Kelvin‐Helmholtz Billow Interactions and Instabilities in the Mesosphere Over the Andes Lidar Observatory: 1. Observations
Kelvin‐Helmholtz Billow Interactions and Instabilities in the Mesosphere Over the Andes Lidar Observatory: 1. Observations
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DOI：
10.1029/2020jd033414
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
J. Hecht;D. Fritts;L. Gelinas;R. J. Rudy;R. Walterscheid;A. Z. Liu
中科院分区：
文献类型：
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作者：
J. Hecht;D. Fritts;L. Gelinas;R. J. Rudy;R. Walterscheid;A. Z. Liu
2016 年 2 月，智利 Cerro Pachón 的安第斯山脉激光雷达天文台安装了一台非常高的空间分辨率（90 km 高度约 25 m 像素）OH 气辉成像仪。该仪器与 Na 风温激光雷达搭配使用。 2016年3月1日，激光雷达数据显示，在世界标准时间0100之前，大气是动态不稳定的，因此有利于形成开尔文-亥姆霍兹不稳定性（KHI）。成像仪显示存在 KHI 和视大气重力波 (AGW)，其传播大致垂直于主要 KHI 运动平面。 AGW 似乎诱导了剪切层的调制，导致新兴 KHI 巨浪的错位。这些使得强大的 KHI 波涛相互作用成为可能，因为它们实现了大振幅并随后快速过渡到湍流。这种相互作用表现为早期在实验室研究中发现的涡管和结特征，如 Thorpe (1987, https://doi.org/10.1029/JC092iC05p05231; 2002, https://doi.org/10.1002/qj.200212858307) 中所讨论的，并根据在对流层云，但在以前的高层大气观测中从未被识别过。这项研究首次对这些 KHI 相互作用动力学进行了高分辨率气辉成像观察，这些相互作用驱动了湍流的快速转变，并表明了这些动力学在中层和其他高度的潜在重要性。对这些动力学进行建模的配套论文（Fritts 等人，2020 年，https://doi.org/10.1029/2020JD033412）证实，相对于单个 KHI 波涛的内部不稳定性，涡管和结产生更快速且显着增强的湍流。
A very high spatial resolution (∼25 m pixel at 90 km altitude) OH airglow imager was installed at the Andes Lidar Observatory on Cerro Pachón, Chile, in February 2016. This instrument was collocated with a Na wind‐temperature lidar. On 1 March 2016, the lidar data showed that the atmosphere was dynamically unstable before 0100 UT and thus conducive to the formation of Kelvin‐Helmholtz instabilities (KHIs). The imager revealed the presence of a KHI and an apparent atmospheric gravity wave (AGW) propagating approximately perpendicular to the plane of primary KHI motions. The AGW appears to have induced modulations of the shear layer leading to misalignments of the emerging KHI billows. These enabled strong KHI billow interactions, as they achieved large amplitudes and a rapid transition to turbulence thereafter. The interactions manifested themselves as vortex tube and knot features that were earlier identified in laboratory studies, as discussed in Thorpe (1987, https://doi.org/10.1029/JC092iC05p05231; 2002, https://doi.org/10.1002/qj.200212858307) and inferred to be widespread in the atmosphere based on features seen in tropospheric clouds but which have never been identified in previous upper atmospheric observations. This study presents the first high‐resolution airglow imaging observation of these KHI interaction dynamics that drive rapid transitions to turbulence and suggest the potential importance of these dynamics in the mesosphere and at other altitudes. A companion paper (Fritts et al., 2020, https://doi.org/10.1029/2020JD033412) modeling these dynamics confirms that the vortex tubes and knots yield more rapid and significantly enhanced turbulence relative to the internal instabilities of individual KHI billows.