Airglow observations of dynamical (wind shear‐induced) instabilities over Adelaide, Australia, associated with atmospheric gravity waves
Airglow observations of dynamical (wind shear‐induced) instabilities over Adelaide, Australia, associated with atmospheric gravity waves
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DOI：
10.1029/2001jd000419
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发表时间：
2001-11
影响因子：
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通讯作者：
J. Hecht;R. Walterscheid;R. Vincent
中科院分区：
文献类型：
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作者：
J. Hecht;R. Walterscheid;R. Vincent
虽然近年来对大气重力波（AGW）气辉图像中的不稳定性特征进行了一些观测，但这种测量仍然很少。到目前为止，这些特征的特点是似乎是垂直于AGW波前对齐。多仪器观测证实了理论预测，即这些特征是由对流不稳定性引起的，其中AGW引起的温度变化导致总递减率超过绝热递减率。2000年2月，在澳大利亚的巴克兰公园进行了气辉观测，观测结果显示了具有不同特征的不稳定性特征。这些图像显示了小尺度（水平波长小于10公里）的特征，与较大尺度的AGW波前平行。这些特征仅在OH图像中出现，而在O2 A图像中没有出现，这表明它们起源于90公里海拔以下。同时中频雷达风数据显示存在的平均风切变，在小尺度功能期间，几乎对准AGW传播的方向。此外，更大规模的AGW接近90公里高度附近的临界水平。虽然风切变本身不足以引起不稳定，但对数据的分析表明，小尺度特征是87-90公里高度区域动态（风切变引起的）不稳定的结果。不稳定是由于背景风切变和大尺度AGW接近临界水平时通过引起的大切变共同作用的结果。
While several observations have been made in recent years of instability features in airglow images of atmospheric gravity waves (AGWs), such measurements are still rare. To date, these features are characterized by appearing to be aligned perpendicular to the AGW wave fronts. Multi-instrument observations confirm the theoretical prediction that such features are caused by convective instabilities where the AGW-induced temperature variation causes the total lapse rate to exceed the adiabatic lapse rate. In February 2000, airglow observations were obtained at Buckland Park, Australia, which showed instability features with a different characteristic. These images showed small-scale (less than 10 km horizontal wavelength) features aligned parallel to the larger scale AGW wave fronts. These features were only seen in OH images, not in O2A images, indicating that they originate below 90 km altitude. Simultaneous MF radar wind data reveal the presence of a mean wind shear which, during the period of the small-scale features, was aligned nearly in the direction of AGW propagation. In addition, the larger scale AGW approached a critical level near 90 km altitude. While the wind shear itself is not large enough to cause an instability, an analysis of the data suggests that the small-scale features are the result of a dynamic (wind shear-induced) instability in the 87–90 km altitude region. The instability was due to a combination of the background wind shear and the large shear induced by the passage of the larger scale AGW as it approached the critical level.