What can we learn from European continuous atmospheric CO2 measurements to quantify regional fluxes – Part 2: Sensitivity of flux accuracy to inverse setup C. Carouge1, P. J. Rayner1, P. Peylin1,2, P. Bousquet1,3, F. Chevallier1, and P. Ciais1 1Laboratoire des Sciences du Climat et de l'Environnement, UMR1572, CNRS-CEA-UVSQ, Bât. 701, Orme des Merisiers, 91191 Gif-sur-Yvette, France 2Laboratoire de Biogéochimie et Ecologie des Milieux Continentaux, CNRS-UPMC-INRA, Paris, France 3Université de Versailles Saint-Quentin en Yvelines, Versailles, France
Abstract. An inverse model using atmospheric CO2 observations from a European
network of stations to reconstruct daily CO2 fluxes and their
uncertainties over Europe at 50 km resolution has been developed within a
Bayesian framework. We use the pseudo-data approach in which we try to
recover known fluxes using a range of perturbations to the input. In this
study, the focus is put on the sensitivity of flux accuracy to the inverse
setup, varying the prior flux errors, the pseudo-data errors and the network
of stations. We show that, under a range of assumptions about prior error
and data error we can recover fluxes reliably at the scale of 1000 km and
10 days. At smaller scales the performance is highly sensitive to details of
the inverse set-up. The use of temporal correlations in the flux domain
appears to be of the same importance as the spatial correlations. We also
note that the use of simple, isotropic correlations on the prior flux errors
is more reliable than the use of apparently physically-based errors.
Finally, increasing the European atmospheric network density improves the
area with significant error reduction in the flux retrieval.
Citation: Carouge, C., Rayner, P. J., Peylin, P., Bousquet, P., Chevallier, F., and Ciais, P.: What can we learn from European continuous atmospheric CO2 measurements to quantify regional fluxes – Part 2: Sensitivity of flux accuracy to inverse setup, Atmos. Chem. Phys., 10, 3119-3129, doi:10.5194/acp-10-3119-2010, 2010.