Importance of a vertically tilting structure for energizing the North Atlantic Oscillation
Importance of a vertically tilting structure for energizing the North Atlantic Oscillation
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DOI：
10.1038/s41598-020-69551-5
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发表时间：
2020-07
影响因子：
4.6
通讯作者：
P. Martineau;H. Nakamura;Y. Kosaka;A. Yamamoto
中科院分区：
文献类型：
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作者：
P. Martineau;H. Nakamura;Y. Kosaka;A. Yamamoto
北大西洋涛动（英语：North Atlantic Oscillation，NAO）是一种重要的大气变率模式，影响欧洲和美国东北部大部分地区的天气和气候，包括极端事件的发生。北大西洋涛动被认为主要是由迁移性的天气扰动维持的，并且有一个没有垂直倾斜的深层结构。然而，仔细检查发现，相关的异常确实表现出微妙的垂直倾斜，但其动力学含义仍然未知。在这里，我们表明，这种垂直倾斜是至关重要的动力学意义的冬季NAO。我们发现，使用大气再分析数据，倾斜的异常运输热量在明显的热梯度与背景西风急流，平流空气从较冷的北美和格陵兰岛温暖的大西洋，从而加强NAO的热异常。由此产生的转换势能从背景状态是一个更大的能源维持NAO比反馈迁移扰动。因此，我们的研究结果揭示了NAO动力学的基本机制，对改善欧洲-大西洋气候的季节性预测和NAO变率在气候模型中的代表性具有重要意义。
The North Atlantic Oscillation (NAO) is a prominent mode of atmospheric variability that influences weather and climate, including the occurrence of extreme events, over a large part of Europe and Northeastern America. The NAO has been considered to be maintained primarily by migratory weather disturbances and to have a deep structure with no vertical tilt. A careful inspection nonetheless reveals that the associated anomalies do exhibit a subtle vertical tilt, but its dynamical implications are still unknown. Here we show that this vertical tilt is of vital dynamical significance for the wintertime NAO. We find, using atmospheric reanalysis data, that the tilted anomalies transport heat across the pronounced thermal gradient associated with a background westerly jetstream, advecting air from the cooler North America and Greenland to the warmer Atlantic, thereby acting to reinforce NAO’s thermal anomalies. The resultant conversion of potential energy from the background state is a larger energy source for maintaining the NAO than the feedback from migratory disturbances. Our findings thus uncover a fundamental mechanism of the NAO dynamics, with implications for the improvement of seasonal predictions for the Euro-Atlantic climate and the representation of the NAO variability in climate models.