Microwave electromagnetic signals from the Global Navigation Satellite System (GNSS) are affected by their travel through the atmosphere: the troposphere, a non-dispersive medium, has an especial impact on the measurements. The long-term variations of the tropospheric refractive index delay the signals, whereas its random variations correlate with the phase measurements. The correlation structure of residuals from GNSS relative position estimation provides a unique opportunity to study specific properties of the turbulent atmosphere. Prior to such a study, the residuals have to be filtered from unwanted additional effects, such as multipath. In this contribution, we propose to investigate the property of the atmospheric noise by using a new methodology combining the empirical mode decomposition with the Hilbert–Huang transform. The chirurgical “designalling of the noise” aims to filter both the white noise and low-frequency noise to extract only the noise coming from tropospheric turbulence. Further analysis of the power spectrum of phase difference can be performed, including the study of the cut-off frequencies and the two slopes of the power spectrum of phase differences. The obtained values can be compared with theoretical expectations. In this contribution, we use Global Positioning System (GPS) phase observations from the Seewinkel network, specially designed to study the impact of atmospheric turbulence on GPS phase observations. We show that (i) a two-slope power spectrum can be found in the residuals and (ii) that the outer scale length can be taken to a constant value, close to the physically expected one and in relation with the size of the eddies at tropospheric height.

中文翻译：

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利用 GPS 相位差观测确定大气外尺度湍流长度：Seewinkel 网络

来自全球导航卫星系统 (GNSS) 的微波电磁信号会受到它们穿过大气层的影响：对流层是一种非色散介质，对测量有特别的影响。对流层折射率的长期变化延迟了信号，而其随机变化与相位测量相关。来自 GNSS 相对位置估计的残差的相关结构为研究湍流大气的特定特性提供了独特的机会。在进行此类研究之前，必须从不需要的附加影响（例如多径）中过滤掉残差。在此贡献中，我们建议使用将经验模式分解与 Hilbert-Huang 变换相结合的新方法来研究大气噪声的特性。手术式的“噪声设计”旨在过滤白噪声和低频噪声，仅提取来自对流层湍流的噪声。可以进一步分析相位差的功率谱，包括截止频率和相位差功率谱的两个斜率的研究。获得的值可以与理论预期进行比较。在此贡献中，我们使用来自 Seewinkel 网络的全球定位系统 (GPS) 相位观测，专门设计用于研究大气湍流对 GPS 相位观测的影响。我们表明（i）可以在残差中找到双斜率功率谱，并且（ii）可以将外部尺度长度取为一个恒定值，