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Increased shear in the North Atlantic upper-level jet stream over the past four decades

机译：在过去的四十年里，在北大西洋上层喷射流中增加了剪切

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Earth's equator-to-pole temperature gradient drives westerly mid-latitude jet streams through thermal wind balance(1). In the upper atmosphere, anthropogenic climate change is strengthening this meridional temperature gradient by cooling the polar lower stratosphere(2,3) and warming the tropical upper troposphere(4-6), acting to strengthen the upper-level jet stream(7). In contrast, in the lower atmosphere, Arctic amplification of global warming is weakening the meridional temperature gradient(8-10), acting to weaken the upper-level jet stream. Therefore, trends in the speed of the upper-level jet stream(11-13) represent a closely balanced tugof-war between two competing effects at different altitudes(14). It is possible to isolate one of the competing effects by analysing the vertical shear-the change in wind speed with height-instead of the wind speed, but this approach has not previously been taken. Here we show that, although the zonal wind speed in the North Atlantic polar jet stream at 250 hectopascals has not changed since the start of the observational satellite era in 1979, the vertical shear has increased by 15 per cent (with a range of 11-17 per cent) according to three different reanalysis datasets(15-17) . We further show that this trend is attributable to the thermal wind response to the enhanced upper-level meridional temperature gradient. Our results indicate that climate change may be having a larger impact on the North Atlantic jet stream than previously thought. The increased vertical shear is consistent with the intensification of shear-driven clear-air turbulence expected from climate change(18-20), which will affect aviation in the busy transatlantic flight corridor by creating a more turbulent flying environment for aircraft. We conclude that the effects of climate change and variability on the upper-level jet stream are being partly obscured by the traditional focus on wind speed rather than wind shear.
机译：地球赤道到极温度梯度通过热风平衡（1）驱动西方中纬度喷射流。在上层大气中，人体气候变化通过冷却极性下划线（2,3）并加热热带上层（4-6）来加强该赞聚温度梯度，作用以加强上层喷射流（7）。相比之下，在较低的大气中，全球变暖的北极放大是削弱了子午温度梯度（8-10），作用以削弱上层射流。因此，上层射流流（11-13）的速度的趋势代表了在不同高度（14）的两个竞争效果之间的紧密平衡的Tugof-战争。可以通过分析垂直剪切 - 使用高度 - 而不是风速来分析垂直剪切的变化来隔离其中一个竞争效果，但先前尚未采用这种方法。在这里，我们展示了，尽管自1979年观察卫星时代的开始以来，北大西洋射流在250张泮帕帕氏犬的地区速度没有改变，但垂直剪切增加了15％（范围为11-根据三种不同的再分析数据集（15-17），17％）。我们进一步表明，这种趋势是归因于热风响应增强的高级子午温度梯度。我们的结果表明，气候变化可能对北大西洋喷射流影响比以前的思想更大。增加的垂直剪切与影响气候变化（18-20）预期的剪切驱动的透明空气湍流的强化一致，这将通过为飞机产生更大的湍流飞行环境来影响繁忙的跨大气飞行走廊的航空。我们得出结论，气候变化和可变性对上层喷射流的影响是由传统的重点在风速上而不是风剪的影响。

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  • 来源
    《Nature》 |2019年第7771期|639-642|共4页
  • 作者

    Lee Simon H.; Williams Paul D.; Frame Thomas H. A.;

  • 作者单位

    Univ Reading Dept Meteorol Reading Berks England;

    Univ Reading Dept Meteorol Reading Berks England;

    Univ Reading Dept Meteorol Reading Berks England;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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