencies in the following:

• Maximum and minimum values of parameters (spikes excluded).
• The orientation and symmetry of the current vector scatter plot.
• The direction of rotation of the current vectors.
• The approximate amplitude and periodicity of the tidal currents.
• The occurrence of meteorological events and, finally, for series for which no time check was possible, the phase.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

World Ocean Circulation Experiment (WOCE)

The World Ocean Circulation Experiment (WOCE) was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate.

WOCE had two major goals:

• Goal 1. To develop models to predict climate and to collect the data necessary to test them.

• Goal 2. To determine the representativeness of the Goal 1 observations and to deduce cost effective means of determining long-term changes in ocean circulation.

ADOX - Antarctic Deep Outflow Experiment

ADOX formed component SCM6 of WOCE (World Ocean Circulation Experiment), 1993-1994, and entailed an array of current meters. The goal of the experiment was to measure the flow of deep and bottom waters passing eastward from the Enderby Abyssal Plain to the southern Indian Ocean via deep topographic gaps to the northwest and southwest of the Kerguelen Plateau. To this end current meters were placed in the main gap between Crozet and Kerguelen, and supplemented with a mooring in the deep cleft immediately to the northwest of Crozet Island. In addition, two of the moorings in the main Crozet-Kerguelen array were extended upward into the near-surface layers to aid the subsequent SWINDEX (Southwest Indian Ocean Experiment, WOCE component SCM9) investigations into the interactions of the Agulhas and Antarctic Circumpolar Currents.

Two arrays were deployed, consisting of a total of 16 moorings, comprising 57 Aanderaa Recording Current Meters of various types. 46 units were recovered. The major portion of this dataset consists of current records from a linear array of 8 moorings extending across the deep passage between the Crozet Islands and the Kerguelen Plateau. There is an additional current meter record from a single mooring northwest of the Crozet Islands. In all, 32 good records were obtained. Aanderaa current meters with a sampling interval of one hour were employed throughout. All of the instruments recorded speed, direction, and temperature. One instrument recorded pressure (in addition) and another recorded conductivity.

The World Ocean Circulation Experiment took place in the 1990s. The experiment was made up of the following components:

• WOCE component SCM2 (Greenwich Meridian), 1986-1994
• WOCE component SCM3 (South of Tasmania), 1991-1997
• WOCE component SCM4 (West Australian Basin), 1995-1996
• WOCE component SCM6 (ADOX), 1993-1994
• WOCE component SCM7 (Weddell Sea), 1985-1995
• WOCE component SCM9 (SW Indian Ocean), 1993-1995

Data Activity or Cruise Information

Data Activity

CEFAS ADOX Mooring 9317 (1993)

Mooring (46.842°S, 53.338°E) consisted of three current meters at the following depths:

Related Data Activity activities are detailed in Appendix 1

Cruise

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: 9317

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.