ST-VAL Breakout Summary Gary Corlett

ST-VAL Breakout 16:20 Introduction and objectives for session (G Corlett) 16:30 The Data Buoy Co-operation Panel (DBCP) and its role within GHRSST (D Meldrum) 16:45 Discussion on current data buoy usage within GHRSST (all) 17:10 GDS2.0 SSES overview (G Corlett) 17:25 GDS2.0 SSES discussion and feedback (all)

Objectives Obtain feedback on data buoy usage within GHRSST for DBCP – Define priority regions of interest Progress towards implementation of GDS 2.0 SSES – What are the issues/problems

Regions for DBCP Which area would GHRSST recommend for a pilot project high resolution drifter deployment? High latitudes, the tropical Atlantic or the western Pacific as the current areas of high priority. – Highest priority would be southern high latitudes.

Data buoy usage in GHRSST (1) Summaries were made by – ATSR/ESA – NOAA-NESDIS – NAVOCEANO – CMS/OSI-SAF – Bureau of Meteorology. This was followed by a summary on using ARC data to QC historical buoy data (Met Office Hadley Centre).

Data buoy usage in GHRSST (2) Nearly all groups obtain their data via the GTS Markedly different QC approaches and probably QC results. MODIS uses NAVOCEANO buoy data with extra QC

Data buoy usage in GHRSST (3) Bill Emery paper on biases between different drifting buoy manufacturers. – Hard to quantify on regional biases as there is a regional distribution in buoys from different manufacturers. Difficulties in separating the performance of the buoy from the performance of algorithm – Facilitated by multi-way match-ups – All MDBs should be incorporated into MyOcean MDB for exactly this reason.

Other Issues QC should be applied to moored buoys and well as drifting buoys (if not already) Is current drifter network sufficient for our needs? Buoy IDs not always unique – Change to seven character IDs How to obtain non-GTS buoy data?

Actions Pierre Le Borgne – To add Bob Evans, Nick Rayner, Dick Reynolds and Gary Wick to the MF buoy blacklist mailing list Bob Evans – To provide details of extra QC steps done to buoy data prior to ingestion into MODIS MDB.

Tasks The exchange of buoy black lists between groups An investigation into the impact of varying QC approaches Separate NRT activities/requirements from offline/CDR requirements. Include moored buoys to QC procedures Assess current buoy coverage and identify areas where additional data are needed for SSES. Consult widely with buoy providers to identify non- GTS historical buoy data, starting with latest ICOADS release.

Suggestions (Recommendations) DBCP/JCOMM should carry out a controlled buoy inter-comparison L2P producers should use multi-sensor matches as a minimum for rejecting bad buoys DBCP/JCOMM should ensure all buoys have unique IDs. DBCP/JCOMM should target Southern high latitudes for a pilot project deployment for high resolution drifters.

GDS 2.0 SSES (1) SSES must – Comprise bias and standard deviation relative to agreed reference source Quality indicator by QA4EO guidelines – Supported by a quality level – Be defined according to the SSES Common Principles Maintained on GHRSST website – Be documented and traceable Maintained on GHRSST website

GDS 2.0 SSES (2) SSTs should be the best estimate prior to SSES production – Responsibility of the SST producer SSES are for users NOT for producers Common scale for quality level – Scale of 2 (worst quality) to 5 (best quality) – Clearly defined for each producer – Derivation of quality indicator to be traceable, i.e. documented and available to users.

SSES Common Principles (1) Content: – A bias (not a correction term) and a standard deviation reflecting the local accuracy (at pixel) of the SST estimate – Application of SSES is consistent with the product definition (skin; sub-skin) At present the reference is drifting buoys – By convention (only really global source)

SSES Common Principles (2) Hierarchical references can be used – Global stats to DRIFTING BUOYS – Regional stats using other reference sources Radiometers GTMBA L4 analyses Use of common match-up thresholds – Centre pixel clear; +/- 2 hrs (ideally 30 mins)

SSES Common Principles (3) Continuous fields preferred – No discontinuities between Quality Levels – Discontinuities may be inevitable SSES must be free from diurnal variability – Ideally estimated from night time match-ups L2P producers that provide SST-skin should use, as a minimum, a constant offset of 0.17 K to adjust SST- skin to SST-sub-skin for SSES production. – If sufficiently accurate wind-speed data is available then L2P producers are encouraged to allow for the wind speed dependence of the skin to sub-skin adjustment.

SSES Review Summaries were made for ATSR, IASI, NAVOCEANO, CMS/OSI-SAF, MODIS and the Bureau of Meteorology. Good progress was being made towards providing uniform SSES across all products – Some incompatibilities with the SSES common principles remain across most products. Diurnal variability; match-up limits – Further iterations and refinements will be sought over the next year.

Documentation Still an issue – Some schemes have no documentation at all Need to provide guidance for users – For website and user manual SSES schemes should ideally be peer-reviewed

Other Issues Large regions have little if any drifters – How can users we assured that SSES are valid in these regions? Future sensors will be able to use Level 1B uncertainties and have much better defined retrieval errors. – How should these be incorporated into SSES and L2P?

Tasks Continued refinement and adoption of the SSES common principles Provision of documentation for the website and user manual Peer-review of SSES schemes

Next meeting The session was concluded with a discussion regarding a inter-GHRSST ST-VAL meeting. The group recognised the overlap in personnel with both the DVWG and HL-TAG and so a combined meeting of all three groups will be sought in February – Location TBD