Degree-day model,based on a linear relationship between glacier/snow ablation and positive accumulated temperature,is widely used for estimating glacier and snow melt for its simplicity and outstanding performance.However,degree-day factor (DDF),as the most important parameter in this model,is difficult to obtain in an extensive region,especially in Yarlung Zangbo River Basin,which is the highest basin in the world and characterized by rugged and complex terrain.With the development of distributed hydrological model,increasing demand for spatial dataset of DDFs has become a challenging issue in the relevant fields.The objective of this study is to develop an algorithm to spatially estimate the positive DDFs based on available observed DDFs.Topographical factors are fully taken into account to correlate with DDFs,and spatial DDFs in moderate resolution are generated by stepwise and neighboring mean filtering improved in this study.Finally,the produced DDFs are indirectly validated by snow lines in different orientations,and the correlation coefficient of up to 0.82 proves that the DDFs generated in the present study are reasonable in applications.The spatial distribution of DDFs in Yarlung Zangbo River Basin shows that DDFs in downstream were lower than those in upstream and midstream,which is probably because there is less precipitation and more solar radiation in upstream and midstream than in downstream,due to monsoon from India Ocean.To better estimate glacial meltwater runoff and manage water resources in Yarlung Zangbo River Basin,further studies on spatial variability in DDFs are yet needed.%度日模型以冰川/积雪消融与正积温的线性关系为基础,因其简单易用且性能卓越而被广泛应用于冰川与积雪径流研究.然而,度日因子,作为模型中最重要的参数,很难获取空间分布数据,尤其在海拔较高和地形极其复杂的雅鲁藏布江流域.随着分布式水文模型的发展,对度日因子的空间分布数据的需求已成为研究冰川消融领域的挑战性问题.本研究的目标是基于实际观测的冰川度日因子估算雅鲁藏布江流域内分布式度日因子数据.其中,在雅鲁藏布江流域内或周围已观测冰川的地形因子与度日因子高度相关性被充分考虑.最后,利用不同冰川朝向的雪线进行间接验证本研究得到的分布式度日因子.本工作表明,基于实际观测的度日因子,采用充分考虑地形因素的回归模型及改进的滤波算法可以很好地重建雅鲁藏布江流域空间分布的度日因子数据.结果表明,雅鲁藏布江流域下游的冰川度日因子比上游和中游低,可能是由于上游和中游受印度洋季风影响导致降雨较少以及太阳辐射较多.为了能更好地估算冰川融水径流和管理水资源,分布式的冰川度日因子重建及验证仍需进一步研究.
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