Submitted as: model evaluation paper
09 Jan 2023
Submitted as: model evaluation paper | 09 Jan 2023
Status: this preprint is currently under review for the journal GMD.

An internal solitary wave forecasting model in the northern South China Sea (ISWFM-NSCS)

Yankun Gong1, Xueen Chen2, Jiexin Xu1, Jieshuo Xie1, Zhiwu Chen1, Yinghui He1, and Shuqun Cai1,3,4 Yankun Gong et al.
  • 1State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
  • 2College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao, 266100, China
  • 3Institution of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 510301, China
  • 4University of Chinese Academy of Sciences, Beijing, 100049, China

Abstract. Internal solitary waves (ISWs) are a ubiquitous phenomenon in the dynamic ocean system, which play a crucial role in driving transport through turbulent mixing. Over the past few decades, numerical modelling became a vital approach to investigate the generation mechanism and spatial distribution of ISWs. The northern South China Sea (NSCS) has been treated as a physical oceanographic focus of ISWs in massive numerical studies since last century. However, there was no systematic evaluation of a reliable three-dimensional model about accurately reproducing ISW characteristics in the NSCS. In this study, we implement a three-dimensional ISW forecasting model in the NSCS and quantitatively evaluate the requirements of factors (i.e., model resolution, tidal forcing, and stratification selection) in precisely depicting ISW properties by comparing with observational data at a mooring station in the vicinity of the Dongsha Atoll. Firstly, the 500 m-resolution model can basically reproduce the principal ISW characteristics, while the 250 m-resolution model would be a better solution to identify wave properties, specifically increasing 40 % accuracy of predicting characteristic half-widths. Nonetheless, a 250 m-resolution model spends nearly fivefold computational resources of a 500 m-resolution model in the same model domain. Compared with the former two, the model with a lower resolution of 1000 m severely underestimates the nonlinearity of ISWs, resulting in an incorrect ISW field in the NSCS. Secondly, the model with eight (or thirteen) primary tidal constituents can accurately reproduce the real ISW field in the NSCS, while the one with four main harmonics (M2, S2, K1 and O1) would underestimate averaged wave-induced velocity for about 38 % and averaged mode-1 wave amplitude for about 15 %. Thirdly, the model with the initial condition of field-extracted stratification gives a better performance in predicting some wave properties than the model with climatological stratification, namely 13 % improvement of arrival time and 46 % improvement of characteristic half-width. Finally, background currents, spatially varying stratification and external (wind) forcing are discussed to reproduce a more realistic ISW field in the future numerical simulations.

Yankun Gong et al.

Status: open (until 06 Mar 2023)

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Yankun Gong et al.

Yankun Gong et al.


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Short summary
Internal solitary waves (ISWs) play a crucial role in mass transport and ocean mixing in the northern South China Sea. Massive numerical investigations have been conducted in this region, but there was no systematic evaluation of a three-dimensional model about precisely simulating ISWs. Here, an ISW forecasting model is employed to evaluate the roles of resolution, tidal forcing and stratification in accurately reproducing wave properties via comparing to field and remote-sensing observations.