CMIP7 solar forcing – evaluation of solar impacts with UA-ICON

The ICOsahedral Non-hydrostatic model (ICON) framework is the open-source numerical weather prediction and climate model jointly developed by the German Weather Service (DWD), the Max-Planck Institute of Meteorology (MPI-M), Deutsches Klimarechenzentrum (DKRZ), the Karlsruhe Institute of Technology (KIT), and the Center for Climate Systems Modeling (C2SM). A consolidated climate setup with interactive ocean, land surface and atmosphere is being developed and tested. However, while ICON's basic setup includes monthly varying solar TSI and SSI forcing, the ability to prescribe higher-frequency UV irradiances and energetic particle precipitation (EPP) to change atmospheric composition has not been considered.

The upper atmosphere extension of ICON (UA-ICON) is currently a modelling framework allowing the analysis of dynamic phenomena from the ground to the lower thermosphere (150 km). Implementing varying solar forcing and interactive chemistry is expected to hugely influence the thermal structure and composition in the mesosphere/lower thermosphere (MLT).

Updated historical forcing datasets for the 7th phase of the Coupled Model Intercomparison Project (CMIP7) are now available for evaluation. These include daily varying spectral solar irradiance (SSI), total solar irradiance (TSI), and ion pair production rates for solar protons, cosmic rays, and medium-energy electrons to model EPP. Implementing these solar forcing data and the interactive chemistry is still ongoing work, and we present the first results of this effort, focusing on the MLT and UA-ICON.