Do convection-permitting regional climate models have added value for hydroclimatic simulations? A test case over small and medium-sized catchments in Germany

Abstract. Through fine grid structure and explicit representation of deep convective processes, convection-permitting regional climate models (CPRCMs) bear great potential for improved assessment of climate and hydrology under current and future climatic conditions. For a robust assessment of the added value of CPRCMs as climate service for hydrological impact modelling, the current scope of research needs to be expanded by studies on further model structures and study areas. The paper presented here considers the non-hydrostatic model ICON-CLM 2.6.4 at 3 km resolution (ICON3km) and its driving model ICON-CLM 2.6.4 with parametrised convection at 11 km (ICON11km) for a study area of 13,210 km² in East Central Germany, enclosing the small (107 km²) to medium-sized (529 km²) catchments of the upper and central part of the predominantly rural Weiße Elster river basin. The reanalysis-driven historical hourly air temperature, global radiation, relative humidity, wind speed and precipitation simulations are evaluated. ICON3km is further analysed for added value for discharge simulations using the distributed hydrological model WaSiM. Our results suggest primarily an improvement by ICON3km in the estimation of summer air temperature and global radiation, as well as reducing the overestimation of the left tail of the frequency distribution of wind speed. The most noticeable deficiencies of ICON3km are the strong overestimation of high precipitation intensity and too frequent heavy rainfall events. These shortcomings translate into a pronounced overestimation of discharge when uncorrected, dominating the hydrological estimations. As such, no added value in the use of ICON3km for hydrological impact modelling in the Weiße Elster basin was identified.