Page 1Validation Workshop, 9-13th December 2002, ESRIN

ENVISAT Validation WorkshopAATSR Report

Marianne Edwards

Space Research Centre

Department of Physics and Astronomy

University of Leicester

Page 2Validation Workshop, 9-13th December 2002, ESRIN

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

Page 3Validation Workshop, 9-13th December 2002, ESRIN

Page 4Validation Workshop, 9-13th December 2002, ESRIN

AATSR Validation Workshop - outcome

Initial results show that AATSR data are of excellent quality and meet the SST accuracy requirements

1860 Matchups

Page 5Validation Workshop, 9-13th December 2002, ESRIN

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

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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

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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

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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

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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

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Conclusions

Limited results are extremely promising, showing no serious anomalies in the SST products and performance close to specifications

Only a partial validation 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

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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.

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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.

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Recommendation

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