Preprints
https://doi.org/10.5194/egusphere-2023-2905
https://doi.org/10.5194/egusphere-2023-2905
06 Dec 2023
 | 06 Dec 2023
Status: this preprint is open for discussion.

An analytical model investigating the impact of current shear and topographic fluctuations on surface waves

Meng Sun, Yongzeng Yang, Xunqiang Yin, Jisheng Ding, Tianqi Sun, and Nan Jia

Abstract. There are interactions between surface waves and currents, the latter includes wind-driven current and tidal current. Currents influence surface waves though advection transport and shear instability generation processes. While the horizontal gradient of current is commonly considered to calculate wave-current interaction source term in most wave models, the vertical gradient of current (current shear) has been simplified. In coastal waters, strong background currents with topographic fluctuations at the scale of surface waves have a resonance effect on surface waves. However, this resonance process is currently ignored in existing wave models. To evaluate the effects of current shear and topographic fluctuations on surface waves more accurately, an analytical model is proposed to describe the modification of the amplitude of orbital velocities for surface waves. The amplitude of orbital velocities exhibits significant variations when considering both current shear and topographic fluctuation effects. Wave particle trajectory equations that incorporate current shear and topographic fluctuations are derived based on this analytical model. In deep waters, current shear can increase or decrease the horizontal radius of wave particle trajectory by approximately 0.3 m, while the modification of horizontal amplitude of orbital velocities is about 0.3 m/s. In shallow waters, with both topographic fluctuations and background current present, both horizontal and vertical radii of wave particle trajectory change by approximately ±0.1 m respectively, and the modification of both horizontal and vertical amplitudes of orbital velocities is about 0.2–0.3 m/s. Moreover, in some cases, there are reversals in the direction of wave particle trajectories.

Meng Sun, Yongzeng Yang, Xunqiang Yin, Jisheng Ding, Tianqi Sun, and Nan Jia

Status: open (until 26 Feb 2024)

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  • RC1: 'Comment on egusphere-2023-2905', Anonymous Referee #1, 05 Jan 2024 reply
  • RC2: 'Comment on egusphere-2023-2905', Anonymous Referee #2, 18 Feb 2024 reply
Meng Sun, Yongzeng Yang, Xunqiang Yin, Jisheng Ding, Tianqi Sun, and Nan Jia
Meng Sun, Yongzeng Yang, Xunqiang Yin, Jisheng Ding, Tianqi Sun, and Nan Jia

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Short summary
The understanding of wave-current interactions is important for comprehending the dynamics of the ocean. Among them, the mechanisms of vertical shear of background current and topographic fluctuations are two research issues with limited attention. In this study, based on the unified wave theory, an analytical model is proposed to describe the modification of the amplitude of orbital velocities for surface waves in presence of background current and topographic fluctuations.