Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2016-132
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
19 Aug 2016
Review status
This discussion paper has been under review for the journal Geoscientific Model Development (GMD). A final paper in GMD is not foreseen.
Joint CO2 state and flux estimation with the 4D-Var system EURAD-IM
Johannes Klimpt1,2, Elmar Friese1, and Hendrik Elbern1,2 1Rhenish Institute for Environmental Research at the University of Cologne, 50931 Köln, Germany
2Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany
Abstract. This idealized regional atmospheric inversion study assesses the potential of the 4-dimensional variational (4D-Var) method to estimate CO2 fluxes and the atmospheric CO2 concentration state jointly. In order to distinguish and quantify the surface-atmosphere CO2 fluxes, combining anthropogenic CO2 emissions, photosynthesis, and respiration, we include uncertainties of initial values, which arise from highly uncertain surface fluxes and night-time transport. Therefor a new calculation of the background error standard deviation for the CO2 fluxes was developed. To suppress spurious wiggles occurring from advection, an absolute monotone advection scheme with low numeric diffusion and its adjoint has been implemented. The inversion by the EURopean Air pollution Dispersion-Inverse Model (EURAD-IM) with 5 km resolution in Central Europe is validated by synthetic half hourly measurements from eleven concentration towers. A significant improvement of the analysis is shown if initial values and CO2 fluxes are optimised jointly, compared to optimising CO2 fluxes alone, without estimating uncertainty of atmospheric concentration. We find that joint estimation of carbon fluxes and initial states requires a careful balance of the background error covariance matrices but enables a more detailed analysis of atmospheric CO2 and the surface-atmosphere fluxes.

Citation: Klimpt, J., Friese, E., and Elbern, H.: Joint CO2 state and flux estimation with the 4D-Var system EURAD-IM, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2016-132, 2016.
Johannes Klimpt et al.
Johannes Klimpt et al.

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Short summary
Atmospheric inversions optimize surface-atmosphere CO2 fluxes using CO2 concentration observations and atmospheric transport models. This study optimizes additionally the atmospheric initial concentration of CO2 jointly with the fluxes. Artificial generated observations are used to estimate limits and benefits of the used inversion method. Uncertainty of analyzed CO2 fluxes can be reduced with the joint optimization of fluxes and the atmospheric CO2 concentration.
Atmospheric inversions optimize surface-atmosphere CO2 fluxes using CO2 concentration...
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