Increased Occurrence and Intensity of Consecutive Rainfall Events in the China's Three Gorges Reservoir Area Under Global Warming

Consecutive rainfall events (CREs) are important triggers of geological hazards like landslide downhill and mudslide in the Three Gorges Reservoir area (TGR), China. These hazards are not only potential risks for the effective storage capacity of the reservoir but also threats of the safety of the reservoir's Great Dam. The future changes of CREs' occurrence and intensity are analyzed by using the projection experiments from 20 models attending the Coupled Model Intercomparison Project Phase 5 (CMIP5) under three different representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5). Spring and fall are focused on, during which CREs are most frequent. Considering a common overestimate of rainy days number in the state-of-the-art models, a new approach is developed to define CREs based on the percentile of rainfall distribution in observations. The approach yields a similar CREs climatology in models to that in observations and thus is used to identify CREs in models. The results based on multiple model ensemble (MME) and model spread comparison suggest a significant increase in spring and an overall decrease in fall in CREs' occurrence under all three scenarios. As for the intensity, it is projected to intensify in both spring and fall. Particularly, the higher the emission scenario, the greater the spring accumulated rainfall amount during a single CRE. These results imply an increasing risk of geological hazards in the TGR in the future.