Gap‐Filling Algorithm for Ground Surface Temperature Data Measured in Permafrost and Periglacial Environments
Gap‐Filling Algorithm for Ground Surface Temperature Data Measured in Permafrost and Periglacial Environments
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DOI：
10.1002/ppp.1913
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发表时间：
2017
影响因子：
5
通讯作者：
B. Staub;A. Hasler;J. Noetzli;R. Delaloye
中科院分区：
文献类型：
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作者：
B. Staub;A. Hasler;J. Noetzli;R. Delaloye
山地多年冻土区地表温度（GST）是一个广泛应用的测量数据，但其时间序列数据可能会因间断而中断。差距使分析伐木者和地点之间的时间和空间变异性所需的总量和指数的计算复杂化。我们提出了一个算法来估计每日平均GST和由此产生的不确定性。该算法的目的是自动填补数据库中的几十到几百个时间序列，例如，瑞士永久冻土监测网络（PERMOS）的数据缺口。使用大量随机生成的人工间隙，我们验证了差距填充程序在以下方面的性能：（1）年平均值产生的偏倚，（2）解冻和冻结度日数，以及（3）不确定性估计的准确度。虽然分位数映射总体上提供了最可靠的间隙填充方法，但相邻值之间的线性插值对于长达3-5天的间隙持续时间同样表现良好。找到最相似的回归量是至关重要的，也是误差的主要来源，特别是因为高山地形中地面和积雪特性的空间和时间变异性很大。将差距填补技术应用于PERMOS GST数据，可用于分析的完整水文年总数增加了70%（>450填补缺口），可能不会超过计算的年平均值± 0.25 °C的最大不确定性。版权所有© 2016约翰威利父子有限公司.
Ground surface temperatures (GST) are widely measured in mountain permafrost areas, but their time series data can be interrupted by gaps. Gaps complicate the calculation of aggregates and indices required for analysing temporal and spatial variability between loggers and sites. We present an algorithm to estimate daily mean GST and the resulting uncertainty. The algorithm is designed to automatically fill data gaps in a database of several tens to hundreds of time series, for example, the Swiss Permafrost Monitoring Network (PERMOS). Using numerous randomly generated artificial gaps, we validated the performance of the gap‐filling routine in terms of (1) the bias resulting on annual means, (2) thawing and freezing degree‐days, and (3) the accuracy of the uncertainty estimation. Although quantile mapping provided the most reliable gap‐filling approach overall, linear interpolation between neighbouring values performed equally well for gap durations of up to 3–5 days. Finding the most similar regressors is crucial and also the main source of errors, particularly because of the large spatial and temporal variability of ground and snow properties in high‐mountain terrains. Applying the gap‐filling technique to the PERMOS GST data increased the total number of complete hydrological years available for analysis by 70 per cent (>450‐filled gaps), likely without exceeding a maximal uncertainty of ± 0.25 °C in calculated annual mean values. Copyright © 2016 John Wiley & Sons, Ltd.