Articles | Volume 12, issue 10
Atmos. Chem. Phys., 12, 4493–4512, 2012

Special issue: POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface...

Atmos. Chem. Phys., 12, 4493–4512, 2012

Research article 22 May 2012

Research article | 22 May 2012

Assimilation of IASI satellite CO fields into a global chemistry transport model for validation against aircraft measurements

A. Klonecki1, M. Pommier2,*, C. Clerbaux2,3, G. Ancellet2, J.-P. Cammas4, P.-F. Coheur3, A. Cozic5, G. S. Diskin6, J. Hadji-Lazaro2, D. A. Hauglustaine5, D. Hurtmans3, B. Khattatov7, J.-F. Lamarque7, K. S. Law2, P. Nedelec4, J.-D. Paris5, J. R. Podolske8, P. Prunet1, H. Schlager9, S. Szopa5, and S. Turquety10 A. Klonecki et al.
  • 1NOVELTIS, Ramonville-Saint-Agne, France
  • 2UPMC Univ. Paris 06; Université Versailles St-Quentin; CNRS/INSU, LATMOS-IPSL, Paris, France
  • 3Spectroscopie de l'Atmosphère, Chimie Quantique et Photophysique, Université Libre de Bruxelles (ULB), Brussels, Belgium
  • 4Université de Toulouse, CNRS, UMR5560, Laboratoire d'Aérologie, Toulouse, France
  • 5LSCE/IPSL, CEA-CNRS-UVSQ, Saclay, France
  • 6NASA Langley Research Center, MS 483, Hampton, USA
  • 7National Center for Atmospheric Research, Boulder, Colorado, USA
  • 8NASA Ames Research Center, Moffett Field, California, 94035, USA
  • 9DLR, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 10UPMC Univ. Paris 06; Ecole Polytechnique; CNRS UMR 8539, LMD-IPSL, Palaiseau, France
  • *now at: Air Quality Research Division, Science and Technology Branch, Environment Canada, Toronto, Ontario, Canada

Abstract. This work evaluates the IASI CO product against independent in-situ aircraft data from the MOZAIC program and the POLARCAT aircraft campaign. The validation is carried out by analysing the impact of assimilation of eight months of IASI CO columns retrieved for the period of May to December 2008 into the global chemistry transport model LMDz-INCA. A modelling system based on a sub-optimal Kalman filter was developed and a specific treatment that takes into account the representativeness of observations at the scale of the model grid is applied to the IASI CO columns and associated errors before their assimilation in the model. Comparisons of the assimilated CO profiles with in situ CO measurements indicate that the assimilation leads to a considerable improvement of the model simulations in the middle troposphere as compared with a control run with no assimilation. Model biases in the simulation of background values are reduced and improvement in the simulation of very high concentrations is observed. The improvement is due to the transport by the model of the information present in the IASI CO retrievals. Our analysis also shows the impact of assimilation of CO on the representation of transport into the Arctic region during the POLARCAT summer campaign. A considerable increase in CO mixing ratios over the Asian source region was observed when assimilation was used leading to much higher values of CO during the cross-pole transport episode. These higher values are in good agreement with data from the POLARCAT flights that sampled this plume.

Final-revised paper