Abstract
Abstract. Inverse modeling of anthropogenic and biospheric CO2 fluxes from ground-based and satellite observations critically depends on the accuracy of atmospheric transport simulations. Previous studies emphasized the impact of errors in simulated winds and vertical mixing in the planetary boundary layer, whereas the potential importance of releasing emissions not only at the surface but distributing them in the vertical was largely neglected. Accounting for elevated emissions may be critical, since more than 50 % of CO2 in Europe is emitted by large point sources such as power plants and industrial facilities. In this study, we conduct high-resolution atmospheric simulations of CO2 with the mesoscale Consortium for Small-scale Modeling model extended with a module for the simulation of greenhouse gases (COSMO-GHG) over a domain covering the city of Berlin and several coal-fired power plants in eastern Germany, Poland and Czech Republic. By including separate tracers for anthropogenic CO2 emitted only at the surface or according to realistic, source-dependent profiles, we find that releasing CO2 only at the surface overestimates near-surface CO2 concentrations in the afternoon on average by 14 % in summer and 43 % in winter over the selected model domain. Differences in column-averaged dry air mole XCO2 fractions are smaller, between 5 % in winter and 8 % in summer, suggesting smaller yet non-negligible sensitivities for inversion modeling studies assimilating satellite rather than surface observations. The results suggest that the traditional approach of emitting CO2 only at the surface is problematic and that a proper allocation of emissions in the vertical deserves as much attention as an accurate simulation of atmospheric transport.
Highlights
Predicting future atmospheric concentrations of CO2, the most important long-lived greenhouse gas, requires a profound understanding of the global carbon cycle, the contributions from anthropogenic and natural fluxes and their sensitivity to climate change, and political and societal drivers
We investigated the sensitivity of model-simulated nearsurface and total column CO2 concentrations to a realistic vertical allocation of anthropogenic emissions as opposed to the traditional approach of emitting CO2 only at the surface
The study was conducted using kilometer-scale atmospheric transport simulations for the year 2015 for a domain covering the city of Berlin and numerous power plants in Germany, Poland and Czech Republic
Summary
Predicting future atmospheric concentrations of CO2, the most important long-lived greenhouse gas, requires a profound understanding of the global carbon cycle, the contributions from anthropogenic and natural fluxes and their sensitivity to climate change, and political and societal drivers. An important tool for advancing our knowledge of the carbon cycle is the integration of CO2 observations with atmospheric transport simulations in an inverse modeling framework. Global inverse modeling systems helped to better constrain the terrestrial carbon budget, to allocate the global land sink to different continents and ecosystems, and to assess interannual variability and the sensitivity to climate variations (e.g., Bousquet et al, 2000; Chevallier et al, 2010; Peylin et al, 2013; van der Laan-Luijkx et al, 2017; Rödenbeck et al, 2018). Brunner et al.: Atmospheric CO2 simulations with vertical emissions regional scale (e.g., Sarrat et al, 2009; Goeckede et al, 2010; Broquet et al, 2011; Meesters et al, 2012)
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