When the horizontal resolution becomes high in atmospheric general circulation model, the spectral method may have some difficulties for high performance computing: the Legendre transformation and extensive data movement between computer nodes on a massively parallel computer. On the other hand, when the simple latitude-longitude grid is used in the grid method, the pole problem, occurs. The grid spacing near the poles becomes very small as the resolution becomes high.

In order to radically overcome the pole problem, it is needed to use another type of grid which is distributed as homogeneously as possible on the sphere. The Next Generation Model Research Group in Frontier Research System for Global Change ( FRSGC ) has started to develop a new model based on the icosahedral geodesic grid, which is one of the quasi-homogeneous grids. Using the shallow water equations, we have overcome some difficulties in the icosahedral grid configuration[1].

When a simulation with high resolution in the horizontal direction is performed, the equation in the vertical dynamics should be also reconsidered from the usually used hydrostatic equation to the non-hydrostatic one. In almost of the existing non-hydrostatic models, the conservations of several important quantities are not completely satisfied. Since our purpose is on the global climate simulation, the conservations of mass and total energy are required. Our research group has been developing a new non-hydrostatic scheme, in which such properties are completely satisfied[2]. We apply this non-hydrostatic scheme to the global model based on the icosahedral grid configuration.

In this Workshop, we introduce the formulation of used scheme in our non-hydrostatic global model and show the first result. we also summarize the computational performance of our model on Earth Simulator.

[1] H.Tomita, M.Tsugawa, M.Satoh, and K.Goto (2001),"Shallow Water Model on a Modified Icosahedral Geodesic Grid by Using Spring Dynamics,'' J. Compt. Phys., vol.174, p.579

[2] M.Satoh (2002), "Conservative scheme for the compressible non-hydrostatic models with the horizontally explicit and vertically implicit time integration scheme,'' Mon. Wea. Rev., in press.