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The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future

The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future. David Llewellyn-Jones C J Merchant*, O Embury*, G K Corlett Space Research Centre Department of Physics & Astronomy University of Leicester, UK *University of Edinburgh.

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The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future

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  1. The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future David Llewellyn-Jones C J Merchant*, O Embury*, G K Corlett Space Research Centre Department of Physics & Astronomy University of Leicester, UK *University of Edinburgh

  2. AATSR, Climate Record and Validation • AATSR and its Data • ATSR Re-processing for Climate (ARC Project) • Recent Validation Results • Validation Priorities for the Future

  3. ATSR Viewing Geometry ATSR Viewing Geometry

  4. ATSR Scan sequence –showing on-board Calibration System Blackbodies viewed every scan.

  5. An ATSR on-board Black BodyPeering into the Void - How Black is Black?

  6. ATSR Main Characteristics • 7 spectral channels (like AVHRR, or MODIS • 3 thermal IR: at 3.7 μm, 11 μm, 12 μm • 4 Vis/NIR: at 0.55 μm, 0.67 μm, 0.87 μm, 1.6 μm) - provides basic SST information • Dual view • Nadir and 55° to nadir • Gives a direct measurement of atmospheric effects • Very effective for dealing with aerosol contamination • On board calibration • 2 on-board black bodies for IR calibration • VISCAL unit for visible channel calibration

  7. ATSR Characteristics - 2 • AATSR (ATSR-3) Currently flying on ESA’s Envisat • Swath-width - 500 km • Dual view less effective at wider swath-widths • Field-of-view - 1 km at nadir • Same as AVHRR • Stirling Cycle Coolers, cooling low noise detectors to 80K • Gives optimum detector performance and exceptional image clarity

  8. ATSR Data Standard Products:- • SST data produced at 1km resolution, • also gridded at 0.5˚ and 10 arc-min long-lat • ToA BTs also available (L1b) • Full range of Level 1b, Level 2 Products and Browse products available from ESA • Revised Data Policy • To gain access, please contact: eohelp@esa.int

  9. ARC Project ATSR Re-processing for Climate (ARC) • Consortium with Relevant experience/Skills • U Edinburgh – (Retrievals) • U Leicester – (Validation, incl overlap analysis • Southampton Oceanography Centre – Assessment with in situ data • (K Met Office/Hadley Centre – assessment for climate purposes • Objective: to generate Climate-standard (GCOS-compliant) SST data-set from standard ATSR level L1b data • Analogous to AVHRR Pathfinder teams

  10. Skin to Depth Adjustment • skin effect and stratification: 20 cm, 1 m • for AATSR also 30 min orbit time adjustment • Uncertainty model ARC Procedures • Made record homogeneous at BT level (Overlap periods, drift effects etc) • ARC Algorithms: • Cloud Detection • ‘Obvious’ Clouds: some image pre-processing • ‘Marginal’ Clouds: Bayesian probability-of-clear calculation • SST Retrieval • coefficients • includes adjustments to coefficients to compensate for inter-satellite calibration discrepancies

  11. Dependencies on TCWV, wind etc also within +/- 0.1 K target ARC SSTs - Assessments of accuracy

  12. Accuracy (Lack of Bias) Assessment: AATSR

  13. Accuracy (Lack of Bias) Assessment: ATSR-1

  14. Assessments of precision

  15. Precision estimates (0.1 deg data) • AATSR “drifter depth” SSTs from ARC have lower uncertainty than drifting buoy SSTs • Independent 3-way analysis by Katie Lean, UKMO

  16. ARC - Tropical Moored Buoys Assessment of stability

  17. Stability: 0.03 K/dec for 1993-2009* *in the tropics – which is the only place we can make an assessment

  18. ARC D2 – in situ (drifter + GTMBA)

  19. HadSST3 vs ARC SST0.2m, 1991-2006: global mean anomaly, co-located atsr1 det. temp. drift Pinatubo geoloc dodgy atsr2 Comparison by Nick Rayner

  20. Read all About it! • Journal: • Special Issue on AATSR • Special Issue on AATSR • Now Online; Due for Publication 2012 • 19 Articles • Covers whole range of Applications • Acknowledgments due to: • John Remedios and Roger Saunders • (Co-editors) • Editorial staff of JRSE • Not forgetting PJ Minnett, Deputy Editor!

  21. Reference for much of this Material:- Please cite this article as: Embury, O., et al., Remote Sensing of Environment (2011), doi:10.1016/j.rse.2011.02.028 O. Embury et al. / Remote Sensing of Environment xxx (2011) xxx–xxx Paper version available in 2012 Now available online to JRSE subscribers

  22. The Future for ARC • Programme of updates planned • ARC Methods to be used to generate Standard Products for ESA • ARC Data are the Foundation for SST Element in ESA’s Climate Change Initiative (CCI)

  23. Get ARC Data! wwww.neodc.rl.ac.uk • From NEODC (Part of BADC) • URL is • If you browse datasets, ARC is at the top of the list (under AATSR). • Need to get a BADC registration and password • If all else fails, contact Chris Merchant • Netcdf files • Readme and Briefing Doc • Will collect user e-mails

  24. Validation Issues • Objectives of a Validation programme include: • Provide Basic Quality Control Information • Provide in situ Reference Measurements which are calibrated to recognised standards • Establish achievable limits of accuracy and Precision

  25. What is needed? • ‘Generic validation’ • Concentrate on variable, not the mission • Essential during Data-gaps • Use Traceable Calibration for Reference Data • For SST at this time, this means Radiometers

  26. Science Museum London Science Museum London Wow! New Gallery: “Atmosphere - Exploring Climate Science”

  27. EENVISAT Europe’s largest satellite AATSR , launched March 2002 Sun-synchronous orbit, 1030 local time daylight descending

  28. Against US coastal moorings -0.04 K step same time as ECMWF upgrade from 60 to 91 model levels

  29. ARC SSTs • Final period of ARC involved assessment of ARC SSTs at UoE, UoL, NOCS and Met Office • At final team meeting in June, prime focus was a synthesis of these results • Outcome was the briefing document, which aims to summarize our main conclusions about the characteristics of the ARC SSTs

  30. L3C netcdf files • sst_skin • radiometric skin temperature at time of observation • sst_depth • SST adjusted for skin and diurnal effects for nominal depths of 0.2, 1.0 m • Adjusted to consistent satellite overpass time (10:30 LECT) • uncertainty • Estimated retrieval uncertainty based on theoretical algorithm performance, sensitivity to radiometric noise, number of clear-sky pixels • time • number_of_pixels

  31. Planned upgrade: v1.1 • Expected before end 2011

  32. Planned upgrade: v1.2 • Expected before end 2012, and will:

  33. Summary of ARC improvements - 1

  34. Summary of ARC improvements - 2

  35. ENVISAT, People and the AATSR

  36. Made record homogeneous at BT level ATSR-2-ATSR-1 overlap Reconcile 11 & 12 BTs AATSR-ATSR2 overlap Adjusted BT calibration for 3.7 & 11 (accounting for spectral responses)

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