Polar Lows
Polar Lows
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DOI：
10.1093/acrefore/9780190228620.013.775
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发表时间：
2020-06
期刊：
影响因子：
--
通讯作者：
A. Terpstra;Shun-ichi Watanabe
中科院分区：
文献类型：
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作者：
A. Terpstra;Shun-ichi Watanabe
极地低压是在主极锋两极方向的两个半球发展的强烈的海洋中尺度气旋。这些快速发展的强风暴伴随着强风、强降水（冰雹和雪）和汹涌的海况。极地低压会扰乱极地海洋区域的人类活动，如旅游、渔业、运输、研究活动和自然资源勘探，从而产生重大的社会经济影响。登陆后，它们迅速腐烂，但其狂风和大量降雪影响了沿海地区的当地社区，导致机场关闭，交通中断和雪崩风险增加。极地低压主要是一种冬季现象，往往是在极地空气团从冰层覆盖的地区经过邻近的开阔海洋时形成的。这些所谓的冷空气爆发是由天气尺度的大气结构驱动的，极地低压通常沿着与这些冷空气爆发相关的气团边界发展。局部地形特征和海冰结构也在极地低压发展的环境预处理中起着重要作用。极地低压发展的动力学路径包括湿斜压不稳定、对称对流不稳定和锋面不稳定，但由于观测稀疏和再分析资料分辨率不足，对这些机制的验证是有限的。频繁出现极地低压的海域是全球海洋环流的重要气候区域，因此这些地区大气和海洋之间能量交换的局部变化可能会影响全球气候系统。最近的研究表明，中尺度气旋加强了热量和动量交换，通过触发海洋中深水的形成和改变大气中的水平混合，可能对海洋热量输送产生显著影响。自卫星时代开始以来，北方半球海冰覆盖的稳步下降扩大了无冰极地地区，从而扩大了极地低压发展的地区，但根据未来气候情景，极地低压的数量预计将减少。
Polar lows are intense maritime mesoscale cyclones developing in both hemispheres poleward of the main polar front. These rapidly developing severe storms are accompanied by strong winds, heavy precipitation (hail and snow), and rough sea states. Polar lows can have significant socio-economic impact by disrupting human activities in the maritime polar regions, such as tourism, fisheries, transportation, research activities, and exploration of natural resources. Upon landfall, they quickly decay, but their blustery winds and substantial snowfall affect the local communities in coastal regions, resulting in airport-closure, transportation breakdown and increased avalanche risk. Polar lows are primarily a winter phenomenon and tend to develop during excursions of polar air masses, originating from ice-covered areas, over the adjacent open ocean. These so-called cold-air outbreaks are driven by the synoptic scale atmospheric configuration, and polar lows usually develop along air-mass boundaries associated with these cold-air outbreaks. Local orographic features and the sea-ice configuration also play prominent roles in pre-conditioning the environment for polar low development. Proposed dynamical pathways for polar low development include moist baroclinic instability, symmetric convective instability, and frontal instability, but verification of these mechanisms is limited due to sparse observations and insufficient resolution of reanalysis data. Maritime areas with a frequent polar low presence are climatologically important regions for the global ocean circulation, hence local changes in energy exchange between the atmosphere and ocean in these regions potentially impacts the global climate system. Recent research indicates that the enhanced heat and momentum exchange by mesoscale cyclones likely has a pronounced impact on ocean heat transport by triggering deep water formation in the ocean and by modifying horizontal mixing in the atmosphere. Since the beginning of the satellite-era a steady decline of sea-ice cover in the Northern Hemisphere has expanded the ice-free polar regions, and thus the areas for polar low development, yet the number of polar lows is projected to decline under future climate scenarios.