Abstract
The Norwegian Water Resources and Energy Directorate (NVE) has an ambition of introducing energy balance snow melt modelling in their hydrological models, preferably on a finer resolution than daily in order to account for diurnal variations. In that context the physically based point energy balance model seNorge eb, with precipitation and temperature as input data, was evaluated on 3 and 24 hour resolution in terms of its precision in predicting snow melt rates. Simu- lated snow melt rates during the main ablation season in April/May were evaluated against observed values from NVEs snow research station at Filefjell. Simulated radiation components and variables were compared with observed radiation and meteorological data. Parametrizations and variables in seNorge eb were, one at the time, replaced with observed data, with the aim of deciding the minimum input data requirement. In terms of the overall model performance, both the 3 and 24 hour resolution versions performed well in predicting snow melt rates, with the best results on 24 hour resolution. From the analysis of the individual components, deviations between simulated and observed data were identified. The cloud cover fraction was found to be a main source of error and the component most urgent to correct as it is embedded both in the incoming solar radiation and atmospheric long- wave radiation, the most important energy sources for snow melt. The clear- sky atmospheric emissivity was found as another source of error in the simulated atmospheric long-wave radiation. Local calibration of the clear-sky atmospheric emissivity may be worth testing. Regarding the minimum input data requirement, relative humidity is recommended as additional input data for both resolutions, in addition to wind and snow surface temperature on 3 hour resolution. seNorge eb, as it is set up today, should not be implemented in a hydrological model. For that to happen, the model s problem areas have to be improved, in particular the cloud cover fraction and the parametrization of the atmospheric long-wave radiation.