STVAL Report Gary Corlett

Introduction At the 9 th GHRSST Science Team meeting, a proposal was put forward to join together the SSES-WG and the VAL-TAG to form the Satellite SST Validation Working Group (STVAL WG). – This proposal was accepted by the Science Team. The new group’s objectives are to 1.Establish and promote guidelines for satellite SST validation Coordinate discussions on validation techniques Draft a set of common guidelines 1.Objectively examine GHRSST-PP L2P data and to provide meaningful SSES for users Coordinate and homogenize the quality information in L2P between producersThe

Activities within STVAL The STVAL group’s activities are split into three areas: 1.Validation using in situ thermometry, including QC of in situ data Guidelines for producing match-ups (generation of MDB) Production of SSES Agree common guidelines for SSES 2.Validation using in situ radiometry, including Calibration traceability to standards Guidelines for producing match-ups Inter-comparisons 3.Validation using reference satellite sensor, including QC of reference sensor Methodologies Progress in the last year has mainly focussed on the areas 1 and 2

Progress (1) QC of in situ buoy data Sub-group of STVAL to look at QC of in situ buoy data; led by Pierre Le Borgne Common reporting system established with JCOMM through JCOMMOPS GHRSST MDB monitoring tool developed by Steinar Eastwood

MDB Monitoring METOP MDB monitoring tool: Request access to other MDBs

Progress (2) GHRSST has written to DBCP with new recommendations DBCP set up a small ad hoc working group to address the issue and make recommendations. – The group recommended to organise in due course a face-to-face meeting with a few GHRSST key player. The Panel requested the DBCP Technical Coordinator to coordinate with appropriate experts and to develop a new document summarising requirements for the reporting of high temporal resolution SST data from buoys.

Recommendations to DBCP That comprehensive hourly reporting from drifting buoys as standard will be of immediate benefit to fundamental knowledge of diurnal variability globally noting that such reporting is very likely to be heavily utilized within GHRSST diurnal variability and validation activities immediately and in the future by operational DVAC. Reporting in metadata of the nominal or design depth in calm water of the drifting buoy SST to an absolute accuracy of ±5 cm is encouraged to facilitate diurnal variability analysis. Reporting of geographical location with an absolute accuracy of ±0.5 km or better is important for high resolution SST analysis and satellite SST validation. (We note that calculation of hourly velocity vectors arose in the discussions, and would require ±0.01 km resolution.) Absolute accuracy of drifting buoy SST of ±0.05 K is recommended based on the needs of satellite SST validation, with SSTs reported with a resolution of 0.01 K (to fully resolve diurnal cycles in SST). That the NetCDF CF-1.3 standard name table is adopted for use by reporting agencies. Reporting of the time of SST measurement to an absolute accuracy of ±5 minutes. Reporting at hourly intervals (for purposes of matching to satellite observation and resolving diurnal cycles in time), but there is no requirement that the reports be made on or close to integer UTC hours.

Progress (3) A request was made to STVAL at the 9 th Science Team meeting to investigate the performance of possible reference sources for the derivation of SSES. The current reference data set used in GHRSST is that provided by surface drifting buoys. – Other potential reference data include ship-based radiometers, moored buoys, and conventional ship measurements from engine room intakes or hull-mounted sensors. To give an indication of the performance of each dataset, the following table summarises statistics of match-up differences uncertainties for the various reference sources, in comparison to 1-km SSTs from AATSR. – The variance of the comparison has been reduced by limiting the spatial and temporal limits to < 1 km and  2 hours.

Reference sources Comparison of various reference sources to AATSR

Progress (4) Support to CEOS Working Group on Calibration and Validation (WGCV) Infrared and Visible Optical Sensors (IVOS) – Presentation on the work GHRSST is doing to get the community to agree on guidelines and method of satellite SST validation. – The agreement and support of a community is seen by IVOS as a key step in establishing the Quality Assurance Framework for Earth Observation (QA4EO) proposed by CEOS. The robust derivation and provision of “Quality Indicators” underpins the new Quality Assurance Framework for Earth Observation (QA4EO) that has recently been developed for GEO (Group on Earth Observations) through a consultation process led by the CEOS-WGCV. The QA4EO process is based on the adoption of community defined best practises with GHRSST often used as a founding example of good practise and on how it should be implemented within other applications. See talk on Thursday.

Two parts: Laboratory (NPL) April 2009 Laboratory and ocean viewing (Miami) May 2009 (Participants self-funded) CEOS IR radiometer inter-comparison Third in a series of inter-comparisons establish degree of equivalence (biases) between participant’s – Reference black bodies – IR radiometers under lab conditions – IR radiometers as used viewing Ocean (SST) Ensure robust traceability to SI (via NIST and NPL) Establish protocols based on QA4EO to facilitate future comparisons and strategy for maintenance of long-term traceability Pre-cursor for Land Surface Temperature community

GHRSST use of SOT Data The limited use of ship measurements by GHRSST is mainly due to a combination of their: – Non-uniform global data coverage, and – Relatively high uncertainty, in the case of non-radiometric measurements. The GHRSST project would like to establish closer links to the Ship Observations Team (SOT) to address both these issues, as improved coverage and uncertainties of SST data from ships would benefit a number of areas within GHRSST, not least in: – Satellite SST validation – Reanalysis – Diurnal warming studies

Recommendations To maximise the impact and benefit of existing and future SST measurements from ships, GHRSST recommends that the SOT considers: – Adding the provision of radiometric skin SST data to its portfolio of measurements. – Using GHRSST data to characterise the uncertainties of non-radiometric SST measurements from existing ship data. – Establishing a working group to collaborate with GHRSST to better define requirements for measurements of SST from ships.

SSES Review Reasonable agreement on reference source Poor agreement on reference QC Poor agreement on match-up limits Poor agreement on SSES principles Add or subtract biases? Skin, sub-skin, (buoy-depth) or foundation? – Advice needed from DV-WG Day time and/or night time? Are discontinuities okay? – Global or regional SSES

STVAL Membership The current members of the STVAL group are: – Sandra Castro, Jean-Francois Cayula, Gary Corlett, Steinar Eastwood, Bob Evans, Chelle Gentemann, Andy Harris, Jacob Hoeyer, Alexy Kaplan, Pierre Le Borgne, Leon Majewski, Bruce McKenzie, Peter Minnett, Jon Mittaz, Chris Mutlow, Anne O’Carroll, Jean-Francois Piollé, Igor Tomazic and Werenfrid Wimmer. Members of the in situ QC sub-group are: – Emmanuelle Autret, Steinar Eastwood, Jacob Hoeyer, Pierre Le Borgne, Leon Majewski, Matt Martin, Bruce McKenzie and Sonia Pere.

For more information STVAL breakout on Tuesday afternoon – Russian River Valley Ballroom from 14:00 – Overview later today To join and participate in STVAL see Gary Corlett