ENVISAT Validation Workshop AATSR Report

1. ENVISAT Validation WorkshopAATSR Report Marianne Edwards Space Research Centre Department of Physics and Astronomy University of Leicester

2. AATSR Validation Workshop - overview • General outcome • Clear definition of plans for 2003 and beyond • Identification of critical issues • Recommendations to ESA and to the validation team

4. AATSR Validation Workshop - outcome • Initial results show that AATSR data are of excellent quality and meet the SST accuracy requirements 1860 Matchups

5. The AATSR Validation Plan 2003 and beyond • The AATSR validation team must complete the initial validation phase • The objectives are:- • To determine whether the AATSR instrument is returning an acceptable global skin SST (±0.3 K) • To make an initial assessment of the quality of AATSR SST products in a limited number of sites and seasons, including ATSR-2/AATSR cross validation • To assess the accuracy of the AATSR data retrieved over land • These objectives, as stated in the AATSR Validation Implementation Plan, were agreed by the validation team, ESA and funding partners. These objectives must be met. • In situ data collection has proceeded according to plans. Critical issues are:- • Availability of AATSR data, particularly for the early period • Availability of ATSR-2 data for ATSR-2/AATSR cross validation • Time needed to process and analyse AATSR data • Credibility with funding partners

6. Objectives of ongoing validation • Ongoing validation throughout the whole AATSR mission to:- • Provide assurance of data quality and accuracy for applications such as climate change research • Investigate fully representative range of geophysical conditions • Investigate fully representative range of seasonal cycles • Long term monitoring for instrumental drifts and other artefacts • Validate new products

7. The AATSR Validation Plan 2003 and beyond • In order to meet these objectives, the following activities are planned. • Seasonal validation • Validation over the course of at least one year to assess accuracy of SST retrieval over a range of environmental conditions • Global comparisons to buoys and SST analysis fields by UK Met Office • Global comparisons to other datasets (MODIS, ECMWF, AVHRR etc) • Operation of autonomous radiometers (ISAR, Perth and Townsville ferries, Tahoe, MAERI on Royal Caribbean) • Specific repeat cruises

8. The AATSR Validation Plan 2003 and beyond • Regional validation • Validation in an increasing number of geographic regions • Specific cruises already planned • Australia-Japan-Seattle (March-April 2003) • Gulf of Carpentaria (May/June 2003) • Out of Darwin (June 2003) • Mediterranean (April/May 2003) • Seattle to Sydney (November 2003) • Arctic (Spring 2004) • Additional cruises and deployments of autonomous and precision instruments needed • Opportunities to be sought and identified • Falstaff deployment of the ISAR • Southern Ocean, Arabian Sea, West Africa

9. The AATSR Validation Plan 2003 and beyond • Monitoring of long term trends • Monitoring instrument drift, effects of anomalous environmental conditions • Long term monitoring over desert sites • D. Smith, O. Hagolle • Global comparisons with buoys and other sensors • Validation of new products • Land surface temperature product • Validation plan in place and underway • Other products to be identified

10. Conclusions • Limited results are extremely promising, showing no serious anomalies in the SST products and performance close to specifications • Only a partialvalidation of the instrument has been achieved so far • Data collection activities in initial validation phase are near completion • Significant number of in situ validation points collected • 8 dedicated cruises • 6 instruments running autonomously • Comparisons with other sensors such as ATSR-2 and MERIS are at an early stage

11. Recommendations • Aim to complete initial validation phase mid 2003 • In order to do this, ESA is strongly urged to give high priority to the processing of the May-August AATSR match-up data for the campaigns already carried out, preferably during the early weeks of 2003. • AATSR data already supplied to the validation team must be reprocessed to correct for known processing anomalies including geolocation and other SPRs that are now closed. • A further AATSR validation workshop is recommended for May 2003 at the earliest with the objective of closing the initial validation phase.

12. Recommendations and Actions Data Supply • L1b data distribution: prefer to receive media rather than ftp distribution for fixed sites • L2: ESA should seek higher capacity media for data distribution (eg DVD, DLT) • ESA are urged to supply all blind orbits that are needed for validation • Operational users need to have better information about data supply issues Outstanding scientific issues needing further investigation • Possibility of small biases in SST values • Many more observations needed • Intercomparisons of AATSR and MERIS are at an early stage. Apparent discrepancies with other satellite instruments need further investigation.

13. Recommendation • AATSR data should be released with the understanding that the validation programme and product verification are still incomplete