Energy Balance Melt Research Articles

Hydrological response of two high altitude Swiss catchments to energy balance and temperature index melt schemes

Comparison of energy Balance (EB) and temperature Index (TI) snow/ice melt methods for glacio-hydrological modeling in the Alps has been the subject of numerous studies; however, the debate on which method is preferable under which conditions and for which application is still ongoing. In this study, both melting routines were tested within the complex numerical framework of the fully distributed model (Alpine3D) to analyze the differences. We included two high-altitude Swiss alpine glaciered catchments, which represent two distinct types of glaciers, namely cirque and valley glaciers, with different weather conditions, topography, and data type. In this experiment, hydrological discharge in the Damma catchment was overestimated by the model with EB approach, which demonstrated Nash-Sutcliffe efficiency (NSE) of 0.61 mainly due to the overestimation of wind speed and longwave radiation. On the other hand, model with TI approach obtained a high NSE of 0.93, as this simple conceptual model does not rely on the abovementioned variables. For the Arolla catchment, better results were observed for both EB and TI melt schemes, with slight underestimation in modeled runoff as shown by NSEs of 0.89 and 0.77, respectively. The very satisfactory performance of EB model at the Arolla catchment is due to the use of input data sets from local weather stations that are more representative of the real catchment conditions. It was observed that the EB melt model performs better if driven with correct meteorological data sets from catchment-representative stations and that the calibration procedure of TI-melt model significantly affects its accuracy.

An analysis of short‐term albedo variations at haut glacier d'arolla, switzerland

An analysis of ten‐minute albedo variations, recorded on Haut Glacier d'Arolla, Switzerland, over an 11 day period in the 1999 ablation season is presented. Most of the short‐term (<1 day) albedo variability is caused by variations in cloud cover, while solar zenith angle variations in the range 25° to 75° are of minor importance, probably due to the predominantly cloudy conditions during the measurement period. A new method to calculate albedo variation as a function of cloud cover is developed. Short‐term albedo variations are expressed by the ratio of the measured albedo to the daily albedo ‘minimum’, defined as the albedo under cloud‐free conditions when the solar zenith angle is <50°. Variations in cloud cover are quantified by the ratio of the measured incoming shortwave radiation flux to the theoretical direct‐beam shortwave radiation flux. The resulting relationships are successful, explaining 83% and 87–90% of short‐term albedo variation on snow and ice respectively, and may be incorporated into albedo parameterizations already used in numerical energy balance melt models, without the need for additional data. Simulations with a glacier energy balance model suggest that melt rates are overestimated by between 1 and 3 mm water equivalent per day if a correction is not made for the increase in albedo under cloudy conditions. Other causes of albedo variation are identified and evidence is found for the removal of fine debris from the glacier surface by intense rainfall, leading to an albedo increase. The implications for energy balance models and satellite‐derived albedo measurements are discussed.