The new online-coupled chemistry transport model ICON-MUSCAT: First applications and validation

The chemistry transport model MUSCAT (Wolke et al., 2012), was coupled to the numerical weather prediction (NWP) model ICON of German Weather Service (DWD, Zängl et al., 2015). MUSCAT was previously already coupled to COSMO, the former NWP model of DWD. Since with ICON, not only the horizontal grid structure (icosahedral grid consisting of triangles) did change, but also the whole code structure. Hence, the coupling required more steps than previous updates of COSMO, both for ensuring efficiency and flexibility of the model simulations and easy further updates.

With the two model versions, COSMO-MUSCAT and ICON-MUSCAT, the whole year 2019 was simulated over Europe. Results with COSMO-MUSCAT are already published by Thürkow et al., 2024. The presentation therefore focuses on the validation of ICON-MUSCAT and a comparison to the performance of the predecessor model version. For this purpose, we utilize data of European air quality monitoring stations provided by the European Environmental Agency (EEA). The model is validated according to FAIRMODE (Janssen and Thunis, 2022) standards. Overall, ICON-MUSCAT performs well and similarly as with the previous meteorological driver. Differences between the two model versions were found related to boundary layer physics. For example, the ozone deposition was found to be sensitive to the surface temperature, which leads to night-time differences between the two model version for the ground-level ozone concentration. The comparison to traffic-related observations of NO₂ concentrations in urban locations and to traffic counts suggest a revision of the prescribed emission profiles of the traffic-sector (CAMS-TEMPO, Guevara et al., 2021) as in particular morning emission peaks were simulated earlier than in occurring in the observations. In addition, different available emission inventories (amongst others CAMS, EDGAR, CEDS) were investigated to analyze the uncertainty due to the choice of emission inventory.

 

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