ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-3173-2005 Daily CO<sub>2</sub> flux estimates over Europe from continuous atmospheric measurements: 1, inverse methodology Peylin P. 2 Rayner P. J. 3 4 Bousquet P. 4 Carouge C. 4 Hourdin F. 5 Heinrich P. 6 Ciais P. 4 AEROCARB contributors 1 Experimentalists that contributed to the atmospheric measurements: A. Adolphsen, F. Apadula, R. Graul, L. Haszpra, M. Ramonet, R. Santaguida, M. Schmidt Laboratoire de Biogéochimie isotopique, CNRS-UPMC-INRA, Paris, France CSIRO Atmospheric Research, Aspendale, Victoria, Australia Laboratoire des Sciences du Climat et de l’Environnement, CEA, Gif-sur-Yvette, France Laboratoire de Météorologie Dynamique, CNRS, Paris, France Laboratoire DASE/LDG, CEA, Bruyeres-le-Chatel, France 25 11 2005 5 12 3173 3186 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/5/3173/2005/acp-5-3173-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/3173/2005/acp-5-3173-2005.pdf

This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and spatial (model grid) resolution from continuous atmospheric concentration measurements. The method is designed for regional applications and for use in intensive campaigns. We apply the method to a one month inversion of fluxes over Europe. We show that the information added by the measurements depends critically on the smoothness constraint assumed among the source components. We show that the initial condition affects the inversion for 20 days, provided one has enough observing sites to constrain regional fluxes. We show that the impact of the far-field fluxes grows throughout the inversion and hence a reasonable global flux field is a prerequisite for a regional inversion.