A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard
A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard
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DOI：
10.5194/tc-6-1049-2012
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发表时间：
2012-01-01
期刊：
影响因子：
5.2
通讯作者：
Moeller, M.
中科院分区：
文献类型：
--
作者：
Moeller, M.
维斯特纳冰帽位于斯瓦尔巴群岛东北部，是欧亚北极地区最大的冰体之一。它的表面反照率在理解和模拟它的能量和质量平衡方面起着关键作用。反照率演变的主要控制因素，即降水和气温以及积雪深度和融化持续时间，几乎完全随整个冰盖的地形高度而变化。因此，地表反照率可以预期形成一个可比的模式。本文提出了一种新的统计模型，该模型基于月分辨率的最小气象变量集来估计冰盖的平均高度反照率剖面。模式计算基于人工量雨雪比的s型函数和累积降雪量和累积正日数的线性函数。MODIS雪产品MOD10A1 2001-2008年3 - 10月的地表反照率场可作为模型定标和交叉验证的基础。气象模式输入时间为2000年9月至2008年10月，基于靠近冰盖的栅格点的ERA-Interim数据，反照率模式表现出较好的性能。观测值与模拟反照率在垂直剖面上的均方根误差为0.057 +/- 0.028（平均+/-一个标准差）。面积加权平均值甚至降至0.054。明显较高的偏差（0.07-0.09）只出现在冰盖的最底部和最顶部，这些部分面积较小或几乎不受表面融化的影响。因此，本研究提出的新的最小统计反照率模型可以高精度地再现Vestfonna冰帽的反照率演变，因此完全适合进一步应用于更广泛的冰帽能量或质量平衡研究。
The ice cap Vestfonna is located in northeastern Svalbard and forms one of the largest ice bodies of the Eurasian Arctic. Its surface albedo plays a key role in the understanding and modelling of its energy and mass balance. The principle governing factors for albedo evolution, i.e. precipitation and air temperature and therewith snow depth and melt duration, were found to vary almost exclusively with terrain elevation throughout the ice cap. Hence, surface albedo can be expected to develop a comparable pattern. A new statistical model is presented that estimates this mean altitudinal albedo profile of the ice cap on the basis of a minimal set of meteorological variables on a monthly resolution. Model calculations are based on a sigmoid function of the artificial quantity rain-snow ratio and a linear function of cumulative snowfall and cumulative positive degree days. Surface albedo fields of the MODIS snow product MOD10A1 from the period March to October in the years 2001-2008 serve as a basis for both calibration and cross-validation of the model. The meteorological model input covers the period September 2000 until October 2008 and is based on ERA-Interim data of a grid point located close to the ice cap. The albedo model shows a good performance. The root mean square error between observed and modelled albedo values along the altitudinal profile is 0.057 +/- 0.028 (mean +/- one standard deviation). The area weighted mean even reduces to a value of 0.054. Distinctly higher deviations (0.07-0.09) are only present throughout the very lowest and uppermost parts of the ice cap that are either small in area or hardly affected by surface melt. Thus, the new, minimal, statistical albedo model presented in this study is found to reproduce the albedo evolution on Vestfonna ice cap on a high level of accuracy and is thus suggested to be fully suitable for further application in broader energy or mass-balance studies of the ice cap.