Modelling and validation of small-scale variability of the MLTI using WACCM-RR over Scandinavia

The ability of Earth system models to forecast the behaviour of the mesosphere/lower thermosphere/ionosphere (MLTI) system lags far behind that of other atmospheric regions, hindering prediction capability of the whole atmosphere. A better understanding of the nature and causes of MLTI variability, which is currently poorly understood, can address this problem. In this work we present results from the Whole Atmosphere Community Climate Model with regional refinement (WACCM-RR) which has been employed to resolve what would normally be subgrid-scale gravity waves that give rise to variability on timescales from hours to days and length scales from several to several hundred kilometres. We focus our studies over high-latitude Scandinavia, the most instrumented region on Earth for MLTI studies, where we resolve down to 1/8° horizontal resolution, approximately 14 km, and study small-scale variability of temperature, horizontal/vertical winds, electron density and key atmospheric constituents such as O, NO and O₃. The modelled variability is compared to WACCM simulations without regional refinement (global 1° resolution) and observations from instruments over Scandinavia such as EISCAT, NIPR and AMTM. This study will allow us to identify in-situ and external variability drivers and correlate them to local and global processes and coupled interactions between the atmospheric layers. This work is thus a step towards determining predictable variability of small-scale features in the MLTI, pushing beyond current limitations in forecasting the whole atmosphere.