1. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 1/24 Collocation Error budget Vertical Horizontal Perspectives ISSI WG on Atmospheric Water Vapour MULTI-DIMENSIONAL CHARACTERISATION OF INFORMATION CONTENT FROM SATELLITES ISSI WG on Atmospheric Water Vapour MULTI-DIMENSIONAL CHARACTERISATION OF INFORMATION CONTENT FROM SATELLITES Jean-Christopher LAMBERT and Coralie DE CLERCQ Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, BE

2. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 2/24 Collocation Error budget Vertical Horizontal Perspectives 1. Rationale 2. What is a collocation? 3. What is a good collocation? (error budget) 4. Vertical issues 5. Horizontal issues 6. Perspectives ISSI WG on Atmospheric Water Vapour MULTI-DIMENSIONAL CHARACTERISATION OF INFORMATION CONTENT FROM SATELLITES ISSI WG on Atmospheric Water Vapour MULTI-DIMENSIONAL CHARACTERISATION OF INFORMATION CONTENT FROM SATELLITES

3. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 3/24 Collocation Error budget Vertical Horizontal Perspectives Collocation What is a "collocation" ? Illustration: Air masses addressed by Envisat, by NDACC- type instrumentation (FTIR, MWR, sonde, UVVIS), and by models and assimilation systems Typical model grid 2.5° x 5° x 1km H2OH2O

4. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 4/24 Collocation Error budget Vertical Horizontal Perspectives Collocation What is a collocation? Illustration 2: Air masses addressed by MIPAS/Envisat and by models and assimilation systems Model grid 2.5° x 5°

5. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 5/24 Collocation Error budget Vertical Horizontal Perspectives What is a collocation? Illustration 2: Air masses addressed by MIPAS/Envisat Collocation LIMB SEQUENCES START ON FIXED LATITUDE CIRCLES Data courtesy: Q. Errera and the BASCOE Team (http://bascoe.oma.be)http://bascoe.oma.be (NEARLY) ALONG-TRACK, BACKWARD NARROW FIELD OF VIEW

6. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 6/24 Collocation Error budget Vertical Horizontal Perspectives Error budget S 2 vs. 1 = S M2 + S M1 Measurement + S B2 + S B1 Measurement parameters + ( I – A 2 ) S A2 ( I – A 2 ) t Retrieval parameters + ( I – A 1 ) S A1 ( I – A 1 ) t + (A V2 – A V1 ) S XV (A V2 – A V1 ) t Vertical smoothing error + (A H2 – A H1 ) S XH (A H2 – A H1 ) t Angular smoothing error + S  t H 2 O.dt +   H 2 O.d  ) Time/space mismatch errors Rodgers, 1976, 2000 Lambert, 2006 What is a good "collocation"? Error budget of a comparison of remotely sensed data (principle also applicable to data assimilation)

7. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 7/24 Collocation Error budget Vertical Horizontal Perspectives  A "good collocation" for comparing and combining Atmospheric Composition data is:  Temporal and geographical mismatch smaller than individual uncertainties  Small difference in vertical/horizontal smoothing OR small vertical/horizontal atmospheric variability => comparison error due to smoothing differences smaller than individual uncertainties What is a good "collocation"? Error budget of a comparison of remotely sensed data (principle also applicable to data assimilation) Error budget

8. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 8/24 Collocation Error budget Vertical Horizontal Perspectives Vertical Information content aspects A G K Averaging kernels show how the system smoothes departures from the linearisation point. They are much more than weighting functions !  Using AK is not just a painless convolution !  Correct use of AK varies with the retrieval technique.  AK units? Altitude grid? Relative or absolute AK?  Comparisons: There are many ways to degrade high vertical resolution. Using AK reduces the smoothing error, but at the detriment of independency.

9. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 9/24 Collocation Error budget Vertical Horizontal Perspectives Vertical © 2005 GOME OPERA R2 AK data courtesy KNMI (Mijling and Tuinder) Information content aspects Vertical averaging kernels for GOME ozone profiling

10. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 10/24 Collocation Error budget Vertical Horizontal Perspectives Information content aspects A G K The retrieved profile always is a mix of a priori information/constraints (G, K, S, x a ) and of measurement, in variable proportions.  Identification of information really contributed by the measurement?  Comparison-based applications, e.g. validation and data assimilation: how far are comparisons meaningful?  Geophysical interpretation: where do the "observed" signals (trends, structure etc.) come from? Vertical

11. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 11/24 Collocation Error budget Vertical Horizontal Perspectives Long-term degradation Illustration: nadir ozone profiling with GOME 1997 © 2005 GOME OPERA R2 data courtesy KNMI (Mijling and Tuinder) New (improved) version R4 publicly available Vertical

12. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 12/24 Collocation Error budget Vertical Horizontal Perspectives Long-term degradation Illustration: nadir ozone profiling with GOME 1997 Vertical

13. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 13/24 Collocation Error budget Vertical Horizontal Perspectives Global structures Illustration: nadir ozone profiling with GOME © 2005 GOME OPERA R2 data courtesy KNMI (Mijling and Tuinder) New (improved) version R4 publicly available Vertical

14. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 14/24 Collocation Error budget Vertical Horizontal Perspectives Horizontal What is a collocation? SAUNA Campaigns: High ozone and low Sun in the Arctic spring Preliminary results © SAUNA campaign

15. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 15/24 Collocation Error budget Vertical Horizontal Perspectives Dumont d’Urville (French Antarctica, 66°S / 140°E) Tarawa (Kiribati, 1°N / 173°E) What is a collocation? Horizontal smoothing error: Ozone in the Equatorial Pacific and in Antarctica Horizontal

16. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 16/24 Collocation Error budget Vertical Horizontal Perspectives Impact on satellite validation Illustration 2: Total NO2 by GOME and by the NDACC 500km radius: SAA + pollution © NDACC SAOZ data courtesy CNRS/UNESP Horizontal

17. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 17/24 Collocation Error budget Vertical Horizontal Perspectives Impact on satellite validation Illustration 2: Total NO2 by GOME and by the NDACC matching of optical paths : SAA mainly © NDACC SAOZ data courtesy F. Goutail (CNRS) and G. Held (UNESP) Horizontal

18. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 18/24 Collocation Error budget Vertical Horizontal Perspectives MIPAS Horizontal Smoothing

19. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 19/24 Collocation Error budget Vertical Horizontal Perspectives MIPAS Horizontal Smoothing

20. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 20/24 Collocation Error budget Vertical Horizontal Perspectives MIPAS Horizontal Smoothing

21. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 21/24 Collocation Error budget Vertical Horizontal Perspectives Horizontal Impact on satellite validation Illustration 2: Error budget of MIPAS T and O3 validation SYSTEMATIC RANDOM T O3

22. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 22/24 Collocation Error budget Vertical Horizontal Perspectives Impact on satellite validation Illustration 2: MIPAS T and O3 validations Horizontal

23. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 23/24 Collocation Error budget Vertical Horizontal Perspectives Impact on satellite validation Illustration 2: MIPAS T and O3 validations Horizontal

24. ISSI WG on H 2 O Bern, Switzerland Feb. 11-14, 2008 Information Content from Satellites 24/24 Collocation Error budget Vertical Horizontal Perspectives  What is missing in many comparisons/integrations is a complete error budget. This should include estimates of natural variability as probed by the different kinds of instrumentation.  No once-and-for-all solution or method. The work to be done depends on the observation technique, the intended use etc.  EC FP6 IP GEOMon [www.geomon.eu] European networks, 4 themes Improved integration of GB and satellite data BIRA-IASB, IMK/FZK, INSU/CNRS (+ assimilation teams): Studies of integration tools in support to geophysical interpretation, validation and assimilation Conclusion and perspectives