Title: 陰陽格子の開発 Title: The "Yin-Yang Grid": A Chimera Grid for the Spherical Geometry Author: 陰山 聡 Key words: Yin-Yang grid, overset grid, Chimera grid Abstract: An overset grid or a Chimera grid is proposed for the spherical geometry. It is named "Yin-Yang Grid" since it reminds us the Chinese philosophical symbol (or its three-dimensional version). The Yin-Yang grid is composed of two component grids. They are identical in the shape and the coordinates. The component grid is just the low latitude region of the usual spherical latitude-longitude grid. The grid spacing of the Yin-Yang grid is nearly uniform and it has no coordinate singularity. The Yin-Yang grid is applied to geoscientific three-dimensional simulations including geodynamo, mantle convection, atmosphere and ocean simulations.