Metadata Report for BODC Series Reference Number 41275


Metadata Summary

Data Description

Data Category Offshore sea floor pressure series
Instrument Type Tide gauge (unspecified)
Instrument Mounting fixed benthic node
Originating Country United Kingdom
Originator -
Originating Organization Institute of Oceanographic Sciences Bidston Laboratory (now National Oceanography Centre, Liverpool)
Processing Status banked
Project(s) JONSDAP 1976
 

Data Identifiers

Originator's Identifier J57SP2/PDFH4
BODC Series Reference 41275
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1976-03-13 11:22
End Time (yyyy-mm-dd hh:mm) 1976-04-17 13:34
Nominal Cycle Interval 900.0 seconds
 

Spatial Co-ordinates

Latitude 59.33330 N ( 59° 20.0' N )
Longitude 4.51660 E ( 4° 31.0' E )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor Depth 271.0 m
Maximum Sensor Depth 271.0 m
Minimum Sensor Height 0.0 m
Maximum Sensor Height 0.0 m
Sea Floor Depth 271.0 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)
PPSSRL01 1 Decibars RelBotPress Pressure (measured variable) exerted by the water body by fixed in-situ pressure sensor and corrected using co-located air pressure data expressed to unspecified datum by subtraction of a constant
 

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


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

Type 1 Off-Shore Tide Gauge

This instrument was developed at I.O.S. Wormley. It incorporates a seabed mounted pressure transducer interfaced to a 12 channel Normalair-Garret data logger housed in a 56cm diameter aluminium pressure sphere. The frequency modulated (FM) transducer consists of a diaphragm which when flexed by changing hydrostatic pressure varies the gap of a parallel plate timing capacitor in an LC oscillator circuit. The pressure casing enclosing the transducer circuitry is evacuated so that absolute rather than relative pressure is measured. The frequency output is divided down to about 100Hz and is counted over a period of 890 seconds to average out the unwanted fluctuations due to waves: this sampling period gives 50dB (99.999 p. cent) attenuation of energy from 10 second period waves, but only 0.006dB (0.14 p. cent) attenuation of semi diurnal tidal energy.

The integration period of 890 seconds and the subsequent 10 second scanning and recording sequence are controlled by 900 second pulses from a crystal clock. The reading from each channel is recorded serially in either 3 or 4 decade BCD on 0.25 inch magnetic tape and a parity bit is added during each scan by the digital serializer. A synchronizing signal is recorded on a second track of the tape to assist in translating the magnetic tape during the data processing.

The sphere containing the data logger and interfacing electronics is mounted in a tripod frame made of tubular steel with the pressure transducer mounted on the base of the framework and beneath the sphere. The tripod is supported on a disposable heavy ballast frame consisting of welded girders and the two frames are connected by 3 corrodible magnesium alloy links and a pyrotechnic release mechanism. The recorders are deployed as pop up moorings and released by acoustic release.

Data Processing Notes

Clock gained 2 minutes 32 seconds over 35 days 2 hours 12 minutes 28 seconds; cycle interval and time values have been corrected.

Instrument Characteristics

JONSDAP 76 Rig 57

OSTG Mark I Number 15
Sensors SG 1/13 (BODC Series Ref. 41183)
SG 1/16 (BODC Series Ref. 41275)
Nominal sampling interval 900 seconds
Integration period 890 seconds

IOS Data Processing of Off-Shore Pressure Recorder Data

Data processing comprises 2 stages:-

  1. Instrumental drift and depth are removed, thus the drift free series is produced with an artificial mean of zero.

  2. Generally the pressure values have been obtained by integration and averaging over the sampling interval, followed by logging; hence the time value assigned to a data cycle has been chosen as the mid-point between the start and end time of each interval. Some pressure records have been sample rate reduced from the basic time step of the recorder to produce either hourly or 15 minute values, incorporating any timing corrections due to clock error.


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:

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


No Data Activity or Cruise 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:

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