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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming
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Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming

机译：低云压抑了北极的空气形成并加剧了高纬度大陆冬季的变暖

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High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback—consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state—slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the “lapse rate feedback” in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.
机译：近几十年来，高纬度大陆的升温速度比全球其他地区要快得多，尤其是在冬季，冬季保持大陆内部温暖，无霜的状况一直是过去气候适宜的长期问题。我们在各种条件下使用理想化的单列大气模型来研究空气质量从极高纬度的海洋空气（具有指定的初始温度曲线）转变为冷得多的高纬度大陆空气的极夜过程。我们发现，低云反馈（包括随着初始状态的变暖而光学厚的液态云持续时间的强劲增长）减慢了表面的辐射冷却并放大了大陆变暖。这种低云反馈使海洋表面的初始地面温度每升高1度，大陆表面的温度大约增加2度，从而有效地抑制了北极的空气形成。对于初始海洋温度为20°C，地表空气温度降至冰点以下所花费的时间非线性地增加到〜10 d。这些结果，再加上耦合模型比较项目的第5阶段气候模型运行分析得到补充，表明在较温暖的气候中云水路径和地表云长波强迫大大增加，这表明人为气候变化模拟中的“流失率反馈”可能是与低云对低层对流层分层的影响有关。结果还表明，光学上较厚的层云层可以在适当的气候下帮助维持冬季无霜的内陆。

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