Estimating degree-day factors of snow based on energy flux components

Abstract. Meltwater from mountainous catchments dominated by snow and ice is a valuable source of fresh water in many regions. At mid-latitudes, seasonal cover glaciers act like natural reservoir storing precipitation during winter releasing it spring summer. Snowmelt usually modelled either energy balance or temperature-index approaches. The approach process-based more sophisticated but requires extensive input data, while the uses degree-day factor (DDF) as key parameter to estimate melt merely air temperature. Despite its simplicity, has proved be powerful tool for simulating process especially large data-scarce catchments. present study attempts quantify effects spatial, temporal, climatic conditions on DDF order gain better understanding which influencing factors are decisive under conditions. analysis based individual flux components; however, formulas estimating presented account situations where observed data limited. A detailed comparison between field-derived estimated values yields fair agreement with bias = 0.14 mm ?C?1 d?1 root mean square error (RMSE) 1.12 d?1. processes controlling snowmelt indicates that cloud albedo clear sky most snow. results this further underline changes season progresses thus also altitude, since melting arrive later at higher elevations. brief influence climate change shows DDFs expected decrease when comparing periods similar degree days, will occur earlier year solar radiation lower, then likely higher. Therefore, cannot treated constant using models forecasting predicting future availability.