Changes in rain-on-snow events in mountain catchments in the rain-snow transition zone

A shift from snowfall to rain affecting snow storage is expected in future. Consequently, changes in rain-on-snow (ROS) events may occur. We evaluated the frequency and trends in ROS events and their runoff responses at different elevations related to changes in climate variables. We selected 40 central European mountain catchments located in the rain-snow transition zone, and used a conceptual catchment model to simulate runoff components for the period 1965-2019. The results showed large temporal and spatial differences in ROS events and their respective runoff responses across individual study catchments and elevations, with primarily an ROS increase at highest elevations and a decrease at lower elevations during spring. ROS events contributed 3-32% to the total seasonal direct runoff. The detected trends reflect changes in climate and snow variables, with an increase in air temperature resulting in the decrease in snowfall fraction and shorter snow cover period.