Upcoming satellite missions will observe the sea surface height (SSH) fields at a very high spatial resolution, which has generated an urgent need to better understand how well geostrophy can represent the ocean current field at finer scales, particularly in coastal regions characterized by complex flow geometry. We conduct statistical and spectral analyses of high-resolution surface currents and SSHs off the Oregon coast to examine the relative contribution of geostrophy and ageostrophy in coastal ocean currents. We analyze forward numerical simulations based primarily on a regional ocean model (ROMS) and use regional observations of high-frequency radar (HFR)-derived surface currents and altimeter-derived geostrophic currents and a subset of global domain numerical simulations (MITgcm) as secondary resources. Regional submesoscale ageostrophic currents account for up to 50% of the total variance and are primarily associated with near-inertial currents and internal tides. Geostrophy becomes dominant at time scales longer than 3 to 10 days and at spatial scales longer than 50 km, and is dependent on the depth and distance from the coast in the cross-shore direction. Ageostrophy dominates in the near-inertial and super-inertial frequency bands, which correspond to near-inertial motions (Coriolis force dominates) and high-frequency internal waves/tides (pressure gradient dominates), respectively. Because of ageostrophy, it may not be possible to estimate submesoscale currents from SSHs obtained from upcoming satellite missions using the geostrophic relationship. Thus, other concurrent high-resolution in-situ observations such as HFR-derived surface currents, together with data assimilation techniques, should be used for constructive data integration to resolve submesoscale currents.

即将进行的卫星任务将以非常高的空间分辨率观察海面高度 (SSH) 场，这迫切需要更好地了解地转如何在更精细的尺度上代表洋流场，特别是在以复杂流为特征的沿海地区几何学。我们对俄勒冈海岸附近的高分辨率地表洋流和 SSH 进行统计和光谱分析，以检查地转和地转对沿海洋流的相对贡献。我们分析主要基于区域海洋模型 (ROMS) 的正向数值模拟，并使用高频雷达 (HFR) 衍生的表面流和高度计衍生的地转流的区域观测以及全球域数值模拟 (MITgcm) 的子集作为次要资源。区域亚中尺度地转洋流占总方差的 50%，主要与近惯性洋流和内部潮汐有关。地转在时间尺度超过 3 至 10 天和空间尺度超过 50 公里时占主导地位，并且取决于跨岸方向到海岸的深度和距离。地转在近惯性和超惯性频带中占主导地位，分别对应于近惯性运动（科里奥利力占主导地位）和高频内波/潮汐（压力梯度占主导地位）。由于地转，可能无法使用地转关系从即将到来的卫星任务中获得的 SSH 估计亚中尺度电流。因此，