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Earth Observation Science The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future David Llewellyn-Jones.

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Presentation on theme: "Earth Observation Science The ATSR Series, the SST Climate Record and Relevant Validation Programmes for the Future David Llewellyn-Jones."— Presentation transcript:

1 Earth Observation Science 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

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

5 An ATSR on-board Black Body Peering 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:

9 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 ARC Project

10 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 Skin to Depth Adjustment skin effect and stratification: 20 cm, 1 m for AATSR also 30 min orbit time adjustment Uncertainty model

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

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 Assessment of stability ARC - Tropical Moored Buoys

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 Pinatubo geoloc dodgy atsr2 atsr1 det. temp. drift Comparison by Nick Rayner

20 Read all About it! Journal: 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! 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: 1)Provide Basic Quality Control Information 2)Provide in situ Reference Measurements which are calibrated to recognised standards 3)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 , launched March 2002 Sun-synchronous orbit, 1030 local time daylight descending AATSR EENVISAT Europe’s largest satellite

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 3.7 & 11 only (D2*) reference retrieval N2, N3, D2, D3 offsets adj’d to D2* AATSR D2* for ATSR-2 is then consistent with AATSR N2, N3, D2, D3 offsets adj’d to D2* ATSR-2 No 3.7, so ATSR-2 D2* is ref. for offsets at end ATSR-1 D2* (untied) is ref. at start Detector temp. trend ATSR-1 AATSR-ATSR2 overlap Adjusted BT calibration for 3.7 & 11 (accounting for spectral responses) ATSR-2-ATSR-1 overlap Reconcile 11 & 12 BTs

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