A novel high resolution model without open boundary conditions applied to the China Seas: first investigation on tides

We developed a Global Ocean Circulation and Tide Model (GOCTM) with coarse grids in the open deep ocean degrading 'smoothly' into the highly resolved China Seas (CS) of refined grids to study the tides and circulation there. GOCTM is based on the framework of the Finite Volume approach for better mass conservation through improved transports across the discrete individual control volume. It also takes a full advantage of the geometric flexibility of unstructured mesh using a realistic global topography including the Arctic Ocean. The CS are given a special focus by refining the unstructured grids, but they are embedded into global domain naturally. Furthermore, GOCTM not only successfully avoids the treatment of the open boundaries, but also optimizes the trade-off between computational cost and model accuracy. Meanwhile, GOCTM is driven by the astronomical tide-generating potential and the secondary tide-generating potential directly, together with the wind stress and heat flux. GOCTM succeeds in reproducing the global eight principal tidal harmonic constants. Particularly, the simulated tidal results in the CS are improved compared to some other regional models with the discrepancy of 3.9 cm for M2 tide. This idea of GOCTM can also be referred for other regional ocean study.