Rain-on-snow events in mountainous catchments under climate change

Abstract. The frequency and intensity of rain-on-snow (RoS) events are expected to change in response to climate variations due to changes in precipitation, increases in air temperature, and subsequent changes in the snow cover. In this study, we attributed these changes to the simulated variations in RoS events using a sensitivity analysis of precipitation and air temperature and subsequent effects on RoS-related runoff responses. We selected 93 mountainous catchments located in central Europe across Czechia (60), Switzerland (26), and Germany (7) and used a conceptual hydrological model to simulate runoff components for 24 climate perturbations relative to the reference period 1980–2010. Climate change-driven RoS changes were highly variable over regions, across elevations, and within the cold season. The warmest perturbations suggested a decrease in RoS days by about 75 % for the Czech catchments. In contrast, the Swiss catchments may respond less sensitively, with the number of RoS days even increasing, specifically during winter and at higher elevations. Our results also suggested that the RoS contribution to annual runoff will be considerably reduced from the current 10 % to 2 %–4 % for the warmest perturbations in Czechia and from 18 % to 5 %–9 % in Switzerland. However, the RoS contribution to runoff may increase in winter months, especially for perturbations, leading to an increase in precipitation and demonstrating the joint importance of air temperature and precipitation for future hydrological behaviour in snow-dominated catchments.