Future Local-Scale Extreme Precipitation Changes in Norway: A Convection-Permitting Climate Model Perspective

Building on previous work demonstrating the skill of high-resolution Convection-Permitting Regional Climate Models in simulating extreme precipitation at local to regional scales, this study explores future projections of hourly and daily extreme precipitation across Norway. We use data from the HARMONIE-Climate (HCLIM) model applied at 12 and 3 km resolutions and examine the extreme precipitation response by the middle and end of the century in the RCP8.5 emission scenario. Our results show that: (a) precipitation intensity is projected to increase across almost all regions, except for daily extremes from HCLIM models driven by EC-EARTH global climate model (GCM) in the southern and south-western regions. HCLIM simulations driven by GFDL-CM3 GCM project a larger increase in extremes compared with those driven by EC-EARTH, which is likely associated with the stronger warming and moistening seen in GFDL-CM3 over northern Europe in this scenario. (b) Frequency of both hourly and daily extremes is projected to increase in the future. However, the seasonality of extremes does not exhibit a shift, except for hourly extremes in the western region shifting from autumn-winter to spring-summer, and southern region shifting from spring-summer to autumn-winter. (c) Convection-permitting simulations (∼3 km grid spacing) show a larger increase in extreme precipitation at both daily and hourly timescales across most seasons except winter while also projecting a comparable increase in the frequency of extreme events to convection-parameterized models (∼12 km) in most regions. This study highlights the critical role of high-resolution modeling in credibly capturing the local-scale spatiotemporal changes in extreme precipitation.