Recent studies have revealed that the predominant tidal constituents have seasonal variations at some locations. However, how to accurately obtain these variations remains a problem for the traditional harmonic analysis (HA) due to the tradeoff between length of time window and resolution of constituents. Therefore, a method named as “two-step HA” is developed in this study, which consists of both long- and short-time-window HA. Through a series of ideal experiments, practical application at two tidal gauges and comparison with the traditional HA, the feasibility and accuracy of the two-step HA are verified: The two-step HA performs better than the traditional HA in estimating monthly amplitudes and phases for the predominant constituents, whether they have seasonal variability or not. In addition to capturing variations of the predominant constituents at tidal gauges, the two-step HA would be useful in investigation of the coherence and incoherence of internal tides.

中文翻译：

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两步谐波分析可捕获主要潮汐成分的季节性变化幅度和相位滞后

最近的研究表明，主要的潮汐成分在某些地方具有季节性变化。然而，由于时间窗的长度与成分的分辨率之间的折衷，如何精确获得这些变化仍然是传统谐波分析（HA）的问题。因此，本研究开发了一种称为“两步式高可用性”的方法，该方法包括长时窗和短时窗高可用性。通过一系列理想的实验，在两个潮汐仪上的实际应用以及与传统HA的比较，验证了两步HA的可行性和准确性：在估计每月振幅和相位方面，两步HA的性能优于传统HA。对于主要成分，无论它们是否具有季节性变化。