*2.1. Reference Data*

WATCH Forcing Data based on ERA-Interim reanalysis (WFDEI) is used as the reference climatology in real-world illustrations as well as in hydrological modeling exercises for both daily mean temperature and precipitation [27]. In this data set the monthly means of daily mean temperature and precipitation have been adjusted for biases in relation to the large scale gridded observations produced by the Climatic Research unit (CRU) and the Global Precipitation Climatology Centre (GPCC) with subsequent elevation corrections applied to both variables. Rust et al. [28] discuss some of the known issues in WFDEI such as spurious jumps between individual months caused by the bias adjustment procedure. These introduced discontinuities might affect the hydrological simulations, for example, by triggering snow melt unrealistically. However, the effect of the spurious jumps is less severe in the European region than in the tropics and cold regions [28], which facilitates the use of WFDEI in this study.
