Metadata Report for BODC Series Reference Number 642814

• 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

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.

Specifications

These specification apply to the MK3C version.

Further details can be found in the specification sheet.

James Clark Ross JR06 CTD Data Document

Sampling strategy

A Conductivity-Temperature-Depth (CTD) probe was used to vertically profile the temperature and salinity of the water column. A total of 108 CTD casts were performed during the cruise.

Instrumentation and data processing by originator

• CTD unit and auxiliary sensors

  The CTD system used on the JR06 was the MKIII CTD and the RVS CTD level A.

• Sampling device

  Salinity samples were taken from all bottles at the beginning and end of the CTD transects. These samples were processed on the Guildline Autosal.

• Data Acquisition and Initial Processing

  CTD Data

  The majority of the CTD data for Leg 1 and all the data from Leg 2 have been transferred onto the RVS Level 'C' system. The data on the Level 'C' have been calibrated using the 1993 instrument calibrations and the pressure has been corrected for the 3 to 4m offset noted on the deck unit when the CTD was at the water surface. These data have not yet been finally corrected using in situ corrections. In situ temperature has been determined on the CTD casts using digital reversing thermometers. The Level 'C' system was calibrated using the calibration file provided by IOS for the WOCE cruise preceding cruise JR06.

• Problems

  While the MKIII CTD performed faultlessly the RVS CTD level A did not. It had a tendency to suddenly stop transmitting data to the Level B which required CTD casts to be restarted on more than one occasion. The new rosette system worked well although there were a few problems the more serious one being the loss of one of the bottle caps which have a tendency to unscrew themselves.

BODC post-processing and screening

• Reformatting

  The data were converted from Ascii format into BODC internal format (QXF) to allow use of in-house visualisation tools.

• Screening

  Reformatted CTD data were transferred onto a graphics work station for visualisation using the in-house editor SERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated quality control flag to 'M' for suspect values and 'N' for nulls.

• Banking

  Once BODC quality control screening was complete, the CTD QXF files were archived in the BODC National Oceanographic Database and the associated metadata were loaded into an ORACLE Relational Database Management System.

Quality control report

• Salinity

  The data are erratic with "loops" throughout the downcasts. These have not been flagged but caution should be taken when using the data. Spikes in salinity have been flagged. Data quality reports have been made where casts have started well below the surface as well as where the presence of "looping" is quite extreme and may affect the overall quality of the data.

• Temperature

  The data are erratic with "loops" throughout the downcasts. These have not been flagged but caution should be taken when using the data. Spikes in temperature have been flagged. Data quality reports have been made where casts have started well below the surface as well as where the presence of "looping" is quite extreme and may affect the overall quality of the data.

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

No Project Information held for the Series

Data Activity or Cruise Information

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: