Future projections of wet and dry spells in southern Sweden: The impact of climate model resolution

This study evaluates how well five Regional Climate Model (RCM) projections at resolutions from 44 km to 3 km reproduce wet and dry spells compared with observations at six locations in Scania, southern Sweden. Future changes in general and extreme wet and dry signals were also analyzed under RCP8.5 to the end of the 21st century. Convection-permitting climate models (CPMs), operating at resolutions fine enough to explicitly resolve convective processes (< 4 km), are widely recognized to simulate precipitation characteristics more accurately than coarser models. Our results confirm that CPM AROME (3 km), outperforms coarser RCMs in representing both wet and dry spells. Future projections across all resolutions indicate increases in wet spells to the end of the century, with average daily precipitation increasing by 8–12 %. The number of wet events, their average depth, and duration also projected to increase to varying degrees. For dry spells, the annual number of dry days shows a slight increase (0–3 %). The number of dry events is projected to decrease while both the average duration and the annual maximum consecutive dry days increase. Extreme value analysis shows that extreme precipitation intensities at various accumulating durations increase over 5- to 50-year return periods, as implied by the Wet Climate Factor (WCF). The Dry Climate Factor (DCF) indicates shorter annual maximum consecutive dry days in the near future, but prolonged at the end of the century by 3–9 %. These findings corroborate with previous research and improve understanding of systematic biases across RCMs resolutions. They further suggest that CPMs offer improved reliability in projecting future variability in wet and dry conditions, with important implications for regional climate services. • The CPM demonstrates added value for reproducing dry spell metrics and sub-daily extreme precipitation compared with lower-resolution, non-convection-permitting RCMs. • Future changes in wet spells are resolution-sensitive, with higher-resolution models projecting stronger increases in depth but weaker increases in frequency. • The CPM projects the strongest increases in sub-daily precipitation extremes. • Future changes in dry spells show weak dependence on model resolution. • Models project minor changes in the length of extreme dry spells.

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