Impact of Multiple High-resolution Regional Domains on the Accuracy of the Global Surface Tides

The predictability of the global surface tides in a relatively low-resolution global parent domain can be improved through two-way nesting with a high-resolution regional child domain. However, the improvement significantly depends on the location of the child domain as well as its domain size. In this study, we investigate how important the number of child domains and their locations is for improving the accuracy of the global tides in the global ocean model HYCOM. Seven 1/75⁰ child domains are nested in the 1/25⁰ global parent domain using OASIS3-MCT. We compare the numerical results to tidal gauge data, and global tidal solutions such as TPXO8-atlas and FES2014. As the number of child domains increases, the tidal accuracy in the parent domain gets improved more. The accuracy of the M2 barotropic tide with seven child domains is more than 70% of the stand-alone 1/75⁰ global simulation. We also compare the computational costs of two-way nesting cases to the stand-alone 1/25⁰ and 1/75⁰ simulations on the Unite States Navy's supercomputers. In addition, we study the effect of spatially varying wave drag in the child domains to maximize the improvement by two-way nesting.