Atmospheric Dynamics Reduce Mid-latitude Heatwave Frequency under Idealized Climate Change Forcing

Abstract. Recent decades have seen a global increase in hot temperature extremes, yet the role of changes in the atmospheric circulation in driving this trend remains unclear. To better understand how atmospheric dynamics control extreme weather, we explore a mechanism that relates mid-latitude heatwave frequency to the storm track position in a suite of idealized model experiments with the dry dynamical core of the ICON model. The underlying relationship between the zonal phase speed of synoptic-scale waves, the latitude of the storm track, and the strength of the eddy-driven jet is assessed through spectral analysis of upper-tropospheric meridional wind. By comparing our experiments to reanalysis data, we find evidence that observed trends in the Southern Hemisphere circulation have contributed towards reducing the persistence of austral mid-latitude hot temperature extremes. This mechanism may also be relevant for the future evolution of extreme events in the Northern Hemisphere, where we see the joint influence of Arctic Amplification and the expansion of the tropics.