Development and validation of a global 1∕32° surface-wave–tide–circulation coupled ocean model: FIO-COM32

Abstract

Model resolution and the included physical processes are two of the most important factors that determine the realism or performance of ocean model simulations. In this study, a new global surface-wave–tide–circulation coupled ocean model FIO-COM32 with a resolution of 1/32∘ × 1/32∘ is developed and validated. Promotion of the horizontal resolution from 1/10 to 1/32∘ leads to significant improvements in the simulations of surface eddy kinetic energy (EKE), the main paths of the Kuroshio and Gulf Stream, and the global tides. We propose the integrated circulation route error (ICRE) as a quantitative criteria to evaluate the simulated main paths of the Kuroshio and Gulf Stream. The non-breaking surface-wave-induced mixing (BV) is proven to still be an important contributor that improves the agreement of the simulated summer mixed-layer depth (MLD) against the Argo observations even with a very high horizontal resolution of 1/32∘. The mean error in the simulated mid-latitude summer MLD is reduced from −4.8 m in the numerical experiment without BV to −0.6 m in the experiment with BV. By including the global tide, the global distributions of internal tide can be explicitly simulated in this new model and are comparable to the satellite observations. Based on Jason-3 along-track sea surface height (SSH), wavenumber spectral slopes of mesoscale ranges and wavenumber frequency analysis show that the unbalanced motions, mainly internal tides and inertia-gravity waves, induced SSH undulation and are a key factor for the substantially improved agreement between model and satellite observations in the low latitudes and low-EKE regions. For the ocean model community, surface waves, tidal currents and ocean general circulations have been separated into different streams for more than half a century. This paper demonstrates that it is time to merge these three streams for a new generation of ocean model development.