How atmospheric and surface conditions shape recurrent heatwaves in Europe: From local to continental scale

Heatwaves are among the most impactful climate extremes in Europe. Their recurrence, defined as sequences of heat events separated by short breaks, is projected to increase disproportionately under climate change. Yet the physical drivers of recurrent heatwaves remain poorly understood, partly because recurrence emerges from interacting processes operating across spatial scales, from local land–atmosphere feedbacks to large-scale circulation, and studies often focus on only one scale at a time. We develop a unified framework to investigate heatwave recurrence across local, object, and continental scales over Europe using the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis for 1950–2024. 

Our preliminary results reveal complementary insights at each spatial scale. Local recurrence, that is heatwaves at one location separated by less than seven days, exhibit weaker daily temperature and soil moisture anomalies than isolated events. However, heatwave object recurrence, defined as spatially contiguous heatwave objects generating strong local recurrence, shows higher soil moisture depletion and higher temperatures compared to single events. They further persist longer and are associated with distinct atmospheric circulation regimes. Continental recurrence reflects summers in which multiple heatwave objects overlap, affecting large areas or striking the same regions repeatedly. It emerges as a distinct dimension of summer heat extremes rather than simply reflecting anomalously warm conditions. Summers with high continental recurrence feature more heatwaves, larger affected areas, higher temperature anomalies, and earlier, more persistent soil moisture depletion compared to summers with isolated events. Further, high continental recurrence is strongly related to the occurrence of locally recurrent events.

These findings demonstrate that recurrence is a cross-scale phenomenon and highlight the importance of integrating complementary spatial perspectives to better understand compound heat extremes and the coupled atmospheric–land surface processes that govern them.