Supraglacial debris is significant in many regions and complicates modeling of glacier melt, which is required for predicting glacier change and its influences on hydrology and sea-level rise. Temperature-index models are a popular alternative to energy-balance models when forcing data are limited, but their transferability among glaciers and inherent uncertainty have not been documented in application to debris-covered glaciers. Here, melt factors were compiled directly from published studies or computed from reported melt and MERRA-2 air temperature for 27 debris-covered glaciers around the world. Linear mixed-effects models were fit to predict melt factors from debris thickness and variables including debris lithology and MERRA-2 radiative exchange. The models were tested by leave-one-site-out cross-validation based on predicted melt rates. The best model included debris thickness (fixed effect) and glacier and year (random effects). Predictions were more accurate using MERRA-2 than on-site air temperature data, and pooling MERRA-2-derived and reported melt factors improved cross-validation accuracy more than including additional predictors such as shortwave or longwave radiation. At one glacier where monthly ablation was measured over 4 years, seasonal variation of melt factors suggested that heat storage significantly affected the relation between melt and energy exchange at the debris surface.

中文翻译：

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评估碎片覆盖的冰川融化经验模型的可转移性

冰上碎片在许多地区都很重要，并且使冰川融化的建模复杂化，这对于预测冰川变化及其对水文和海平面上升的影响是必需的。当强迫数据有限时，温度指数模型是能量平衡模型的一种流行替代方案，但它们在冰川之间的可转移性和固有的不确定性在应用于碎片覆盖的冰川时尚未得到证明。在这里，融化因子直接来自已发表的研究，或根据报告的融化和 MERRA-2 气温计算出全球 27 个被碎片覆盖的冰川。线性混合效应模型适用于预测来自碎屑厚度和变量的熔体因子，包括碎屑岩性和 MERRA-2 辐射交换。这些模型通过基于预测的熔体速率的留有交叉验证进行测试。最佳模型包括碎片厚度（固定效应）和冰川和年份（随机效应）。使用 MERRA-2 的预测比现场气温数据更准确，合并 MERRA-2 衍生和报告的融化因子比包括短波或长波辐射等其他预测因子更能提高交叉验证的准确性。在一个冰川上测量了 4 年的每月消融，融化因素的季节性变化表明蓄热显着影响了融化和碎片表面能量交换之间的关系。合并 MERRA-2 衍生和报告的融化因子比包括其他预测因子（如短波或长波辐射）更能提高交叉验证的准确性。在一个冰川上测量了 4 年的每月消融，融化因素的季节性变化表明蓄热显着影响了融化和碎片表面能量交换之间的关系。合并 MERRA-2 衍生和报告的融化因子比包括其他预测因子（如短波或长波辐射）更能提高交叉验证的准确性。在一个冰川上测量了 4 年的每月消融，融化因素的季节性变化表明蓄热显着影响了融化和碎片表面能量交换之间的关系。