ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Physical Oceanography
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1441840
• Development of generalized terrain-following FVCOM model for the steep terrain seas
Provisionally accepted
- 1Hohai University, Nanjing, China
- 2Jiangsu Maritime Institute, Nanjing, Jiangsu Province, China
- 3Digital Engineering Technology Research Center for Maritime Safety and Security,, Nanjing, China
- 4School of Meteorology and Oceanography, National University of Defense Technology, Nanjing, Jiangsu Province, China
- 5Jiangsu Province Surveying & Mapping Engineering Institute, Nanjing, China
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Among various vertical coordinate systems, the sigma coordinate-a terrain following approach fitted to seabed topography-has been most widely used in coastal and continental shelf seas. However, it can induce notable simulation errors in the baroclinic pressure gradient (BPG) and baroclinic currents over steep-sloped terrains. In this study, a continuous layer index function of λ was adopted as a generalized vertical coordinate to replace the sigma coordinate in the FVCOM model. By adapting seawater motion equations suitable for the λ coordinate system, multiple forms of vertical coordinates could be flexibly configured in the FVCOM model. We designed three types of generalized terrainfollowing coordinates combining conventional sigma and z coordinates for the FVCOM model (named FVCOM-gtsz) and proposed a BPG calculation scheme by subtracting the local average density stratification. Two sets of idealized seamount numerical simulation experiments demonstrated that the new coordinate systems all significantly reduced simulation errors in BPG and baroclinic currents around steep seamounts. Compared to the conventional method of subtracting area-averaged density stratification, the proposed BPG scheme more effectively eliminated errors caused by density stratification. The FVCOM-gtsz was implemented in the South China Sea, demonstrating competent capability in simulating circulation patterns, mesoscale eddy activities, and vertical thermal stratification. We have further investigated the feasibility of designing density-feature-informed hybrid coordinates based on the λ coordinate system, along with other vertical coordinate formulations, which can substantially improve the FVCOM model's adaptive operational capacity in coastal and shelf marine environments.
Keywords: FVCOM, λ coordinate, generalized terrain-following coordinate, baroclinic pressure gradient, Ocean circulation model
Received: 31 May 2024; Accepted: 11 Jul 2025.
Copyright: © 2025 Bu, Chen, Zhu, Zhang, Cao and Ding. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yang Chen, Jiangsu Maritime Institute, Nanjing, Jiangsu Province, China
Shouxian Zhu, Hohai University, Nanjing, China
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