An ocean circulation model in sigma S-z-sigma B hybrid coordinate and its validation

作者：Zhuang Zhanpeng^*; Yuan Yeli; Yang Guangbing

来源：Ocean Dynamics, 2018, 68(2): 159-175.

DOI：10.1007/s10236-017-1124-6

• Ocean circulation model
• sigma S-z-sigma B hybrid coordinate
• Baroclinic gradient forces calculation
• Quasi-global numerical experiment
• Two-time-level difference schemes

A 3D, two-time-level, sigma S-z-sigma B hybrid-coordinate Marine Science and Numerical Modeling numerical ocean circulation model (HyMOM) is developed in this paper. In HyMOM, the sigma coordinate is employed in the surface and bottom regions, and the z coordinate is used in the intermediate layers. This method can overcome problems with vanishing surface cells and minimize the unwanted deviation in representing bottom topography. The connection between the sigma and z layers vertically includes an expanded "ghost" method and the linear interpolation. The governing equations in the sigma S-z-sigma B hybrid coordinate based on the complete Reynolds-averaged Navier-Stokes equations are derived in detail. The two-level time staggered and Eulerian forward and backward schemes, which are of second-order of accuracy, are adopted for the temporal difference in internal and external mode, respectively. The computation of the baroclinic gradient force is tested in an analytic test problem; the errors for two methods in HyMOM, which are relatively large only in the bottom layers, are obviously smaller than those in the pure sigma and z models in almost all of the vertical layers. A quasi-global climatologic numerical experiment is constructed to test the simulation performance of HyMOM. With the monthly mean Levitus climatology data as reference, the HyMOM can improve the simulating accuracy compared with its pure z or sigma coordinate implementation.

• 出版日期2018-2
• 单位国家海洋局第一海洋研究所