Metadata Report for BODC Series Reference Number 34242
No Problem Report Found in the Database
Open Data supplied by Natural Environment Research Council (NERC)
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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 K (Celtic Sea) Data Processing Notes
Clock lost 4 seconds over 64 days, 6.5 hours; the cycle interval and time values have been corrected.
Instrument Characteristics and Calibration Factors
Aanderaa Current meter/Pressure recorder, logger 1506, DIG 4143
|Original sampling interval||15 minutes|
|Pressure sensitivity at 10.08°C||0.13380Hz/mb|
To convert pressure to elevation the following values should be used:
|Density (from CTD casts)||1026.94kg/m3|
|Gravitational acceleration constant||9.811m/s2|
IOS Celtic Sea Experiment 1980
An experiment was conducted by I.O.S. Bidston in the Celtic Sea during the period August to October 1980, in order to study sea level, vertical current structure and circulation patterns under stratified conditions.
The experiment complemented one in March to May 1978 which studied the Celtic Sea under homogeneous conditions. 19 rigs containing recording current meters, thermistor chains or pressure recorders were deployed for 50 days at 8 stations. The density field was measured during both the deployment and the recovery legs by continuous monitoring of sea surface temperature and conductivity and by recording CTD profiles.
No Data Activity or Cruise Information held for the Series
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||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.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|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|
|O||Improbable value - user quality control|
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|