Wave setup is a physical process that induces a temporal increase of the mean water level due to wave dissipation by bottom friction and breaking in the surf zone, extending over tens to hundreds of meters in the cross-shore direction. Wave setup contribution to coastal sea level solely induced by wind and atmospheric effects can increase by more than 100% under extreme events and conditions favoring its formation. It is therefore crucial to consider this phenomenon when assessing sea-level-related coastal hazards. Previous studies estimated the wave setup effect by means of numerical modeling and empirical formulations at regional and global scale. Such analyses require either high computational capacity to implement high-resolution numerical models over large domains, and/or accurate information on coastal morphological features from global or regional databases. Although the Mediterranean Sea is a fetch-limited environment, waves generated from extra-tropical cyclones are powerful enough for wave setup to develop, and subsequently for a potential significant wave setup contribution to extreme coastal sea level. Through the use of both numerical and empirical methods, we investigate the uncertainty associated to wave setup representation on the frequency and magnitude of coastal extreme sea levels occurring on sandy beaches in the Mediterranean Sea. Wave setup values are compared at beach scale between process-based modeling and empirical approaches, showing highly variable results. We also quantify the impact of wave setup on return levels of coastal sea level extremes using reconstructed sea levels. We employ various methods to calculate the wave setup component. Results show high spatial dispersion, with clear differences between the numerical and empirical approaches, especially in regions prone to the development of energetic waves. The total inter-method dispersion of 100-year return levels is often higher than 30 cm for average values of 62.4 cm. We emphasize the important limitations related to wave setup modeling (i.e., its underestimation) at large scale, and call for caution when applying empirical formulations (generally developed from local studies) at regional to global scale, which can lead to unrealistic wave setup values.

中文翻译：

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区域尺度的波浪设置估计：地中海的实证和基于模型的多方法分析


波浪形成是一种物理过程，由于底部摩擦力引起的波浪消散和冲浪区的破碎，导致平均水位暂时增加，并沿横岸方向延伸数十至数百米。在有利于其形成的极端事件和条件下，仅由风和大气效应引起的波浪形成对沿海海平面的贡献可能会增加 100% 以上。因此，在评估与海平面相关的沿海灾害时考虑这一现象至关重要。先前的研究通过区域和全球尺度的数值模型和经验公式来估计波浪设置效应。此类分析需要高计算能力以在大范围内实施高分辨率数值模型，和/或来自全球或区域数据库的关于沿海形态特征的准确信息。尽管地中海是一个取水有限的环境，但温带气旋产生的波浪足够强大，足以形成波浪的形成，并随后对极端沿海海平面产生潜在的重大波浪形成贡献。通过使用数值和经验方法，我们研究了与地中海沙滩上发生的沿海极端海平面的频率和幅度的波浪设置表示相关的不确定性。在海滩尺度上比较基于过程的建模和经验方法之间的波浪设置值，显示出高度可变的结果。我们还使用重建的海平面来量化波浪设置对沿海海平面极端值返回水平的影响。我们采用各种方法来计算波浪设置分量。 结果显示出较高的空间分散性，数值方法和经验方法之间存在明显差异，特别是在容易产生能量波的区域。 100 年回报水平的总方法间离散度通常高于 30 厘米，平均值为 62.4 厘米。我们强调与大规模波浪设置模型（即其低估）相关的重要局限性，并呼吁在区域到全球范围内应用经验公式（通常由当地研究开发）时要小心，这可能会导致不切实际的波浪设置值。