Atmos. Chem. Phys. Discuss., 9, 1521-1560, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
A modelling study of photochemical regimes over Europe: robustness and variability
M. Beekmann1 and R. Vautard2
1Laboratoire Inter-Universitaire des Systèmes Atmosphériques, Créteil, France
2Laboratoire de Sciences du Climat et de l'Environnement, CEA/CNRS/UVSQ, Gif/Yvette, France

Abstract. The variability of the relative sensitivity to volatile organic compounds (VOC) or NOx emissions, the chemical regime, over Europe during summers 2001 to 2003 is simulated with a regional scale transport-chemistry model. The robustness of chemical regimes is shown. A VOC sensitive regime over North-Western Europe and a mainly NOx sensitive regime over the Mediterranean basin and Eastern Europe are found, confirming earlier published results. The chemical regime time variability, its robustness to several environmental factors (seasonality, interannual variability) and to model uncertainty are thoroughly analysed. The chemical regime spatial structure only slightly depends on the ozone target considered (daily ozone maximum or AOT40, SOMO35, ...). Differences between particular years and summer months are weak. Day to day variability is significant but does not change the occurrence of one or another chemical regime over North-Western Europe and the Mediterranean basin. Expected decreases in anthropogenic NOx emissions over Europe since the last and for the next few decades have shifted and will shift chemical regimes to more NOx sensitive. The predictive and explanatory use of chemical regime indicator species is also investigated. For all cases but near ship tracks over the Mediterranean basin, the spatial pattern of chemical regimes appears to be robust with respect to model uncertainty.

Citation: Beekmann, M. and Vautard, R.: A modelling study of photochemical regimes over Europe: robustness and variability, Atmos. Chem. Phys. Discuss., 9, 1521-1560, doi:10.5194/acpd-9-1521-2009, 2009.
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