A Spatially Dependent Nudging Method and Its Application to a Global Tide Assimilation.

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Bibliographic Details
Title:	A Spatially Dependent Nudging Method and Its Application to a Global Tide Assimilation.
Authors:	Liu, Li¹ (AUTHOR), Chen, Xue'en¹ (AUTHOR) xchen@ouc.edu.cn
Source:	Advances in Atmospheric Sciences. Dec2024, Vol. 41 Issue 12, p2464-2477. 14p.
Subject Terms:	Circulation models, Ocean, *Simulation methods & models
Abstract (English):	Tides represent a crucial dynamic process in the ocean and play a vital role in both marine and atmospheric studies; thus, accurate simulation of tidal processes is of the utmost importance in tidal circulation models. Based on the sequential data assimilation method and the concept of the Kalman gain matrix, this paper proposes a new nudging method with spatially dependent coefficients for tidal assimilation. The spatial-dependent nudging method not only retains the advantages of the traditional nudging method but also facilitates the direct determination of a more reasonable spatial distribution of nudging coefficients. Utilizing the M2 tidal constituent (the main lunar semidiurnal tide) as an illustration, we conducted assimilation experiments of sea-level data to the barotropic circulation and tide model to assess the global harmonic constants of the M2 constituent. The results demonstrate that the spatial-dependent nudging method successfully mitigates deviations of tidal phase lag. Following assimilation using the new method, the deviations of the M2 tidal amplitude and phase lag can be reduced by 47% and 18% compared to the traditional nudging method, respectively, while the respective values for the non-assimilated case are as much as 9% and 11%. We also applied the S-nudging method to realistic tidal simulations and noted a significantly enhanced effectiveness relative to traditional methods, making it highly valuable for modeling oceanic tidal circulations. [ABSTRACT FROM AUTHOR]
Abstract (Chinese):	摘要: 潮汐作为海洋中一个重要过程, 在海洋和大气研究中起着至关重要的作用, 因此在潮汐环流模型中准确模拟潮汐过程至关重要. 基于顺序数据同化方法和Kalman增益矩阵的概念, 本文提出了一种新的具有空间依赖系数的nudging方法用于潮汐同化. 具有空间依赖系数的nudging方法不仅保留了传统nudging方法的优点, 还能直接确定更合理的nudging系数的空间分布. 以M2潮汐分量为例, 我们进行了海平面数据同化实验, 评估了M2分量的全球调和常数. 结果表明, 具有空间依赖系数的nudging方法成功减小了潮汐迟角偏差. 使用新方法同化后, M2潮汐振幅和迟角的偏差分别比未同化情况减少了47%和18%, 并且与传统nudging方法相比, 分别减少了9%和11%. 我们还将S-nudging方法应用于实际潮汐模拟, 相对于传统方法, 其效果显著增强, 使其在海洋潮汐环流建模中具有很高的应用价值. [ABSTRACT FROM AUTHOR]
Database:	Energy & Power Source

Description
Abstract:	Tides represent a crucial dynamic process in the ocean and play a vital role in both marine and atmospheric studies; thus, accurate simulation of tidal processes is of the utmost importance in tidal circulation models. Based on the sequential data assimilation method and the concept of the Kalman gain matrix, this paper proposes a new nudging method with spatially dependent coefficients for tidal assimilation. The spatial-dependent nudging method not only retains the advantages of the traditional nudging method but also facilitates the direct determination of a more reasonable spatial distribution of nudging coefficients. Utilizing the M2 tidal constituent (the main lunar semidiurnal tide) as an illustration, we conducted assimilation experiments of sea-level data to the barotropic circulation and tide model to assess the global harmonic constants of the M2 constituent. The results demonstrate that the spatial-dependent nudging method successfully mitigates deviations of tidal phase lag. Following assimilation using the new method, the deviations of the M2 tidal amplitude and phase lag can be reduced by 47% and 18% compared to the traditional nudging method, respectively, while the respective values for the non-assimilated case are as much as 9% and 11%. We also applied the S-nudging method to realistic tidal simulations and noted a significantly enhanced effectiveness relative to traditional methods, making it highly valuable for modeling oceanic tidal circulations. [ABSTRACT FROM AUTHOR]
ISSN:	02561530
DOI:	10.1007/s00376-024-4062-5