天山季节性积雪的能量平衡研究和融雪速率模拟

ENERGY BAIANCE AND SNOWMELT SIMULATION OF SEASONAL SNOW IN THE WESTERN TIANSHAN MOUNTAINS,CHINA

本文采用能量平衡法模拟计算中国西部天山山地季节性积雪的融雪速率。结果表明:在融雪期,净辐射和感热通量分别占融雪能量输入的75.3％和22.6％;用于融雪和雪面蒸发所消耗的能量分别占吸收能量的95.1％和4.9％。用能量平衡法所计算的融雪速率和实测的雪面数据吻合的较好,表明用能量平衡法估算天山山地季节性积雪的融雪速率是可行的。

The energy balance approach was used to calculate the snowmelt at a site in the mid-mountain zons of the western Tianshan Mounta ins. 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, respect ively.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,result ing 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 melt ing sno w. Therefore, under warm and low windspeed condit ions, 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.