Increased intensity and frequency of extreme precipitation events in Belgium as simulated by the regional climate model MAR

Study region: Belgium Study focus: In July 2021, Western Germany, the Netherlands and Belgium were hit by extreme rainfall events of unprecedented intensity, raising concerns about future trends. To assess future trends in extreme precipitation frequency and intensity, we use the regional climate model MAR at 5-km spatial resolution to conduct climate projections until 2100. MAR is forced by a set of six CMIP6 Earth System model (ESMs) with 4 IPCC scenarios ranging from low to high-end warming. Study insights: First, an Extreme Value Analysis (EVA) is performed on bias-adjusted daily model outputs over 30-year moving windows. We find that, on average, extreme precipitation intensity rises following the Clausius-Clapeyron scaling, i.e., a 7% increase per additional degree of global warming. This trend results from a clear increase in the spread and in the modes of the extreme precipitation event distributions. Second, an EVA is performed over the complete simulated period (2015-2100). Our analyses reveal that, even under low-warming scenarios, return level maps, i.e., representing the precipitation values associated with a certain return period, are more intense than those obtained using observational data over 1951-2021. For the 21st century, the 20-year daily return level can locally reach 100 mm per day, which represents a 25%–30% increase relative to the present day. • We use the Regional Climate Model MAR at a 5-km resolution. • Extreme precipitation intensity rises following the Clausius-Clapeyron scaling. • For the 21st century, the 20-year daily return level can locally reach 100 mm per day.