ASSESSMENT OF CMIP6 MULTI-MODEL SIMULATION OF SUBTROPICAL HIGH IN THE NORTHWESTERN PACIFIC OCEAN IN SUMMER

This study aims to systematically evaluate the performance of thirteen Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating the summertime Northwestern Pacific Subtropical High (NWPSH), with an emphasis on assessing their spatial patterns, climatological characteristics, and long-term trends.Results indicate that certain the CMIP6 models exhibit systematic biases in simulating the 500-hPa geopotential height over the Northwestern Pacific during summer, while performing better in capturing both the interannual variability and spatial amplitude modulation of the geopotential height field.By correcting these systematic biases using NCEP/NCAR observational data, the accuracy of simulations is significantly improved, particularly in depicting the NWPSH indexes and its spatial shape.Quantitative assessments identify EC-Earth3, EC-Earth3-Veg, BCC-ESM1, and MRI-ESM2-0 as superior in reproducing the NWPSH index.Further analysis using Shared Socioeconomic Pathways scenarios (SSPs) reveals distinct future trajectories for NWPSH intensity and spatial position, highlighting the importance of robust model selection for reliable future climate projections in East Asia.Overall, the findings of this study provide essential guidance for selecting and applying the CMIP6 models to improve the accuracy of regional climate change attribution analyses and future climate projections.