Future Changes in Severe Frontal Precipitation Events over Europe and Their Drivers

Abstract. Atmospheric fronts are closely linked to extreme precipitation across the mid-latitudes, which is projected to intensify in many regions under global warming. Understanding the physical drivers of these changes is essential to improve confidence in climate projections. Here, we analyze projected changes in seasonal heavy and extreme frontal precipitation events over Europe using the CMIP6 and EURO-CORDEX ensembles, combining event frequency analysis with frontal composite cross-sections to assess the changes of the underlying thermodynamic and dynamic processes. We find that the number of heavy frontal precipitation events increases by up to 50 % per degree of global warming, while extreme events are projected to more than double per degree. Large-scale circulation changes account for most regional reductions in frontal extremes, but contribute only weakly to the widespread increases. Thermodynamic changes, however, dominate the intensification of extremes. Increases in specific humidity are the primary driver of more intense events, while changes in the frontal circulation are minimal, likely because a more stable atmosphere counteracts potential strengthening from enhanced latent heat release.