Assessment of Dynamical Downscaling Performance over CORDEX East Asia using MPAS-A Global Variable Resolution Model: Climatology, Seasonal Cycle, and Extreme Events

Abstract

Abstract A 29-year variable resolution climate simulation is conducted from January 1988 to December 2016 using the Model for Prediction Across Scale-Atmosphere (MPAS-Atmosphere) with prescribed sea surface temperatures obtained from ERA-Interim reanalysis. The global variable resolution configuration employed a mesh refinement of 92-25km centered over East Asia (MPAS-A experiment, hereafter), which could preserve multi-scale features within the same model framework. The evaluation of MPAS-A is performed for precipitation, near-surface air temperature, and circulation features against observed climate using combined observational datasets. The MPAS-A experiment exhibited large-scale deviations due to the absence of observational constraints, especially for the northward displacement of rain belts, excessive rainfall over the tropical ocean, and stationary surface air temperature biases tied to specific regions. These deviations can be explained by the simulated circulation, moisture transports, and the relationship between precipitation and convective available potential energy (CAPE). While the simulated seasonal cycles and frequency are dominated by large-scale deviation patterns, certain climate indices demonstrated lower sensitivity in the refined regions, particularly regarding extreme rainfall. This finding underscores the robustness and potential of the variable resolution (VR) approach in obtaining regional information within a single model framework.