Future joint probability behaviors of precipitation extremes across China: Spatiotemporal patterns and implications for flood and drought hazards

摘要

Observed daily precipitation from 527 meteorology stations in China during 1960-2005, and simulated daily precipitation from five Earth System Models (ESMs) under historical, RCP2.6 and RCP8.5 scenarios from Coupled Model Intercomparison Project Phase 5 (CMIP5) datasets are analyzed to investigate joint probability behaviors of precipitation extremes in China during 2021-2050 and 2071-2100. Five joint return periods based on six extreme precipitation indices are defined. These joint return periods consider co-occurrence of extreme heavy and weak precipitation, as well as joint extreme heavy precipitation events in terms of different combinations of extreme precipitation amount, intensity, fractional contribution to annual precipitation days, and consecutive wet periods. Weather Generator Model (WGEN) is used to downscale the outputs of ESMs, and Copula is applied to construct joint probability distributions. The variations of joint return periods with 5-year marginal values (marginal values larger than their 5-year return period values respectively) and 20-year marginal values are discussed to represent changes in joint probability behaviors. Results show that: (1) during 1960-2005, spatial distributions of joint return periods with 5-year marginal values are similar to those with 20-year marginal values; (2) changes in marginal distributions and bivariate relationships between extreme indices may be the causes of joint probability distribution shift; (3) in general, during 2021-2050 and 2071-2100, there is less cooccurrence of consecutive wet and dry days, and more joint extreme heavy precipitation events with various aspects, implying less risk of co-occurrence of floods and droughts in the same year but higher risk of floods in China. But north China may face higher risk of co-occurrence of severe floods and droughts in the same year; and (4) changes in joint return periods under RCP8.5 are more remarkable than under RCP2.6. Even under RCP2.6, a scenario 2 ℃ global average warming target is met, the changes in joint return periods are still considerable.