Limited-Area Version of the Korea Integrated Model for the High-Resolution Regional Forecast System

This presentation introduces the limited-area version of the Korean Integrated Model (KIM). KIM is a global atmospheric weather prediction model which has been operational in producing medium-range forecasts for the Korea Meteorological Administration since 2019. In efforts to develop a high-resolution short-range forecasting system for the Korean Peninsula and East Asia, we developed a model framework capable of running KIM as a limited-area model (LAM). The LAM version shares model components with the global KIM model, including the cubed-sphere grid system, spectral element method solver, non-hydrostatic dynamical core, and scale-aware physics package; with the distinction that the model domain is confined to the first panel of the cubed-sphere. The related modules to accommodate this configuration in the model framework has been newly developed accordingly. Utilizing the Schmidt transformation of the cubed-sphere enables adjustment of the size and center position of the first panel through stretching and rotating the cube. The functionality of the LAM framework is demonstrated through idealized dynamics-only test runs nesting global KIM simulations. In real-case dynamical downscaling experiments refining 100 km global simulations to 25 km, the LAM exhibits stable simulations beyond 10 days of integration, closely aligning with global simulation results. Minimal generation of numerical spurious waves is observed, even without utilizing Newtonian-relaxations toward the global simulation near the lateral boundaries, suggesting the effectiveness of dynamical cores with spectral element solvers for dynamical downscaling. The presentation also addresses challenges related to high computational costs, sensitivities to varying domain size and resolution, and the model's applicability to operational kilometer-scale short-range weather prediction.