On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016
On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016
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DOI：
10.5194/acp-18-4803-2018
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发表时间：
2017-11
影响因子：
6.3
通讯作者：
V. Matthias;M. Ern
中科院分区：
文献类型：
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作者：
V. Matthias;M. Ern
抽象的。 2015/2016年仲冬的特点是副热带中层异常强烈的极夜急流（PNJ）和异常大的静止行星波（SPW）振幅。因此，本研究的目的是寻找 2015/2016 年仲冬研究期间这些中层超表面波的起源。研究时间分为两个阶段：第一阶段从2015年12月下旬至2016年1月上旬（第一阶段），第二阶段从1月初至2016年1月中旬（第二阶段）。虽然在 I 期副热带中间层中 SPW 1 占主导地位，但在 II 期却是 SPW 2 占主导地位。有三种可能性解释SPW如何在中间层中发生：（1）它们从平流层向上传播，（2）它们是由纵向可变重力波（GW）阻力原位产生的，或者（3）它们是由正压和/或斜压不稳定性原位产生的。利用微波临边探测器 (MLS) 的全球卫星观测和使用宽带发射辐射测量 (SABER) 的大气探测，对这两个时期的中层 SPW 的起源进行了研究。我们发现，由于强烈的PNJ，SPW无法向上传播到50∘N以北的中间层，而是向上和赤道偏转进入副热带中间层。我们表明，在副热带中间层观测到的 SPW 与中纬度平流层中观测到的 SPW 相同。同时，我们发现证据表明，极地纬度的中层超波波是由纵向变化的重力波阻力原位产生的，并且存在由纵向变化的重力波阻力和中纬度地区的不稳定性混合产生的原位产生。基于观察，我们的结果表明上述三种机制可以同时起作用，这证实了早期的模型研究。此外，还讨论了副热带中间层异常强烈的SPW对同一冬季准两年期振荡（QBO）破坏的可能贡献或影响。
Abstract. The midwinter 2015/2016 was characterized by an unusually strong polar night jet (PNJ) and extraordinarily large stationary planetary wave (SPW) amplitudes in the subtropical mesosphere. The aim of this study is, therefore, to find the origin of these mesospheric SPWs in the midwinter 2015/2016 study period. The study duration is split into two periods: the first period runs from late December 2015 until early January 2016 (Period I), and the second period from early January until mid-January 2016 (Period II). While the SPW 1 dominates in the subtropical mesosphere in Period I, it is the SPW 2 that dominates in Period II. There are three possibilities explaining how SPWs can occur in the mesosphere: (1) they propagate upward from the stratosphere, (2) they are generated in situ by longitudinally variable gravity wave (GW) drag, or (3) they are generated in situ by barotropic and/or baroclinic instabilities. Using global satellite observations from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) the origin of the mesospheric SPWs is investigated for both time periods. We find that due to the strong PNJ the SPWs were not able to propagate upward into the mesosphere northward of 50 ∘ N but were deflected upward and equatorward into the subtropical mesosphere. We show that the SPWs observed in the subtropical mesosphere are the same SPWs as in the mid-latitudinal stratosphere. Simultaneously, we find evidence that the mesospheric SPWs in polar latitudes were generated in situ by longitudinally variable GW drag and that there is a mixture of in situ generation by longitudinally variable GW drag and by instabilities at mid-latitudes. Our results, based on observations, show that the abovementioned three mechanisms can act at the same time which confirms earlier model studies. Additionally, the possible contribution from, or impact of, unusually strong SPWs in the subtropical mesosphere to the disruption of the quasi-biennial oscillation (QBO) in the same winter is discussed.