Adjustment of regional climate model output for modeling the climatic mass balance of all glaciers on Svalbard.
Adjustment of regional climate model output for modeling the climatic mass balance of all glaciers on Svalbard.
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DOI：
10.1002/2015jd024380
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发表时间：
2016-05-27
期刊：
影响因子：
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通讯作者：
Kohler J
中科院分区：
文献类型：
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作者：
Möller M;Obleitner F;Reijmer CH;Pohjola VA;Głowacki P;Kohler J
冰川物质平衡的大尺度模拟通常依赖于区域气候模式（RCMs）的输出。然而，有限的准确性和空间分辨率的区域协调机制的输出造成的限制，在次区域或地方规模的质量平衡模拟。此外，区域协调机制的产出仍然很少覆盖更大的区域或更长的时期。本研究评估了使用粗分辨率（10 km）RCM输出进行模型强迫的情况下，获得可靠的区域范围冰川质量平衡估计的可能性。我们的数据覆盖了整个斯瓦尔巴群岛超过十年。为了计算质量平衡，我们使用基于指数的模型。模式参数没有校准，但RCM的空气温度和降水场进行了调整，使用现场质量平衡测量作为参考。我们比较了两种不同的校准方法：均方根误差最小化和回归优化。两种方法获得的气温变化（+1.43 ° C vs +2.22 ° C）和降水比例因子（1.23 vs 1.86）差异很大，我们将其归因于参考数据时空分布的不均匀性。我们的模型表明，2000-2011年斯瓦尔巴特群岛的年平均气候质量平衡为-0.05 ± 0.40 m w.e. a-1，平均平衡线海拔为452 ± 200 m。我们发现，有限的空间分辨率的RCM迫使相对于真实的表面形貌和空间均匀的RCM输出调整和质量平衡模型参数的使用是负责大部分的建模不确定性。结果对模型参数不确定性的敏感性非常小，并且不重要。由于现场参考数据的不均匀分布，RCM输出的最佳调整因校准类型而异2000-2011年斯瓦尔巴群岛所有冰川的平均年气候质量平衡为-0.05 m w.e. a-1，平均ELA为452 m asl不准确的RCM地形和不均匀的参考数据分布给模型校准带来了挑战
Large‐scale modeling of glacier mass balance relies often on the output from regional climate models (RCMs). However, the limited accuracy and spatial resolution of RCM output pose limitations on mass balance simulations at subregional or local scales. Moreover, RCM output is still rarely available over larger regions or for longer time periods. This study evaluates the extent to which it is possible to derive reliable region‐wide glacier mass balance estimates, using coarse resolution (10 km) RCM output for model forcing. Our data cover the entire Svalbard archipelago over one decade. To calculate mass balance, we use an index‐based model. Model parameters are not calibrated, but the RCM air temperature and precipitation fields are adjusted using in situ mass balance measurements as reference. We compare two different calibration methods: root mean square error minimization and regression optimization. The obtained air temperature shifts (+1.43°C versus +2.22°C) and precipitation scaling factors (1.23 versus 1.86) differ considerably between the two methods, which we attribute to inhomogeneities in the spatiotemporal distribution of the reference data. Our modeling suggests a mean annual climatic mass balance of −0.05 ± 0.40 m w.e. a−1 for Svalbard over 2000–2011 and a mean equilibrium line altitude of 452 ± 200 m above sea level. We find that the limited spatial resolution of the RCM forcing with respect to real surface topography and the usage of spatially homogeneous RCM output adjustments and mass balance model parameters are responsible for much of the modeling uncertainty. Sensitivity of the results to model parameter uncertainty is comparably small and of minor importance. Optimal adjustment of RCM output varies depending on type of calibration due to inhomogeneous distribution of in situ reference data Mean annual climatic mass balance of all glaciers on Svalbard over 2000–2011 is −0.05 m w.e. a−1 with a mean ELA of 452 m asl Inaccurate RCM topography and inhomogeneous reference data distribution pose challenges to model calibration