Paleoclimate Constraints on the Spatiotemporal Character of Past and Future Droughts
Paleoclimate Constraints on the Spatiotemporal Character of Past and Future Droughts
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DOI：
10.1175/jcli-d-20-0004.1
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发表时间：
2020-11-15
影响因子：
4.9
通讯作者：
Ault, T. R.
中科院分区：
文献类型：
--
作者：
Coats, S.;Smerdon, J. E.;Ault, T. R.
在三维时空中识别干旱的基于机器学习的方法被应用于气候模式模拟和过去1000年北半球温带水文气候的基于树木年轮的重建，以及21世纪的预测。在此背景下，分析重建和模拟干旱为模拟干旱的时空特征提供了古气候约束。气候模式预测，在未来一个世纪，干旱的持续时间和严重程度将大幅增加，但其空间范围几乎没有变化。然而，气候模式在北半球部分地区持续和严重干旱的时空特征上表现出偏差。我们利用古气候记录和基于线性逆模型的框架得出结论，气候模型低估了未来潜在水文气候状态的范围。然而，当使用不同的水文气候指标进行量化时，持续干旱和严重干旱特征的不同变化使情况更加复杂。总的来说，我们的结果表明，如果我们要增加对未来水文气候预测的信心，就必须更好地理解这些不同的反应和上述偏差。重要的是，本文提出的新框架可以应用于其他气候特征，以稳健地描述其时空特征，并为这些特征的未来变化提供约束。
Machine-learning-based methods that identify drought in three-dimensional space-time are applied to climate model simulations and tree-ring-based reconstructions of hydroclimate over the Northern Hemisphere extratropics for the past 1000 years, as well as twenty-first-century projections. Analyzing reconstructed and simulated drought in this context provides a paleoclimate constraint on the spatiotemporal characteristics of simulated droughts. Climate models project that there will be large increases in the persistence and severity of droughts over the coming century, but with little change in their spatial extent. Nevertheless, climate models exhibit biases in the spatiotemporal characteristics of persistent and severe droughts over parts of the Northern Hemisphere. We use the paleoclimate record and results from a linear inverse modeling-based framework to conclude that climate models underestimate the range of potential future hydroclimate states. Complicating this picture, however, are divergent changes in the characteristics of persistent and severe droughts when quantified using different hydroclimate metrics. Collectively our results imply that these divergent responses and the aforementioned biases must be better understood if we are to increase confidence in future hydroclimate projections. Importantly, the novel framework presented herein can be applied to other climate features to robustly describe their spatiotemporal characteristics and provide constraints on future changes to those characteristics.