Towards transient aerosols in ICON-CLM - Impact of different aerosol climatologies

Within the framework of the project NUKLEUS (Actionable local climate information for Germany) first long-term simulations with COSMO 6.0 and ICON-CLM based on the latest release ICON NWP 2.6.4 have been performed. These simulations were driven by ERA5 reanalysis data, which were downscaled to the EUR-11 EURO-CORDEX grid having a resolution of about 12 km. To capture the whole EURO-CORDEX domain with the ICON-CLM, a R13B05 icosahedral grid with a shifted North pole was chosen. The simulation period covers more than two decades starting from 1981.

In our presentation we aim to study the basic behaviour of transient ICON-CLM hindcasts in “local area mode” configuration. First evaluation results showed ‘questionable’ results for specific periods. After detailed analysis for the reasons of the model deficits, sensitivity experiments were carried out with purely lateral nudging and additional upper boundary nudging for ICON but for COSMO as well. It will be shown that the integration of both models leads to comparable solutions and a comparable level of sensitivity to weaker atmospheric forcing.

Furthermore to the search for an optimal configuration / Keeping in mind a first ‘optimal’ configuration, the performance of ICON-CLM and COSMO-CLM is investigated. In addition to a standard evaluation of relevant climatological parameters, the characteristics of radiative fluxes, clouds and the water budgets are analyzed. Systematic differences as well as similarities between both model simulations will be emphasized during this presentation. We will in particular focus on the impact of different aerosol climatologies on the model's quality.