Tides are one of the basic types of ocean water motions. Previous studies have reported that the M₂ constituent exhibits seasonal variations (annual cycles) in some regions. However, based on the newly proposed method of modified two-step harmonic analysis (HA) and its application at 240 global tide gauges, we find that the M₂ constituent as well as the S₂ and K₁ do not have significant seasonal variations at these tide gauges. The seasonal variations of the M₂ constituent reported in previous studies are caused by its satellites, the H₁ and H₂ constituents, which are not resolved in these studies due to the short time window (one month or three months) used in HA. Because the frequency of the H₁ (H₂) constituent is equal to that of the M₂ minus (plus) the frequency of annual cycles, the superposition of the M₂, H₁ and H₂ constituents with constant amplitudes is equivalent to the M₂ constituent with seasonally varying amplitudes. Compared with the new method, some adaptations to traditional HA aiming to capture variations in amplitudes and phase lags of constituents have some limitations, because they either neglect some satellites of the major constitutes or introduce spurious fluctuations resulting from an unreasonably large number of independent points. The nodal modulations of predominant constituents are also explored in this study. On the global scale, the nodal modulations of the M₂, K₁ and O₁ constituents agree with the theoretical predictions, except a cold spot region with reduced nodal modulation in the Gulf of Maine and a hot spot region with enhanced nodal modulation in the South China Sea for the M₂. Nodal modulation is also found for the S₂ constituent (in theory, the S₂ has no nodal modulation), which is 0.8% averaged at 164 tide gauges where the S₂ is not too weak.

潮汐是海洋水运动的基本类型之一。先前的研究报告说，M ₂成分在某些地区表现出季节性变化（年周期）。但是，基于新提出的改进的两步谐波分析（HA）方法及其在240个全球潮汐仪上的应用，我们发现M ₂成分以及S ₂和K ₁在_2月时没有明显的季节变化。这些潮汐计。先前研究中报告的M ₂成分的季节变化是由其卫星H ₁和H _{2引起的。}成分，由于HA使用的时间窗口较短（一个月或三个月），因此无法在这些研究中解决。因为H ₁（H ₂）成分的频率等于M ₂减去（加）年周期频率，所以具有恒定振幅的M ₂，H ₁和H ₂成分的叠加等于中号₂振幅随季节变化的成分。与新方法相比，针对传统HA的一些改进旨在捕获成分的幅度和相位滞后有一定局限性，因为它们要么忽略了主要成分的某些卫星，要么引入了由于不合理的大量独立点而导致的虚假波动。在这项研究中还探讨了主要成分的节点调制。在全球范围内，M ₂，K ₁和O ₁成分的节点调制与理论预测相符，除了缅因湾的节点调制降低的冷点区域和缅因州的节点调制增强的热点区域。 M ₂南海。还发现了针对S ₂成分的节点调制（理论上，S ₂没有节点调制），在S ₂不太弱的164个潮汐仪处平均为0.8％。