Comparative analysis of extreme precipitation simulations over China by CMIP6 and CMIP5 models: similarities, differences, and uncertainty assessment

This study compares CMIP6 and CMIP5 in simulating extreme precipitation over China against observations, and projects future changes under SSP245 (2046–2065) and SSP585 (2080–2099) scenarios. The results indicate that CMIP6 and CMIP5 exhibit similar spatial distributions large-scale spatial distributions during the reference period. However, significant regional differences are observed. CMIP6 shows improvements in southern, central, eastern, and northwestern China (SC, CC, EC, NC), while CMIP5 performs better in southwestern, northeastern China (SWC, NEC) and the Tibetan Plateau (TP). Under future scenarios, both ensembles project robust increases in extreme precipitation, intensifying with higher emissions. Notably, CMIP6 also simulates significantly higher extreme precipitation in SC and SWC compared to CMIP5, while lower values are projected in NWC and TP, creating a distinct dipole pattern of change. The analysis of model biases reveals that their influence on future projections is highly region-dependent, with no clear trend for China as a whole. Finally, the underestimation of southwesterly moisture transport from the Arabian Sea and Bay of Bengal, along with the overestimation of mid-latitude westerlies is identified as a key factor contributing to the underestimation of precipitation in southern Region (SR) and overestimation in northern Region (NR) by both CMIP6 and CMIP5.