How do intermittency and simultaneous processes obfuscate the Arctic influence on midlatitude winter extreme weather events?
How do intermittency and simultaneous processes obfuscate the Arctic influence on midlatitude winter extreme weather events?
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DOI：
10.1088/1748-9326/abdb5d
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发表时间：
2021-01
影响因子：
6.7
通讯作者：
J. Overland;T. Ballinger;J. Cohen;J. Francis;E. Hanna;Ralf Jaiser;Baek‐Min Kim;Seong‐Joong Kim
中科院分区：
文献类型：
--
作者：
J. Overland;T. Ballinger;J. Cohen;J. Francis;E. Hanna;Ralf Jaiser;Baek‐Min Kim;Seong‐Joong Kim
北极环境的显着变化为影响数十亿人的中纬度地区异常天气模式增加了新的潜在驱动因素。然而，最近对这些北极/中纬度天气联系的研究得出了不一致的结论。不确定性的一个来源是大气的混乱性质。北极快速变暖的热动力强迫通过改变地表热通量和大范围的温度和压力梯度而导致天气事件。但大气动力学的内部变化——急流、阻塞和平流层极涡（SPV）的位置、强度和特征的变化——掩盖了直接原因和影响。了解这些相关过程对于区分北极强迫变化和自然变化非常重要。例如，在初冬，巴伦支海/喀拉海海冰覆盖范围的减少可能会加强北大西洋/北极与中亚之间现有的大气遥相关，并影响东亚下游的天气。楚科奇海海冰减少会放大阿拉斯加附近高压的大气脊，影响整个北美下游的天气。冬末，SPV 向南移动，加上对流层，导致欧亚大陆和北美出现极端天气。热带和海冰条件的结合可以调节 SPV 的变化。关于北极/中纬度天气联系的观测证据不断积累，以及对与先前存在的气候状态的联系的了解。相对于自然大气变化，海冰损失本身在北极/中纬度天气联系中发挥着次要作用；北极放大的全面影响仍不确定。
Pronounced changes in the Arctic environment add a new potential driver of anomalous weather patterns in midlatitudes that affect billions of people. Recent studies of these Arctic/midlatitude weather linkages, however, state inconsistent conclusions. A source of uncertainty arises from the chaotic nature of the atmosphere. Thermodynamic forcing by a rapidly warming Arctic contributes to weather events through changing surface heat fluxes and large-scale temperature and pressure gradients. But internal shifts in atmospheric dynamics—the variability of the location, strength, and character of the jet stream, blocking, and stratospheric polar vortex (SPV)—obscure the direct causes and effects. It is important to understand these associated processes to differentiate Arctic-forced variability from natural variability. For example in early winter, reduced Barents/Kara Seas sea-ice coverage may reinforce existing atmospheric teleconnections between the North Atlantic/Arctic and central Asia, and affect downstream weather in East Asia. Reduced sea ice in the Chukchi Sea can amplify atmospheric ridging of high pressure near Alaska, influencing downstream weather across North America. In late winter southward displacement of the SPV, coupled to the troposphere, leads to weather extremes in Eurasia and North America. Combined tropical and sea ice conditions can modulate the variability of the SPV. Observational evidence for Arctic/midlatitude weather linkages continues to accumulate, along with understanding of connections with pre-existing climate states. Relative to natural atmospheric variability, sea-ice loss alone has played a secondary role in Arctic/midlatitude weather linkages; the full influence of Arctic amplification remains uncertain.