关键词: 季节性积雪, 能量平衡, 融雪速率

Abstract: The energy balance approach was used to calculate the snowmelt at a site in the mid-mountain zons of the western Tianshan Mountains. During a 19-day snowmelt period,the study results showed thatnet radiation and sensible heat flux accounted for 75.3% and 22.6% of the incoming energy, while snowmelt and evaporation consumed 95.1% and 4.9% of the energy, respectively.The calculated snowmelt from the energy balance compare favorably with measured ablations,indicating the applicability of energy balance approach to estimate the rate of snowmelt in the mountain environment of the western Tianshan Mounta ins. Weather conditions have great influence on energy flux.During clear days.both net radiation and sensible heat flux increased,resulting in an increase in melt.On overcast days, net radiation became the dominant energy input while flux of sensible and latent heat were small. Windspeed plays a significant role in the exchange of sensible and latant flux between the snow surface and atmosphere. Sizeable transfers of sensible and latant heat occured on warm days with strong wind.Warm air temperature and low windspeed are primary characteristics of weather conditions in the westren Tianshan Mountains during the snow-melt season.Because of this,vapour pressure of the air often rises close to or above the saturation vapour pressure for melting snow. Therefore, under warm and low windspeed conditions, the large temperature gradient and reduced vapour gradient above the snow led to a great transfer of sensible flux and a minor latent flux,and this is why the importance of sensible heat was far more significant than that of latent heat in the energy halance.

Key words: Seasonal snow, Energy balance, Rate of snowmelt