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Assessment of current methods of positive degree-day calculation using in situ observations from glaciated regions

机译:利用冰原地区的原位观测资料评估目前的正度日计算方法

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摘要

The continued use of the Positive Degree-Day (PDD) method to predict ice sheet melt is generally favoured over surface energy balance methods partly due to the computational efficiency of the algorithm and the requirement of only one input variable (temperature). In this paper we revisit some of the assumptions governing the application of the PDD method. Using hourly temperature data from the GC-Net network we test the assumption that monthly PDD total (PDDm) can be represented by a Gaussian distribution with fixed standard deviation of monthly temperature (σM). The results presented here show that the common assumption of fixed σM does not hold, and that σM may be represented more accurately as a quadratic function of average monthly temperature. For Greenland, the mean absolute error in predicting PDDm using our methodology is 3.9°C*day, representing a significant improvement on current methods (7.8°C*day, when σM = 4.5°C). Over a range of glaciated settings, our method reproduces PDDm, on average, to within 1.5 - 8.5°C*day, compared to 4.4 - 15.7°C*day when σM = 4.5°. The improvement arises because we capture the systematic reduction in temperature variance that is observed over melting snow and ice, when surface temperatures cannot warm above O°C.
机译:继续使用正度日(PDD)方法来预测冰盖融化通常优于表面能平衡方法,部分原因是该算法的计算效率高,并且只需要一个输入变量(温度)。在本文中,我们将回顾一些支配PDD方法应用的假设。使用来自GC-Net网络的每小时温度数据,我们测试了以下假设:每月PDD总量(PDDm)可以由固定的每月温度标准偏差(σM)的高斯分布表示。此处给出的结果表明,固定的σM的一般假设不成立,并且σM可以更准确地表示为平均月温度的二次函数。对于格陵兰岛,使用我们的方法预测PDDm的平均绝对误差为3.9°C *天,这表示当前方法(7.8°C *天,σM= 4.5°C时)有显着改善。在一系列冰河环境中,我们的方法平均将PDDm复制到1.5-8.5°C *天,而σM= 4.5°时则为4.4-15.7°C *天。之所以出现这种改进,是因为当表面温度不能升至O°C以上时,我们捕获了融化的雪和冰时观察到的温度变化的系统减小。

著录项

  • 作者

    Wake, Leanne; Marshall, Shawn;

  • 作者单位
  • 年度 2015
  • 总页数
  • 原文格式 PDF
  • 正文语种 {"code":"en","name":"English","id":9}
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