Abstract: A new region-split method is established on the basis of the characteristicdirection method, which is easy to be implemented on the barotropic shallow water modelwhose region is the Sphere or Hemisphere. This method has three advantages. First,theboundary conditions on the common boundary of the split regions need no special treatment.because the boundaries of the split regions can tally naturally on the common boundaryNext,using the natural periodic boundary condition along the meridional direction in then...