Drought is among the costliest natural disasters and its spatiotemporal scales are larger than those of other water-related disasters. However, our understanding of drought causative mechanisms is less than complete, inhibiting accurate drought forecasting and early warning. While sea surface temperature teleconnection governs the 10%–60% precipitation variability at intra-seasonal to multiannual scales, some of the unexplained variability can be understood by internal atmospheric variability, represented by Rossby wave packets (RWPs), and implications of atmospheric rivers (ARs). The amplitude and phase speed of the recurrent RWPs (RRWPs) and the atmospheric river index developed in this study were used to analyze the impacts of RWPs and ARs on droughts detected by three-dimensional drought clustering algorithms for the continental U.S. during 1951–2015. The occurrence of RRWPs raised the likelihood of the occurrence of more severe drought than did the non-occurrence of RRWPs. The increase in the occurrence of RRWPs with low phase speed escalated drought severity, area, and duration. Furthermore, the drying ARs affected drought by increasing the severity and area of extreme droughts. We measured the level of contributions of RRWPs and ARs to extreme drought occurrences. The drying ARs contributed more to extreme droughts than did RRWPs. However, the co-occurrence of ARs and RRWPs contributed more than did each individually. Our findings of the implications of RRWPs and ARs on drought characteristics offer the potential to improve our understanding of drought causative mechanisms that can enhance the proactive drought mitigation measures.

中文翻译：

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罗斯比波包和大气河流对美国大陆气象干旱的影响

干旱是损失最惨重的自然灾害之一，其时空尺度大于其他与水有关的灾害。然而，我们对干旱成因机制的了解并不完整，阻碍了准确的干旱预报和预警。虽然海面温度遥相关控制了季节内到多年尺度的 10%–60% 降水变异，但一些无法解释的变异可以通过内部大气变异来理解，以罗斯比波包 (RWP) 为代表，以及大气河流的影响（ AR)。本研究开发的循环 RWPs (RRWPs) 和大气河流指数的幅度和相位速度用于分析 RWPs 和 ARs 对美国大陆三维干旱聚类算法检测到的干旱的影响 1951-2015 年期间。RRWP 的发生比 RRWP 的未发生增加了发生更严重干旱的可能性。低相速度的 RRWP 发生的增加使干旱的严重程度、面积和持续时间升级。此外，干旱 AR 通过增加极端干旱的严重程度和面积来影响干旱。我们测量了 RRWP 和 AR 对极端干旱事件的贡献水平。干燥的 ARs 比 RRWPs 对极端干旱的贡献更大。然而，ARs 和 RRWPs 的共同发生比各自的贡献更大。我们关于 RRWPs 和 ARs 对干旱特征影响的发现为提高我们对干旱成因机制的理解提供了可能，这些机制可以增强积极的干旱缓解措施。RRWP 的发生比 RRWP 的未发生增加了发生更严重干旱的可能性。低相速度的 RRWP 发生的增加使干旱的严重程度、面积和持续时间升级。此外，干旱 AR 通过增加极端干旱的严重程度和面积来影响干旱。我们测量了 RRWP 和 AR 对极端干旱事件的贡献水平。干燥的 ARs 比 RRWPs 对极端干旱的贡献更大。然而，ARs 和 RRWPs 的共同发生比各自的贡献更大。我们关于 RRWPs 和 ARs 对干旱特征影响的发现为提高我们对干旱成因机制的理解提供了可能，这些机制可以增强积极的干旱缓解措施。RRWP 的发生比 RRWP 的未发生增加了发生更严重干旱的可能性。低相速度的 RRWP 发生的增加使干旱的严重程度、面积和持续时间升级。此外，干旱 AR 通过增加极端干旱的严重程度和面积来影响干旱。我们测量了 RRWP 和 AR 对极端干旱事件的贡献水平。干燥的 ARs 比 RRWPs 对极端干旱的贡献更大。然而，ARs 和 RRWPs 的共同发生比各自的贡献更大。我们关于 RRWPs 和 ARs 对干旱特征影响的发现为提高我们对干旱成因机制的理解提供了可能，这些机制可以增强积极的干旱缓解措施。