Le couplage dynamiquechimique en assimilation: Compte rendu du contrat avec l'Agence Spatiale Europe

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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 dAéronomie de Belgique
(BIRA-IASB) Dorval, Qc, H9P 1J3 Toronto,
Ont., M3H 5T4 3, avenue
Circulaire CANADA
CANADA
1180 Brussels, BELGIUM (4) York
University (5)
Institut für Meteorologie und Klimaforschung
Department of Earth and Atmospheric Science

Universität Karlsruhe 4700 Keele Street,
Toronto, Ont. M3J 1P3
Forschungszentrum Karlruhe CANADA
GERMANY
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Introduction

• 1. Ozone stratosphérique et la question
  environnementale
• 2 . Cycles dassimilations
• a) analyse dozone (avec et sans
  assimilation chimique)
• b) Impact radiatif - analyses et
  prédictabilité
• 3. Projet Bachus (Richard Ménard)

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Chapman, 1930
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Nitrogen catalytic cycle (Crutzen, 1970) NO O3
? NO2 O2 NO2 O ? NO O2 ____________________
__ Net result O O3 ? 2 O2
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Molina et Rowland(1974)
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From the WMO ozone assessment (2006)
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From the WMO ozone assessment (2006)
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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)

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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)

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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

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TOMS GEM-BACH 30 Sep. 2003
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Comparaison des prévisions avec les RAOBS.
Hemisphere Nord O-P 240 hrs
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Comparaison des prévisions avec les RAOBS.
Hemisphere Nord O-P 240 hrs
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Comparaison des prévisions avec les RAOBS.
Hemisphere Sud O-P 240 hrs
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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.

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