A Regional Atmospheric Model Using the Spectral-Element Method

This paper introduces a limited-area version of the Korean Integrated Model (KIM), whose global counterpart has been used operationally by the Korea Meteorological Administration (KMA) for weather forecasting since 2020. A central component of the development is the formulation of a lateral boundary condition suitable for KIM’s spectral-element dynamical core. In this implementation, the physical variables are specified only along a single line of elements at the model domain boundary, with no additional buffer zones for horizontal differential calculations (such as the advection term). In a perfect-model experimental setup of a short-range forecasting testbed, the regional KIM exhibits the typical benefits of high resolution, aligning with recent advancements in regional-scale modeling. In a climate-modeling testbed, the regional solution reproduces observed atmospheric variables without discernible synoptic-scale drift even in the absence of global solution nudging. The results also indicate that relaxation toward a background field is likely nonessential in this implementation, suggesting better stability and predictive skill of a regional model with the spectral-element-based lateral boundary treatment.