Pole relocation for an orthogonal grid: An analytic method

Oceanic general circulation models, especially for climate applications, lack computational efficiency and accuracy when solved on horizontal grids that contain a singularity, i.e. a grid pole, within the ocean mask of the computational domain. Here we present a fully analytical approach of generating a curvilinear, globally orthogonal grid, where the grid poles are located outside the ocean's computational domain, and the grid parallels in the vicinity of the geographic Equator are parallel to the latter. The grid is dipolar, asymmetric and composite with a smooth transition. In this grid all ocean basins are connected and straits are open in the same manner as on the geographical grid. The grid generation is based on grid parallels which are circles and the analytical determination of grid meridians which are orthogonal to them. Grid-cell anisotropy and grid resolution are determined from analytical functions, and may be varied to suit scientific goals.