Quality Control Standards for SeaDataNet

1. Quality Control Standards for SeaDataNet • Review status at 1st Annual Meeting (March 2007) • Review developments over last year • Current status • Future work

2. Quality Control Standards for SeaDataNet • OUTLINE OF QUALITY CONTROL DOCUMENT • Introduction • Why is quality control is needed? • Information to accompany data • Automatic checks • “Scientific” quality control • CTD (temperature and salinity) • Current meter data (including ADCP) • Wave data • Sea level • Biological data, etc., • Quality flags • Documentation

3. Quality Control Standards for SeaDataNet Data quality control has the following objective: “To ensure the data consistency within a single data set and within a collection of data sets and to ensure that the quality and errors of the data are apparent to the user who has sufficient information to assess its suitability for a task.” (IOC/CEC Manuals and Guides 26, 1993) Quality control, if done well, brings about a number of key advantages: • Maintaining standards • Consistency • Reliability

4. Quality Control Standards for SeaDataNet For all types of data information is required about: • Wherethe data were collected: location (preferably as latitude and longitude) and depth/height • Whenthe data were collected (date and time in UTC or clearly specified local time zone) • Howthe data were collected (e.g. sampling methods, instrument types, analytical techniques) • How the data are referenced (e.g. station numbers, cast numbers) • Whocollected the data, including name and institution of the data originator(s) and the principal investigator • Whathas been done to the data (e.g. details of processing and calibrations applied, algorithms used to compute derived parameters) • Comments for other users of the data (e.g. problems encountered and comments on data quality)

5. Quality Control Standards for SeaDataNet IODE/JCOMM Forum on Oceanographic Data Management and Exchange Standards • Date and time: recommended to adopt the ISO-8601 standard (using extended format) where appropriate while recognising some limitations • Latitude, longitude, altitude: recommended to adopt the ISO-6709 standard • Countries: recommended to adopt the ISO-3166 (3166-1 and 3166-3) standard Reference: Intergovernmental Oceanographic Commission 2008 IODE/JCOMM Forum on Oceanographic Data Management and Exchange Standards, IOC Project Office for IODE, Oostende, Blegium 21-25 January 2008. Oostende, Belgium: IOC/IODE Project Office, 45pp. (IOC Workshop Report No. 206) (English)

6. Quality Control Standards for SeaDataNet Basic automatic checks for all data types: • Date and time } • Latitude and longitude } ? QC flags ? • Position must not be on land } Other automatic checks: • Impossible speed • Spike • Gradient • Density inversion • Pressure increasing • Global range • Regional range • Deepest pressure • Check for duplicates

7. Quality Control Standards for SeaDataNet Visual inspection of data • Pressure/depth series (e.g. CTD) • Property-property plot • Time series (e.g. current meter, sea level) • Scatter plot (e.g. current meter) • Map covering the locations of series • Ensure that data are free from instrument-generated spikes, gaps, spurious data at the start and end of the record and other irregularities • Apply quality flags • Quality flags do not change the data • Visual inspection can be subjective, dependent on experience

8. Quality Control Standards for SeaDataNet Outcomes of Standards Forum relevant to QC No recommended standards identified, but: • Temperature and salinity profiles: GTSPP to revise IOC Manuals and Guides No. 22 • Surface T&S: GOSUD to revise their QC document • Sea level: revise ESEAS QC document in close collaboration with the GE-GLOSS • Currents: consolidate input from US IOOS with IOC Manuals and Guides No. 26; add info on HF radar • Surface waves: update IOC Manuals and Guides No. 26; US IOOS will provide the US national waves plan • SeaDataNet QC flags are a sensible extension to handle situations appropriate for a greater range of variables • Develop “Guidelines for a Manual on Quality Control” document

9. Quality Control Standards for SeaDataNet SeaDataNet quality control flags (L201) Flag Short description 0 No quality control 1 The value appears to be correct 2 The value appears to be probably good 3 The value appears probably bad 4 The value appears erroneous 5 The value has been changed 6 Below detection limit 7 In excess of quoted value 8 Interpolated value 9 Missing value A Incomplete information Based on IGOSS/UOT/GTSPP & Argo quality flags

10. Quality Control Standards for SeaDataNet Data Documentation • Comprehensive documentation to accompany the data • All data sets need to be fully documented to ensure they can be used in the future without ambiguity or uncertainty • Compiled using: • information supplied by the data originator (e.g. data reports, comments on data quality) • any further information gained during QC • Includes:instrument details, mooring details, data quality, calibration and processing carried out by the data originator and data centre processing and quality control

11. Quality Control Standards for SeaDataNet Other data types: Discrete Water Sample Data • How trace values (values below the detection limit) identified • What is the precision of the methods (e.g. number of significant figures) • What analyses performed (use parameters descriptions as described in the ICES green book) • What units are used • Duplicate samples taken? • Comments describing each station • Supply calibration document • Station number, site details, sample identifier (or bottle number), type of station, continuous flow etc., • Check profiles vs. regional climatology • Check calibration information available • Compare parameters for predictable relationships (e.g. parameter ratios)

12. Quality Control Standards for SeaDataNet Other data types: Example – nutrients (Baltic) • Plot nutrients against salinity • Compare how nutrients behave – look for outliers in homogeneous water mass • Check sum NO2 + NO3 +NH4 (or phosphate) less than or equal to total nitrogen (or phosphorus) • Check for stable relationship between phosphorus and nitrogen • If NO2 > NO3 check carefully to see if OK • During productive season nutrients should decrease • If hydrogen sulphide present then NO2 and NO3should go to zero and NH4 increase • Look at (plot) dissolved oxygen and chlorophyll (this checks for productivity) • Regional and seasonal behaviour important

13. Quality Control Standards for SeaDataNet Next steps/future work • Version 1 of the QC manual to be completed and available on the project web site by end April 2008 • Extend range of parameters to include, for example: • Surface underway data (e.g. thermosalinograph, shipboard ADCP) • Nutrients, dissolved oxygen (and other chemistry) • Marine geophysics • Extend and improve information on biological data quality control • Follow Standards Forum progress and update QC manual as appropriate • Version 2 of the manual to be available April 2009