Model Development Simulation of variability in atmospheric carbon dioxide using a global coupled Eulerian – Lagrangian transport model

Abstract. This study assesses the advantages of using a cou-pled atmospheric-tracer transport model, comprising a global Eulerian model and a global Lagrangian particle dispersion model, to improve the reproducibility of tracer-gas varia-tions affected by the near-field surface emissions and trans-port around observation sites. The ability to resolve vari-ability in atmospheric composition on an hourly time-scale and a spatial scale of several kilometers would be beneficial for analyzing data from continuous ground-based monitoring and from upcoming space-based observations. The coupled model yields an increase in the horizontal resolution of trans-port and fluxes, and has been tested in regional-scale stud-ies of atmospheric chemistry. By applying the Lagrangian component to the global domain, we extend this approach to the global scale, thereby enabling computationally efficien