Snowfall Limit Forecasts and Hydrological Modeling

Hydrological flood forecasting in mountainous areas requires accurate partitioning between rain and snowfall to properly estimate the extent of runoff contributing areas. Here a method to make use of snowfall limit information-a standard output of limited-area models (LAMs)-for catchment-scale hydrological modeling is proposed. LAMs consider the vertical, humid, atmospheric structure in their snowfall limit calculations. The proposed approach is thus more physically based than inferring snowfall limit estimates based on (dry) ground temperature measurements, which is the standard procedure in most hydrological models. The presented case study uses forecast reanalyses from the Consortium for Small-Scale Modeling (COSMO) limited-area model as input for discharge simulation in a topographically complex catchment in the Swiss Alps. Results suggest that the use of COSMO snowfall limits during spring snowmelt periods can provide more accurate runoff simulations than routine procedures, with practical implications for operational hydrology in Alpine regions.