A nonhydrostatic oceanic regional model, ORCTM v1, for internal solitary wave simulation

Abstract

Abstract. The Oceanic Regional Circulation and Tide Model (ORCTM), including a nonhydrostatic dynamics module which can numerically reproduce internal solitary wave (ISW) dynamics, is presented in this paper. The performance of a baroclinic tidal simulation is also examined in regional modeling with open boundary conditions. The model control equations are characterized by three-dimensional and fully nonlinear forms considering incompressible Boussinesq fluid in Z coordinates. The pressure field is decomposed into the surface, hydrostatic, and nonhydrostatic components on the orthogonal curvilinear Arakawa-C grid. The nonhydrostatic pressure determined by the intermediate velocity divergence field is obtained via solving a three-dimensional Poisson equation based on a pressure correction method. Model validation experiments for ISW simulations with the topographic change in the two-layer and continuously stratified ocean demonstrate that ORCTM has a considerable capacity for reproducing the life cycle of internal solitary wave evolution and tide–topography interactions.

A Pressure Projection Scheme With Near‐Spectral Accuracy for Nonhydrostatic Flow in Domains With Open Boundaries

“…While the excitation of the internal tide can be reasonably captured by regional ocean models, its subsequent nonlinear steepening leads to nonhydrostatic wave trains of O(100) m scale that propagate 100s of kilometers. Fully non‐hydrostatic simulation of such waves on the basin scale is currently not feasible (Huang et al., 2023; Simmons et al., 2011) due to the computational expense of solving the three‐dimensional elliptic equation for nonhydrostatic pressure. In addition, there is increasing interest in simulations of upper ocean dynamics that can capture portions of both the inverse oceanic energy cascade as well as the forward cascade toward small, dissipative scales, which is thought to be initiated at 1–10 km horizontal scales (Balwada et al., 2022), enhanced at frontal structures (Srinivasan et al., 2023), and accomplished by nonhydrostatic internal wave energy transfers (Marino et al., 2015).…”