Metadata Report for BODC Series Reference Number 604923

• 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

A visual inspection of each individual thermistor bead series indicates generally good data from the thermistor bead at depth 5.0m. Data from the thermistor bead at depth 13.3m are extremely 'noisy' throughout the deployment, and the data from all other thermistor bead depths are extremely 'noisy' from 7 October until the end of the deployment. These data have subsequently been flagged as suspect.

A comparison between these data and the CTD temperature sensor data collected at the same time was also conducted. The CTD cast number with which the comparison was made is also given, this will be the CTD taken close to the time of deployment and/or recovery of the thermistor chain.

The difference between the two temperatures is listed below:

where D1 (°C) = CTD temperature - thermistor bead 1 temperature, D2 (°C) = CTD temperature - thermistor bead 2 temperature etc. Thermistor bead 1 is the top bead (i.e. the one attached to the logger) and thermistor bead 12 is the bottom bead.

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 Thermistor Chain

Instrumentation

The thermistor string comprises 11 sensors electrically connected to a logger. The sensors are equally spaced along the string; string lengths range from 10m to 400m. Sensors used are Fenwal 2K iso-curve thermistors (type GB32JM19) with time constant of approximately 3.5min for 63pcent of step change. The thermistors have identical calibration curves to within ±0.1 °C.

Standard temperature ranges are: low range (-2.46 to 21.48 °C), high range (10.08 to 36.00 °C), wide range (-0.34 to 32.17 °C). A resistor, accurate to ±0.025deg C, within the logger is used to select the range.

Calibrations

The calibration formula, corresponding to the temperature range chosen, converts the logger reading N to degrees C with an accuracy of ±0.05deg C, The worst accumulated error (taking into account the accuracy of the formula, the thermistor and the resistor) is ±0.175 °C. These errors can be reduced by carrying out temperature calibrations at 0 °C. This can give an accuracy of ±0.05 °C. The theoretical limit of accuracy is ±0.0125 °C, approx. To approach this accuracy better interpolation formulae and frequent calibrations are required.

The data are logged either by Aanderaa TR loggers or by SeaData loggers (which incorporate a temperature sensor and hence record 12 channels).

General Data Screening carried out by BODC

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:
  • Times for instrument deployment and for start/end of data series
  • Length of record and the number of data cycles/cycle interval
  • Parameters expected 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 or depth 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 data values will not be altered.

The following types of irregularity, each relying on visual detection in the 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 then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

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

• Maximum and minimum values of parameters (spikes excluded).
• The occurrence of meteorological events.

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

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

• Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
• Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
• Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

Data Activity or Cruise Information

Data Activity

North Sea Project POLRIG#C35BT

The thermistor chain mooring was deployed as part of the North Sea Project Survey at Site B.

A thermistor chain, incorporating eleven thermistor beads, was moored as a single point mooring beneath a toroidal buoy. The data logger was positioned just above the chain and also incorporated a thermistor bead. The beads were positioned at the following depths below the surface of the water (the top bead is the one incorporated in the logger):

5.0m, 5.3m, 9.3m, 13.3m, 17.3m, 21.3m, 25.3m, 29.3m, 33.3m, 37.3m, 41.3m, 45.3m

The accuracy of the thermistor beads was ±0.05°C.

Fixed Station Information

Fixed Station Information

North Sea Project Survey Mooring Site B and CTD Site CK

Site B was one of six fixed stations where moorings were deployed during the North Sea Project survey. This location is also one of 123 North Sea Project CTD Sites.

The site was characterised by weak tidal currents, up to a maximum of 0.5 m/s, and the water column was stratified in the summer months.

The rigs deployed here lie within a box bounded by co-ordinates 55° 29.85' N, 005° 27.96' E at the southwest corner and 55° 31.40' N, 005° 31.28' E at the northeast corner. Magnetic variation at this site was 2.8°W.

The deployment history for Site B is summarised below:

Where

• CM = Current Meter (Aanderaa or S4)
• THCH = Thermistor Chain

Related Fixed Station activities are detailed in Appendix 1

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: NSP Survey B and CTD Site CK

Related series for this Fixed Station 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.