| Summary: | Abstract Tsunami propagation simulation over the full-global ocean with a finite-difference method is carried out using a grid rotation transformation in a latitude–longitude coordinate system. Two singular points (North/South Poles) that are antipodes with each other in the latitude–longitude coordinate are both moved to land using the grid rotation transformation. The moved singular points are also antipodes with each other. We provide algebra to represent the grid rotation and propose two candidates of the moved singular points for practical use. One is that the computational North Pole is moved to China, and the other is the computational pole moved to Greenland. We carry out tsunami propagation simulation over the global ocean for the different candidates of the moved singular points and evaluate numerical errors due to the grid rotation transformation. The numerical errors are found to be more reduced with finer resolution of the spatial grid for the simulation. When the spatial resolution is fixed, the numerical errors are reduced over most regions for the case with the computational North Pole moved to Greenland, more than the case with the pole moved to China. We indicate that the Coriolis force effect on the tsunamis that was expected to be minor even in far fields becomes significant after long propagation (>~1 day). Tsunami simulation, Global ocean, Grid rotation
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