Future changes in sub-daily extreme areal precipitation and their temperature scaling in the Great Alpine Region

Sub-daily precipitation extremes are a primary trigger of flash floods and debris flows in the Great Alpine Region, yet their future evolution is still uncertain, especially in relation to changes at the catchment scale. Recent work using convection-permitting ensembles has demonstrated added value and different change signals relative to the Regional Climate Models (RCMs) that drive them, but most analyses remain focused on grid-point indices. This study addresses this gap by focusing on areal rather than local precipitation. It provides a unified comparison of Convection Permitting Models (CPMs) and RCM projections of areal extremes, together with a temperature-scaling framework to provide a physical interpretation of the projected changes.

We use the CORDEX-FPS kilometer-scale CPMs and their driving regional climate models to assess changes in areal extreme precipitation between a historical (1996–2005) and far-future (2090–2099) period under the RCP8.5 emission scenario. We quantify projected changes in extreme precipitation across durations from sub-daily to daily and across spatial scales up to 5000 km². We directly compare the change signals from CPMs against those from their driving RCMs. To understand the physical mechanisms behind these changes, we analyse precipitation-temperature scaling relationships, diagnosing where they follow thermodynamic expectations (Clausius-Clapeyron-like scaling) versus where they deviate from those, pointing to more dynamical controls across spatial scales.