Development and Evaluation of the Dynamic Framework of an Ocean General Circulation Model with Arbitrary Orthogonal Curvilinear Coordinate

In this study, an ocean model dynamical framework applicable to general horizontal orthogonal curvilinear coordinate is developed. It is implemented in a climate system ocean model LICOM2.0 (LASG/IAP Climate system Ocean Model, version2.0) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS). Using the latitude-longitude coordinate, simulation results with the new dynamical framework and the original one used in the LICOM2.0 are identical. Based on the new dynamical framework, the ocean model exploits the "so-called" tripolar grid that is capable of describing the topography of the Arctic Ocean accurately, which helps to eliminate the shortcoming that the North Pole is treated as an isolated island in the LICOM2.0 standard version. Therefore, the model's performance in simulating the circulation in the Arctic Ocean and the Atlantic Meridional Overturning Circulation (AMOC) has been improved significantly. Additionally, introducing the tripolar grid can also avoid computational instability caused by the drastic decrease of grid interval with increasing latitude. In the tripolar grid version of LICOM2.0, the model can achieve computational stability without applying any space filtering technique. Accordingly, the model's parallel efficiency has been greatly improved compared with the standard version of LICOM2.0. It is especially true when the model's horizontal resolution increases to 0.1 degree, as the parallel acceleration ratio of the ocean model can be increased from 5.8 in the standard latitude-longitude grid version to about 15.0 in the tripolar grid version.