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Abstract The rapidly increasing computing powers allow global atmospheric simulations with aggressively high resolutions, challenging traditional model design principles. This study presents a Low Mach number Approximate Riemann Solver (LMARS) based unstaggered finite‐volume model for solving the shallow‐water equations on arbitrary gnomonic cubed‐sphere grids. Using a novel reference line‐based grid‐generation process, it unifies the representation of arbitrary gnomonic cubed‐sphere grid projections and permits high‐efficiency 1D reconstruction in the halo regions. The numerical discretization also extends a widely used pressure gradient algorithm with the LMARS viscous term, thus improves the model's stability for various numerical applications. The solver demonstrates a broad range of organic diffusion control without any explicit filters, validated by a comprehensive set of test cases. Lastly, a newly introduced splash on the sphere test verifies the solver's desirable dispersion properties and consistent performance among different grid types. This study paves a solid foundation for a new generation of global circulation models with kilometer horizontal scales.
Xi Chen (Sat,) studied this question.