title: The ``Yin-Yang Grid'': An Overset Grid in Spherical Geometry

author: Akira Kageyama and Tetsuya Sato

abstract:

A new kind of overset grid, named Yin-Yang grid, 
for spherical geometry is proposed.
The Yin-Yang grid is composed of two identical
component grids that are combined
in a complemental way to cover a spherical surface
with partial overlap on their boundaries.
Each component grid is a low latitude part
of the latitude-longitude grid.
Therefore the grid spacing is quasi-uniform
and the metric tensors are simple and analytically known.
One can directly apply 
mathematical and numerical resources that have been written
in the spherical polar coordinates or latitude-longitude grid.
The complemental combination of the
two identical component grids enables us to 
make efficient and concise programs.
Simulation codes for geodynamo and mantle convection simulations
using finite difference scheme based on the Yin-Yang grid are
developed and tested.
The Yin-Yang grid is suitable for massively parallel computers.