Projecting Extreme Wet‐Cold Events in Southern China Based on CMIP6 Experiments With Emergent Constraints of Observable Temperature Inversion

Abstract

Extreme wet‐cold events (WCEs), characterized by persistent freezing rain and/or heavy snowfall resulting in damage to power transmission, communication and transportation, are the most severe compound disasters during the cold season in southern China. In this study, we first analyzed the observational trend of WCEs using daily gauged precipitation and 2 m‐temperatures from 753 stations across mainland China from 1960 to 2020. The results show a decreasing trend in the total WCE days. Then the historical runs from the 26 models participating in Coupled Model Intercomparison Project Phase 6 (CMIP6) are analyzed, and the results suggest that the models can simulate this trend generally well but have a greater magnitude of reduction along with evident uncertainty. Thus, we constrain the CMIP6 models by using the lower‐tropospheric temperature inversion as the observable variable based on the emergent constraint. Five models are selected by this constraint, and their simulations significantly reduce the uncertainty in WCE projections, encompassing trend, intensity, occurrence, spatial extent, and duration, relative to the original 26 models. Accordingly, future changes in WCEs under two emission scenarios, SSP245 and SSP585, are projected based on constrained models. The results suggest that WCEs will intensify in the future, while their occurrence, spatial extent and duration will decrease. A further circulation mechanism analysis based on a self‐organizing map suggests that, alongside surface warming, changes in the optimal circulation patterns for WCEs help explain the projections. The finding that the intensity of WCEs will intensify in the future is of special importance for disaster preparedness.