Downscaling Simulation Study of Regional Climate in China Since the Last Glacial Maximum

This study employs the iTraCE transient simulation results over the past 21,000 years as lateral boundary conditions, nested within the RegCM4.7 regional climate model, to perform high-resolution simulations of millennial-scale climate variations in the China region since the Last Glacial Maximum (LGM). The findings indicate that the RegCM model significantly ameliorates the temperature and precipitation biases associated with the coarse resolution of iTraCE, thereby providing a more accurate representation of regional climate dynamics during the observational period. Comparative analyses of temperature and precipitation trends across various periods since the LGM show that both the iTraCE and RegCM simulations successfully reproduce the climatic features of the LGM, characterized by a dry and cold climate, as well as the Holocene, which is characterized by a warm and wet climate, as reconstructed from proxy data. By contrasting the reconstructed records with the simulation outputs for four distinct regions of China—northern China, southern China, the Tibetan Plateau, and the northwest—this study explores the contribution of seasonal temperature variations to the discrepancies in the trends of Holocene mean annual temperature changes between the reconstructed records and simulations. In northern China, the Tibetan Plateau, and the northwest, the simulations suggest that mid-Holocene temperatures were higher than those in the late Holocene, although winter temperatures during the mid-Holocene were lower than those in the late Holocene, with a more pronounced seasonal temperature variation. In contrast, in southern China, the simulated mid-Holocene summer and winter temperatures were lower than those of the late Holocene, leading to differences in the trends of simulated and reconstructed mean annual temperatures. Notably, the reconstructed summer temperature changes were found to be in good agreement with the simulated summer temperature variations in northern and northwest China.