Spatiotemporal evaluation of CMIP6 extreme precipitation indices across major river basins in South Korea

초록

This study evaluates the performance of 30 Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating extreme precipitation across five major river basins in South Korea from 1975 to 2010. A multi-metric framework combining spatial bias analysis, Kling-Gupta Efficiency, Taylor diagrams, and Kernel Density Estimation was applied to seven ETCCDI indices. Results from spatially averaged basin-scale annual time series indicate significant upward trends in precipitation intensity and frequency, particularly for PRCPTOT (5.55 mm/year), R95p (5.75 mm/year), and Rx1day (0.56 mm/year). Trend magnitudes vary among basins, reflecting South Korea's topographic complexity. In contrast, CDD exhibits a slight decline. Within the model ensemble, BCC-CSM2-MR, GFDL-CM4, and GISS-E2-1-G exhibited the highest proficiency in representing the magnitude and climatological variability of these extreme events. Nevertheless, considerable regional discrepancies remain, including a consistent overestimation of total precipitation in southern coastal areas and an underestimation of extreme intensity indices. These results indicate that, although CMIP6 models capture long-term hydroclimatic trends, region- and index-specific bias correction is recommended for reliable climate impact applications.

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