Future risk of decadal megadrought events over eastern China based on IPO-constrained precipitation

A reliable projection of future risk of decadal megadrought is crucial to adaption and mitigation over eastern China in future climate changes. However, it’s difficult to forecast the time of megadrought, which is dominated by internal variability of the model. Using a 50-member ensemble of simulations from the Community Earth System Model Version 2 Large Ensemble (CESM2-LE), it is found that, under the medium-high emission scenario (i.e., SSP3-7.0), internal variability account for all the uncertainty of decadal precipitation variability over eastern China, and the interdecadal Pacific oscillation (IPO) could contribute about 30% to the internal uncertainty during future period (2021–2080). Finally, an emergent constraint based on IPO phase is applied to reduce the uncertainty of simulated precipitation and to forecast the future megadrought risk. The constrained precipitation changes show that northern China will experience a high megadrought risk in the 2050s–2060s, and Yangtze River Valley will experience a high megadrought risk in the 2030s–2040s. These will have great benefit to specific strategies of social infrastructure in the future.