Atmospheric gravity waves (GWs) are a critically important dynamical mechanism in the terrestrial atmosphere, with significant effects on weather and climate. They are geographically ubiquitous in the middle and upper atmosphere, and thus, satellite observations are key to characterising their properties and spatial distribution. Nadir-viewing satellite instruments characterise the short horizontal wavelength portion of the GW spectrum, which is important for momentum transport; however, these nadir-sensing instruments have coarse vertical resolutions. This restricts our ability to characterise the 3D structure of these waves accurately, with important implications for our quantitative understanding of how these waves travel and how they drive the atmospheric circulation when they break. Here, we describe, implement and test a new spectral analysis method to address this problem. This method is optimised for the characterisation of waves in any three-dimensional data set where one dimension is of coarse resolution relative to variations in the wave field, a description which applies to GW-sensing nadir-sounding satellite instruments but which is also applicable in other areas of science. We show that our new “2D + 1 ST” method provides significant benefits relative to existing spectrally isotropic methods for characterising such waves. In particular, it is much more able to detect regional and height variations in observed vertical wavelength and able to properly characterise extremely vertically long waves that extend beyond the data volume.

中文翻译：

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利用垂直相位差更好地解析3D重力波结构

大气重力波（GWs）是地球大气中极其重要的动力机制，对天气和气候具有显着影响。它们在中层和高层大气中在地理上无处不在，因此，卫星观测是表征它们的特性和空间分布的关键。天底观测卫星仪器表征了引力波光谱的短水平波长部分，这对动量传输很重要；然而，这些最低点传感仪器的垂直分辨率很粗糙。这限制了我们准确表征这些波的 3D 结构的能力，对我们定量理解这些波如何传播以及它们在破裂时如何驱动大气环流具有重要意义。在这里，我们描述，实施并测试一种新的光谱分析方法来解决这个问题。该方法针对任何三维数据集中的波表征进行了优化，其中一维相对于波场的变化具有粗分辨率，这种描述适用于 GW 传感天底探测卫星仪器，但也适用于其他科学领域。我们展示了我们新的“2D +  1 ST”方法相对于表征此类波的现有光谱各向同性方法具有显着优势。特别是，它更能够检测观测到的垂直波长的区域和高度变化，并能够正确表征超出数据量的极垂直长波。