Funding information Strategic Environmental Research and Development Program (SERDP), Grant/ Award Number: RC18-1658 Abstract Blocked atmospheric flows over Greenland and the North Atlantic Arctic (NAA) can be defined by the appearance of an anomalous ridge, many times off the western margin of continents, that deflects traveling cyclones from their usual storm tracks. Atmospheric blocking often produces a strong equatorward deflection of polar air on the eastern flank of the anticyclone, including severe cold episodes in winter, and severe droughts and heat waves in summer. Recent changes in low-frequency atmospheric circulation in the NAA have increased sensible heat and moisture advection from the mid-latitudes into this region. In this study, we explore the frequency and seasonality of extreme Greenland blocking, and we explore the relationship between extreme blocking and moisture transport into and over the region. We quantify atmospheric flow blocking over Greenland using the Greenland Blocking Index, and extreme blocking is defined from 1980 to 2019 at the 90th, 95th, 97th, and 99th percentiles for both summer (June to August) and winter (December to February) seasons. Moisture transport over Greenland was defined by calculating daily integrated vapor transport from the ERA-Interim reanalysis over the region from 15! to 85!W and 55! to 80!N. The frequency of extreme blocking over Greenland was found to have increased in the most recent two decades (2000–2019) compared to the period 1980–1999. In addition, the probability of above-average moisture transport occurring on a day with extreme blocking is high in both summer and winter, with the highest probability of high moisture transport during an extreme Greenland Blocking Index day in winter. These findings are unique to this work and suggest future work on the role of moisture transport in developing or sustaining blocks over Greenland.

中文翻译：

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极端格陵兰阻塞和高纬度水分输送

资金信息 战略环境研究与发展计划 (SERDP)，拨款/奖励编号：RC18-1658 摘要 格陵兰岛和北大西洋北极 (NAA) 上空的大气流动受阻可以通过异常山脊的出现来定义，该异常山脊多次远离西部大陆边缘，使行进的气旋偏离它们通常的风暴轨迹。大气阻塞常常使反气旋东翼的极地空气发生强烈的赤道偏转，包括冬季的严寒天气和夏季的严重干旱和热浪。最近 NAA 中低频大气环流的变化增加了从中纬度到该地区的感热和湿气平流。在这项研究中，我们探讨了格陵兰岛极端阻塞的频率和季节性，我们探索了极端阻塞和水分输送到该地区和越过该地区的关系。我们使用格陵兰阻塞指数来量化格陵兰上空的大气流动阻塞，极端阻塞定义为 1980 年至 2019 年夏季（6 月至 8 月）和冬季（12 月至 2 月）季节的第 90、95、97 和 99 分位数。格陵兰上空的水分输送是通过计算来自 ERA-Interim 再分析的每日综合蒸汽输送来定义的，该地区从 15! 到 85！W 和 55！到 80!N。与 1980 年至 1999 年期间相比，最近二十年（2000 年至 2019 年）格陵兰上空极端阻塞的频率有所增加。此外，在夏季和冬季，极端阻塞的一天发生高于平均水平的水分输送的概率很高，在格陵兰岛冬季极端阻塞指数日期间高水分传输的可能性最高。这些发现对这项工作来说是独一无二的，并为未来关于水分输送在格陵兰岛开发或维持区块中的作用的工作提出了建议。