Satellite altimetry and gravimetry are used to determine the mean seasonal cycle in relative sea level, a quantity relevant to coastal flooding and related applications. The main harmonics (annual, semiannual, terannual) are estimated from 25 years of gridded altimetry, while several conventional altimeter “corrections” (gravitational tide, pole tide, and inverted barometer) are restored. To transform from absolute to relative sea levels, a model of vertical land motion is developed from a high-resolution seasonal mass inversion estimated from satellite gravimetry. An adjustment for annual geocenter motion accounts for use of a center-of-mass reference frame in satellite orbit determination. A set of 544 test tide gauges, from which seasonal harmonics have been estimated from hourly measurements, is used to assess how accurately each adjustment to the altimeter data helps converge the results to true relative sea levels. At these gauges, the median annual and semiannual amplitudes are 7.1 cm and 2.2 cm, respectively. The root-mean-square differences with altimetry are 3.24 and 1.17 cm, respectively, which are reduced to 1.93 and 0.86 cm after restoration of corrections and adjustment for land motion. Example outliers highlight some limitations of present-day coastal altimetry owing to inadequate spatial resolution: upwelling and currents off Oregon and wave setup at Minamitori Island.

卫星测高和重力测量用于确定相对海平面的平均季节周期，这是一个与沿海洪水和相关应用相关的数量。主要谐波（年度、半年度、年度）是从 25 年的网格高度测量中估计出来的，同时恢复了几个传统的高度计“校正”（重力潮汐、极潮和倒置气压计）。为了从绝对海平面转换为相对海平面，垂直陆地运动模型是根据卫星重力测量估计的高分辨率季节性质量反演开发的。每年地心运动的调整说明在卫星轨道确定中使用质心参考系。一组 544 个测试潮汐计，从每小时测量中估计季节性谐波，用于评估对高度计数据的每次调整有助于将结果收敛到真实的相对海平面的准确程度。在这些仪表上，年和半年振幅的中位数分别为 7.1 厘米和 2.2 厘米。与测高的均方根差分别为 3.24 和 1.17 厘米，在恢复陆地运动的校正和调整后分别减小到 1.93 和 0.86 厘米。由于空间分辨率不足，异常值示例突出了当今沿海测高的一些局限性：俄勒冈州的上升流和洋流以及南鸟岛的波浪设置。在恢复校正和调整陆地运动后，它们减少到 1.93 和 0.86 厘米。由于空间分辨率不足，异常值示例突出了当今沿海测高的一些局限性：俄勒冈州的上升流和洋流以及南鸟岛的波浪设置。在恢复校正和调整陆地运动后，它们减少到 1.93 和 0.86 厘米。由于空间分辨率不足，异常值示例突出了当今沿海测高的一些局限性：俄勒冈州的上升流和洋流以及南鸟岛的波浪设置。