Accelerated LMARS Shallow Water Model with a Stretched Cubed Sphere Grid at Sub-km Scales

The pursuit of global kilometer-scale modeling in atmosphere science presents a dual challenge: comprehensive models become computationally prohibitive and analytically intractable, while idealized models lack essential physical forcing, creating a critical gap in atmospheric research. To bridge this divide, this work develops and validates the innovative ACC-LMARS-SW model, a novel theoretical framework designed for efficient, high-resolution global atmospheric dynamics studies. The model features three synergistic innovations. First, its physics kernel introduces real-world topography and a real-world-equivalent season-aware radiative forcing scheme into the shallow-water equations, significantly enhancing physical realism while retaining conceptual clarity. Second, it employs a variable-resolution stretched cubed-sphere grid that concentrates computational resources on regions of interest , achieving sub-kilometer local resolution without prohibitive global cost. Third, the dynamical core is fully redesigned for massive parallelism using the OpenACC standard, leveraging the efficiency of the Low-Mach Approximate Riemann Solver (LMARS) to harness GPU acceleration.

A suite of numerical experiments demonstrates the model's capabilities. 1) Mesh efficacy: Stretched-grid simulations show reduce error in target areas compared to uniform-resolution runs in classic tests, better resolving nonlinear eddy interactions. 2) Physical fidelity: A global simulation at ~1.5 km average resolution (with ~500 m over the South China Sea) forced by real topography and idealized radiation spontaneously generates a horizontal kinetic energy spectrum featuring distinct  k^-3 and k^-5/3 power-law segments , which is a hallmark of real atmospheric scale interactions. 3) Computational performance: GPU implementation achieves up to a 70x speedup versus estimated serial CPU execution, making global kilometer-scale theoretical experiments feasible on a single workstation.

In conclusion, ACC-LMARS-SW successfully integrates algorithmic design, mesh technology, and high-performance computing to create an efficient and physically insightful "numerical laboratory." This approach provides the high resolution and computational efficiency needed to study fundamental multi-scale dynamics, such as cross-scale energy transfer, dynamical responses to orography, and mesoscale eddy dynamics.