Metadata Report for BODC Series Reference Number 1095375

• 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

SIMORC Total Angola MANGO CTD Data Narrative

Narrative

Four different CTD instruments (Ocean Seven 316 multi-parameter probe, Idronaut, Horiba U-22 multi-parameter probe or SBE19+) were deployed offshore Angola as part of Environmental Baseline Surveys.

Data Quality Information

The following data quality checks were applied to temperature, salinity, turbidity, redox potential, oxygen concentration and oxygen saturation, pH and suspended sediment measurements:

• Changes too sudden to be physically feasible (spikes) were flagged suspect.
• Changes too large to be physically feasible (such as increases to oxygen saturations in excess of 150%) were flagged suspect.

A regular occurrence of inconsistent data was the first datacycle of many profiles; showing a particularly low temperature and a salinity of near zero. This was assumed to represent cases where the instrument was partially out of the water and was flagged suspect.

Series reference 1095326 oxygen saturation data should be discarded as meaningless as there was no actual oxygen concentration data measured to support the calculation of percentage saturation.

pH data from series reference 1095271 shows a significantly differently shaped profile and should be treated with caution.

Concentration of suspended sediment was null (not measured) for all series and was therefore deleted.

Redox potential profiles from series reference 1095105 and 1095098 were very similar, as were profiles from series references 1095074 and 1095086. The two sets of profiles were situated far apart from each other on the redox scale. 1095105 and 1095098 were shifted to the left with lower redox potential values than the other set.

Data Access Policy

SIMORC data access conditions

The data collated and held at BODC on behalf of the SIMORC project are restricted. However, the data will be available to download from the Official SIMORC Website, as part of the project protocol. The data set will initially include data from the oil companies TOTAL, Shell and BP.

Narrative Documents

Idronaut Ocean Seven 304 CTD

The Ocean Seven 304 CTD is a high performance CTD probe with very small diameter and extremely low power consumption. It can be easily integrated/adapted to third-party systems like floating profilers and/or buoy-moored systems. It does not require pumps or any other external device to flush the sensors, which minimizes its power consumption. The 304 CTD offers a combination of 16-bit high resolution data accuracy, with long-term sensor stability. The user can select the proper conductivity range i.e. for salt or fresh water.

Sampling modes

User selectable sampling/operating modes include: continuous, pressure, timed, conditioned and burst.

Real time communications

The Ocean Seven 304 CTD communicates with a computer via a standard RS232C interface. Real-time data can be acquired by means of the REDAS Windows software. An optional RS422 interface overcomes the limitation of the RS232C cable maximum length (200 m) and allows the probe to transmit data through distances up to 1000 m. The communication speed is user selectable among: 9600, 19200, 38400 and 57600 bps. A Bluetooth wireless interface can be optionally added to the wired interfaces.

Software

Idronaut programmes operating under Windows 98se/ME/2000/XP allow the operator to configure the Ocean Seven 304 CTD data acquisition and logger functions and upload data from the 128-MByte internal memory. They are:
ITERM: terminal emulation programme to easily communicate with the Ocean Seven 304 CTD using the probe integrated operator interface.
REDAS: data processing and retrieval programme which allows the display and plotting of conductivity, temperature, pressure and derived variables such as salinity, sound speed, density, according to UNESCO formulas and recommendations.

Data storage and battery endurance

The Ocean Seven 304 CTD allows the storing of 4,100,000 data sets each one being composed of the reading of CTD sensors plus the acquisition date and time. The batteries are sufficient to keep the CTD continuously on for 36 hours in continuous sampling mode and at the maximum sampling rate. Further battery endurance can be obtained by using lithium batteries. Whenever the CTD operates in "Timed, Burst and Conditioned" modes, the battery endurance is considerably extended because the CTD waits for the interval between acquisitions in "Sleep mode".

CTD chains

Chains of Ocean Seven 304 CTDs are deployed by easily clamping the CTDs with a screwdriver to a rope. Chains of OS304 CTDs can be used to profile or perform long-term monitoring by properly configuring the CTD data acquisition method. Furthermore, the Bluetooth wireless connectivity option allows the instant recovery of data stored in the CTDs internal memory once they are back to the surface. OS304 CTD Bluetooth unique addressing identification code allows the operator to select one OS304 among the others present in the chain.

Specifications

Further information on the instrument can be found on the Idronaut website.

BODC Processing

Data were received by BODC in Comma Separated Variable files. They were reformatted to QXF format using BODC transfer function 422. The following table shows how the variables within the files were mapped to the appropriate BODC parameter codes:

Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO.

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

System of Industry Metocean data for the Offshore and Research Communities (SIMORC)

The EU-funded SIMORC project is a collaborative effort between MARIS (Netherlands), BODC (UK), the International Association of Oil and Gas Producers (OGP) and IOC-IODE to provide a harmonised and quality controlled metocean data set from data collected by oil and gas producers, accessible through the SIMORC protocol.

Data Activity or Cruise Information

No Data Activity or Cruise Information held for the Series

Fixed Station Information

Fixed Station Information

SIMORC: TOTAL Angola Clover Fixed Station Document

This site is located in the Clover field, Block 17, offshore Angola.

The nominal position of the site is 7.3453° S; 11.7225° E with an assumed water depth (taken from GEBCO) of 1289 metres.

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: Angola, B17, Rosa Lirio

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.