Metadata Report for BODC Series Reference Number 33816

• 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 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 Current Meter/Pressure Recorder

The instrument comprises a bottom mounted rig which utilises a Digiquartz sensor and an Aanderaa current meter (with the adaption of a small vane replacing the normal vane) both interfaced into a modified Aanderaa current meter logger. Current meter speed and absolute pressure count are integrated over a pre-selected period (usually 10 or 15 minutes) and sampled by the logger at the same pre-selected time interval, together with spot readings of vane direction, temperature, elapsed time and rig orientation. The pressure sensor consists of a convoluted bellows linked to a 40kHz quartz crystal resonator coupled by piezoelectric action to an electronic resonator. A quartz crystal clock is used for controlling the sampling interval.

The data are recorded on magnetic tape as 10 bit binary words in serial form with the frequency count from the pressure sensor stored as most and last significant counts. The pressure sensor pack, containing the Digiquartz type 2-300a quartz crystal pressure transducer but no temperature transducer, is mounted approximately 1m above the rig base, with the current meter 0.7m above the base. The rig is 1.5m in height and the base is formed by a tripod with legs of length approximately 0.7m. The current meter/pressure recorder is usually deployed using a U-shaped mooring (i.e. buoy or pellet float to wire rope to tide gauge to ground line to anchor to wire rope to buoy), but W-shaped moorings are used in conjunction with either current meters or thermistor chains. A W-shaped mooring comprises pellet float to pellet line to sub-surface buoy to current meter or thermistor line to anchor weight to ground line to tide gauge to ground line to anchor weight to wire rope to surface buoy.

IOS Calibration and Data Processing of Off-Shore Tide Gauge Data

Calibration of pressure/frequency sensors and thermistors are carried out using the facilities and staff at I.O.S. Bidston with the exception of pre 1975 pressure/frequency sensors, which were calibrated in the pressure chamber at I.O.S. Wormley.

The data are copied from the logger magnetic tape to 9 track magnetic tape and disk. The data are either listed or plotted as an initial check. A program is then used to check the data from the temperature sensor channels, calculate and plot the temperature values and store them (if temperature sensor channels are available).

A second program performs a similar function for the pressure sensor channel, using the pressure frequency coefficient to convert each pressure frequency to the frequency at the reference temperature and calculating the pressures using the pressure frequency calibration. The data values, generally at 15 minute intervals, but occasionally at 10 minute intervals, of pressure are then plotted and stored. If waterhead is required, it may be computed by subtracting atmospheric pressure and applying the hydrostatic relation:-

H = P / ( d * g )
H = waterhead (cm)
P = pressure (0.01 mb)
d = density (kg/m3)
g = gravitational acceleration (m/s2)

Station 53 (Northern North Sea) Data Processing Notes

Clock gained 69 seconds over 58 days, 2.75 hours; the cycle interval and time values have been corrected.

Instrument characteristics and calibration factors

To convert pressure to elevation the following values should be used:

A current meter was also deployed on this mooring.

Project Information

1976 Joint North Sea Data Acquisition Project (JONSDAP 76)

This was the third phase of the cooperative data collection programme JONSDAP, begun in 1970 by the countries bordering the North Sea. It consisted of two intensive measurement programmes:

• FLEX (the Fladen Ground Experiment)studied the development of the thermocline and the dynamics of the plankton bloom in spring in relation to the physical, chemical and biological environment. Measurements were concentrated in a square of side 100km for 100 days from March to June.
• INOUT was concerned with the general circulation of the North Sea and the storm surge problem. Currents flowing into and out of the open boundaries as well as at discrete points within the sea, were measured concentrating on a period of 40 days in the stormy season from March to April. Some 200 current meters (most also recorded temperature) were deployed, of which 30 were lost, together with 5 offshore tide gauges. More than 10 ships collected hydrographic data from over 83 stations . The Netherlands organised a collection of meteorological data. The northern boundary of INOUT was from Wick to 59° 20' N, 0° E then along this latitude to the Norwegian coast. The southern boundary crossed the English Channel from Portland to Cherbourg, approximately along the meridian 2° W.

One of the most important reasons for the cooperative exercise was the need to provide large data sets for the evaluation and running of physical and ecosystem numerical models.

Data underwent intradisciplinary processing and interdisciplinary evaluation.

Intercomparison of Instruments

There was no field comparison station for moored instrumentation.

Laboratory techniques in use for calibrating current meter compasses were compared and shortcomings eliminated prior to the exercise. The two main types (Plessey and Aanderaa) of current meter used in the exercise were compared in a simplistic way on four of the rigs and showed that at certain times the two types could give differing responses to the same velocity field simply because of differences in instrument and rig design. This point should be borne in mind whenever comparing data across instruments.

Previous JONSDAP Exercises

The first JONSDAP achieved the systematic collection of data from a network of moored stations and coastal observation sites in the North Sea in the period 1971 to 1973.

The second experiment (JONSDAP 73) was a programme of tide and current measurement in the Southern Bight of the North Sea from September to October 1973.

Data Activity or Cruise Information

Data Activity

No Document Information Held for the Series

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: