Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage
Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage
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DOI：
10.5194/acp-17-8553-2017
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发表时间：
2017-07
影响因子：
6.3
通讯作者：
C. Wright;N. Hindley;L. Hoffmann;M. Alexander;N. Mitchell
中科院分区：
文献类型：
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作者：
C. Wright;N. Hindley;L. Hoffmann;M. Alexander;N. Mitchell
抽象的。重力波在大气中传输动量和能量，对全球大气环流产生深远的影响。因此，准确测量它们对于了解大气和开发下一代天气预报和气候预测模型至关重要。然而，事实证明，从卫星测量中测量全套GW参数非常困难，卫星测量是唯一适合全球覆盖的观测。这一点在接近南纬60°的纬度地区尤为关键，因为那里的气候模型明显低估了波动量通量。在这里，我们提出了一种新的全3-D的方法，用于检测和表征在平流层GW。该方法是基于周围的3-D斯托克韦尔变换，并可以追溯到现有的观测数据。这是第一次科学地使用这种光谱分析技术。我们将我们的方法应用于高分辨率的3-D大气温度数据从AIRS/Aqua在海拔范围20-60公里。我们的方法使我们能够确定检测到的每个波的参数范围很广。这些包括振幅、传播方向、水平/垂直波长、高度/方向分辨的动量通量（MF）以及相速度和群速度矢量。后三个以前从未从单个卫星仪器测量过。我们在南安第斯山脉和南极半岛周围的地区证明了这种方法，这是60° S带附近最大的GW MF已知来源。我们的分析表明，存在强间歇性的高度定向聚焦的全球Ws具有非常高的动量通量（在30公里的高度为100 -100 mPa或更高）。这些波浪与山脉密切相关，而不是德雷克海峡的开阔海洋。测得的通量是直接正交的山脉，符合地形源机制，在冬季是最大的。此外，我们对波群速度矢量的测量显示了明确的观测证据，这些波强烈地集中在极地夜间风喷流中，因此可能对这些纬度的动量缺失有重大贡献。这些结果证明了我们的新方法的能力，它为提供下一代天气和气候模型所需的观测提供了强大的工具。
Abstract. Gravity waves (GWs) transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20–60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs), and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60° S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (∼ 80–100 mPa or more at 30 km altitude). These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity vectors show clear observational evidence that these waves are strongly focused into the polar night wind jet, and thus may contribute significantly to the missing momentum at these latitudes. These results demonstrate the capabilities of our new method, which provides a powerful tool for delivering the observations required for the next generation of weather and climate models.