Unprecedented Extreme Meteorological Droughts Simulated in Fenno-Scandinavia with High-Resolution Climate Models

Convection-permitting regional climate models (CPRCMs) increasingly model local climate at scales smaller than 4 km. CPRCMs provide improved simulations of precipitation by resolving convection explicitly instead of relying on parameterisation.Still, CPRCMs' implications for drought conditions remain underexplored, especially in Europe and Fenno-Scandinavia where future changes in drought frequency and intensity are still unclear.In this study, we use data from a recent CPRCM run based on HARMONIE-Climate over Fenno-Scandinavia at approximately 3 km resolution to assess changes in drought probabilities in Fenno-Scandinavia using the Standardized Precipitation Index (SPI). Therefore, we developed a more nuanced multi-threshold method, analysing the previously overlooked different intensities of droughts.We found that overall there will be fewer future months with moderate drought. However, the number of months with extraordinary and unprecedented drought levels will increase, especially during the growing season. Both the CPRCM and the regional climate models (RCM) demonstrate this signal. The CPRCM is projecting more droughts compared to the RCM, especially for the most intense drought intensities.According to the data in this study, large parts of Fenno-Scandinavia will be affected by droughts of unprecedented intensities by the middle and especially by the end of the 21st century.Our findings show the potential of using CPRCMs for modelling drought, as the more accurate physical representation of precipitation manifests in an increased frequency of drought projections compared to RCM. Furthermore, we recommend the use of the multi-threshold method to better capture the complexity of droughts in a changing climate.