Historical and future projected frequency of extreme precipitation indicators using the optimized cumulative distribution functions in China

Abstract

The cumulative distribution functions (CDFs) of extreme precipitation indices (EPIs) characterize the occurrence of extreme precipitation events, but some CDFs have been either exaggerated or underestimated. In this study, we selected the most suitable CDFs from ten commonly used functions (i.e., Normal, two- and three-parameter log-normal, extreme value type-I, generalized extreme value-GEV, Weibull, two-parameter Gamma, Pearson-III type, Poisson, and Pareto) for the site- and regional-specific EPIs in China and projected their changes under the Representative Concentration Pathways (RCP) 4.5 and 8.5 scenarios combined with 28 general circulation models (GCMs) in Coupled Model Inter-comparison Project phase 5. Using the most appropriate site-specific CDFs, the spatial and temporal variations of the nine EPIs for the historical and projected future periods at 10-, 20-, 50- and 100-year return periods were investigated. The results showed that the GEV, Pearson-III, three- and two-parameter log-normal were generally the best CDFs for the 9 EPIs in China. By comparing the results during 2021–2100 with 1961–2017, the return periods increased as the EPIs increased. It was especially apparent in southeast China where the annual mean precipitation was above 1300 mm. The increases of the trends were significant for EPIs (especially in northwestern China), including the maximum 1 day precipitation, number of heavy precipitation days, number of very heavy precipitation days, extremely wet days and annual total wet day precipitation. The simple daily intensity index increased in northeast China, decreased in western China, but had no significant change in other regions. The maximum 5-day precipitation and consecutive wet days decreased in most areas except western China. The consecutive dry days decreased in northern China and increased in southeast China. This study provides region- and site-specific optimal CDFs and return period information and reveals the spatiotemporal changes of 9 EPIs at different return periods of 10-, 20-, 50- and 100-years under the RCP 4.5 and RCP 8.5 scenarios for 2021–2100. The obtained results are useful for guiding disaster-prevention efforts in different regions of China.