Climatology and Northern winter variability of the middle atmosphere modelled with UA-ICON (NWP)

The ICON model with upper atmosphere extension (UA-ICON) running with the Atmosphere in the Earth System (AES) physics package suffers from a weak stratospheric polar vortex, though this package is intended for simulations of ICON on the seasonal to climatological time scales. For example, UA-ICON (AES) data from model free runs predict an unrealistically high number of SSWs per decade. However, due to the weak polar vortex, the simulated SSWs are of too weak intensity concerning the polar cap averaged temperature and mid-latitude zonal mean, zonal wind anomalies compared to observations. The climatology and variability of the Northern hemispheric (NH) stratospheric winter circulation widely improve when applying ICON and UA-ICON with the physics package for numerical weather prediction (NWP). However, whereas the NWP physics package is implemented technically for UA-ICON, it is not well-tuned for the upper mesosphere/ lower thermosphere (UMLT) region. This concerns, e.g. the temperatures in the summer mesopause regions at both hemispheres, which are much too warm, or the zonal mean wind structures in the lower thermosphere, which do not show the wind reversals from westerly to the easterly zonal wind in winter and vice versa in summer. These problems are caused mainly by an underrepresentation of the non-orographic gravity wave drag (NGWD), implemented with the parametrization based on Warner and McIntyre. The orographic gravity wave drag (OGWD) implemented with a parametrization based on Lott and Miller acts mainly in the stratosphere, but OGWD tuning also influences temperatures in the mesopause.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)