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

Abstract. Heatwaves are among the most impactful climate extremes in Europe. Their recurrence, defined as sequences of heatwaves separated by short breaks, is projected to increase disproportionately under climate change, yet remains poorly understood. This is in part because recurrence emerges from interacting processes operating across spatial scales, from local land–atmosphere feedbacks to large-scale atmospheric 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 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, recurrent heatwave objects, defined as spatially contiguous heatwave objects corresponding to strong local recurrence, show higher soil moisture depletion and higher temperatures compared to single events. They further persist longer, cover larger areas, and are more frequently associated with European blocking in July and August. Continental recurrence reflects summers in which multiple heatwave objects overlap spatially, 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, despite some overlap between high continental and high local recurrence, both represent distinct and complementary perspectives on heatwave recurrence.

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.