Modelling climate change in the MLT with a gravity-wave permitting setup of UA-ICON

The anthropogenic emission of carbon dioxide has been attributed as the main driver of global warming. However, its radiative properties also cause the middle atmosphere to cool and contract. This cooling, as well as associated changes in large-scale circulation patterns of the troposphere and stratosphere, result in trends in the mesosphere and lower thermosphere (MLT) region. We conducted a whole-atmosphere simulation employing the ICOsahedral Non-hydrostatic general circulation model with Upper Atmosphere extension (UA-ICON) in the configuration with the numerical weather prediction (NWP) physics package. As gravity waves are the main driver of the dynamics in the MLT and thus critically influence its thermal structure, we chose a horizontal resolution of 20 km to model a large portion of the gravity wave spectrum explicitly. A realistic large-scale circulation up to 50 km is ensured by constraining the dynamics of the troposphere and stratosphere to the ECMWF Reanalysis v5 (ERA5) dataset.
From the simulation, we derive trends of the atmospheric mean circulation and temperature. Additionally, the run is analyzed within the Transformed Eulerian Mean (TEM) framework to derive trends related to gravity waves and wave-mean flow interaction. For validation, the results are compared with the Atmospheric General circulation model for the Upper Atmosphere Research-Data Assimilation System (JAGUAR-DAS) whole neutral atmosphere reanalysis dataset (JAWARA).