Abstract Being the very first SAR mode altimeter tandem phase, the Sentinel-3 A/B tandem phase has provided an unprecedented opportunity to better characterize the sensitivity of SAR altimetry retrievals to high-frequency processes, such as long ocean waves. In this paper, we show that for some sea-state conditions, that are still to be precisely characterized, long ocean waves are responsible for high-frequency (spatial and temporal) coherent Sea Level Anomaly (SLA) signals. It is found that the peak wavelength corresponds to the dominant swell wavelength. Furthermore, the short time lag between S3-A and S3-B acquisitions allows performing cross-spectral analyses that reveal phase shifts consistent with waves travelling according to the wave dispersion relation. It is also demonstrated that the classical 20 Hz sampling frequency is insufficient to properly sample most swell-induced SLA signals and that aliasing can generate errors over the entire frequency spectrum, including at long wavelengths. These results advocate for the use of azimuth oversampling (40 Hz or 80 Hz). Low-pass filtering should be applied prior to any down-sampling to 20 Hz, in order to prevent long-wavelength errors induced by spectral leakage.

中文翻译：

---

利用 Sentinel-3 串联相位数据集和方位角过采样更好地表征 SAR 高度计海面高度对长海浪的敏感性

摘要 作为第一个 SAR 模式高度计串联相位，Sentinel-3 A/B 串联相位为更好地表征 SAR 测高反演对高频过程（例如长海浪）的敏感性提供了前所未有的机会。在本文中，我们表明，对于一些仍有待精确表征的海况条件，长海浪负责高频（空间和时间）相干海平面异常 (SLA) 信号。发现峰值波长对应于主要膨胀波长。此外，S3-A 和 S3-B 采集之间的短时间延迟允许执行交叉光谱分析，揭示与根据波色散关系传播的波一致的相移。还证明了经典的 20 Hz 采样频率不足以正确采样大多数膨胀引起的 SLA 信号，并且混叠会在整个频谱上产生误差，包括长波长。这些结果提倡使用方位角过采样（40 Hz 或 80 Hz）。低通滤波应在任何降采样至 20 Hz 之前应用，以防止频谱泄漏引起的长波长误差。