le couplage dynamique chimique en assimilation n.
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  1. Le couplage dynamique-chimique en assimilation: Compte rendu du contrat avec l'Agence Spatiale Européenne. Partie II: Assimilation de l'ozone stratosphérique dans GEM Team Dr Richard Ménard (P.I.) (1) Dr Simon Chabrillat (3) Prof Jack McConnell (4) Dr Pierre Gauthier (1) Dr Dominique Fonteyn (3) Dr Jacek Kaminski (4) Dr Jean de Grandpré (1) M. Alain Robichaud (1) Dr Yves Rochon (2) Dr Thomas von Clarmann (5) M. Cécillien Charette (1) Dr Martin Charron (1) Dr Paul Vaillancourt (1) M. Alexander Kallaur (1) Dr Monique Tanguay (1) Dr Yan Yang (2) M. Michel Roch (1) With the participation of Paul-André Beaulieu(1), Quentin Errera(3), Sylvain Ménard(1), Mike Neish(2) , Bin He(1) and Cathy Xie(1) Environment Canada(3)Belgisch Instituut voor Ruimte-Aëronomie (1) 2121 Transcanada Highway (2) 4905 Dufferin Street Institut d’Aéronomie de Belgique (BIRA-IASB) Dorval, Qc, H9P 1J3 Toronto, Ont., M3H 5T4 3, avenue Circulaire CANADA CANADA 1180 Brussels, BELGIUM (4)York University(5) Institutfür Meteorologie und Klimaforschung Department of Earth and Atmospheric Science Universität Karlsruhe 4700 Keele Street, Toronto, Ont. M3J 1P3 Forschungszentrum Karlruhe CANADAGERMANY

  2. Introduction 1. Ozone stratosphérique et la question environnementale 2 . Cycles d’assimilations a) analyse d’ozone (avec et sans assimilation chimique) b) Impact radiatif - analyses et prédictabilité 3. Projet Bachus (Richard Ménard)

  3. Chapman, 1930

  4. Nitrogen catalytic cycle (Crutzen, 1970) NO + O3→ NO2 + O2 NO2+ O → NO + O2 ______________________ Net result: O + O3 → 2 O2

  5. Molina et Rowland(1974)

  6. From the WMO ozone assessment (2006)

  7. From the WMO ozone assessment (2006)

  8. GEM-BACH • Based on GEM-Strato (GEM 3.2.2 – PHY 4.4) • Non-orographic Gravity Wave Drag (Hines, 1997) • Correlated-K radiation scheme • Resolution : L80 120x240 with a lid at 0.1 hPa • 45 min time step • On-line & interactive ozone and water vapour • Ozone climatology: Fortuin & Kelder (1000-0.5 hPa) HALOE (0.5 – 0.1 hPa)

  9. BASCOE CTM • 57 chemical species, all advected (S-L) • Ox, HOx, NOx, ClOx, BrOx and few hydrocarbons • Source species: N2O, CH4, H2O, CFCs, HCFCs and Halons • 142 gas-phase reactions; 7 heterogeneous reactions • 52 photodissociation reactions, J interp from tables • Photochemical rates are taken from JPL-2002 • Solver generated by KPP (Sandu and Sander, ACP, 2006) • Numerical method: 3rd– order Rosenbrock • 45-min timesteps divided into sub-timesteps (can be as short as 1 μs)

  10. CMC Assimilation System • 3D-Var FGAT and 4D-var (Gauthier et al., 1999, 2007) • Use conventional meteorological observations (radiosondes, surface observations, aircraft winds, AMSU radiances) • ESA project: MIPAS observations (T, O3 , CH4, N2O, HNO3, NO2) • Observation and background error statistics: • Univariate background error covariances • Characterization of the chemistry component done with the Hollingsworth-Lönnberg method • MIPAS temperatures used as reference for the bias correction of AMSU-a stratospheric channels

  11. TOMS GEM-BACH30 Sep. 2003

  12. Comparaison des prévisions avec les RAOBS. Hemisphere Nord O-P 240 hrs

  13. Comparaison des prévisions avec les RAOBS. Hemisphere Nord O-P 240 hrs

  14. Comparaison des prévisions avec les RAOBS. Hemisphere Sud O-P 240 hrs

  15. Conclusion • The comparison of GEM-BACH prognostic ozone against MIPAS measurements shows that the chemistry module has an ozone deficit in the upper stratosphere. It increases with height from 10 hPa and reach ~15% at the stratopause. • The assimilation of ozone using MIPAS measurements produce analyses which are within observation uncertainties in all regions from 100 to 2 hPa. In the stratopause region analyses are largely weighted by the model due to the fact that the ozone photochemical lifetime is much shorter than 6 hr. • The comparison against independent measurements shows that the radiative feedback from ozone analyses contributes to improve temperature analyses globally above 3 hPa. However, the radiative impact of ozone analyses can have a negative impact in specific regions as the NH stratopause region. • The ozone radiative feedback has a significant impact on the model predictability in the lower stratosphere. At 50 hPa where ozone is dynamically driven, ozone assimilation increase the temperature predictability by ~1 day. The comparison against RAOBS in the region shows that ozone interactive forecasts also produce a smaller temperature drift in the region. Above 30 hPa, the ozone photochemical lifetime decrease rapidly and the impact of ozone assimilation is lost after several days. In this region, non-interactive forecasts have a smaller bias against RAOBS in comparison with ozone interactive forecasts.

  16. Radiative time scale (days) - August Cross-error covariance Temperature-Ozone Method: 6-hr differences (CQC) without ozone-radiation interaction with ozone-radiation interaction

  17. Dynamical and Radiative aspects