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Abstract

Heatwaves, defined as extended periods of excessive heat, are one of the most hazardous weather events, with important implications for human health, the economy and infrastructure. The time needed to prepare for an extreme weather event is often on the order of several weeks to months, well beyond the current reliability of short-term weather predictions. In this project, we aim to enhance the predictability of heatwaves at lead times of weeks to months by allowing for an improved understanding of their fundamental drivers. This will be achieved by building a model hierarchy of increasing complexity of the general circulation model ICON. The hierarchy includes model versions starting from the ICON dry dynamical core to the full model physics, to investigate specific mechanisms of potential relevance for the representation of heatwaves at the different steps of the hierarchy. Here we present the preliminary results of the project. These include a set of experiments with the dry dynamical model core, showing that mountains located along the midlatitude jet axis have the largest impact on heatwaves and that changes in surface roughness length affect the intensity and the position of the jet, with important consequences for the occurrence of heatwaves, particularly over the mid-to-high latitudes. Additionally, we present a series of experiments testing the effect of local changes to different features of a Mixed-Layer Ocean, as well as an evaluation of the ability of the ICON version with full model physics in reproducing heatwave events as derived from reanalysis data.