Definition of Extreme Rainfall Events and Design of Rainfall Based on the Copula Function

Extreme rainfall has changed in frequency and intensity as a result of climate change, and its impact on nature and society is far greater than that of rainfall change. Scientifically defining extreme rainfall events and obtaining the design rainfall is of great significance to analyze the impact of climate change on extreme precipitation events. Existing definitions of extreme precipitation events have usually focused on rainfall amounts at fixed durations rather than complete events with variable durations. Using sub-daily precipitation and runoff data covering 1971-2018 from 17 stations over the Jingle sub-basin, we constructed an appropriate copula function to define extreme persistent rainfall events under bivariate analysis and obtained the rainfall process of the designed rainfall under different return periods. The results showed that (1) the joint distribution based on Copula was more accurate than the traditional univariate probability methods for identifying extreme rainfall events with a threshold of 90%. (2) The Copula joint distribution established in the basin can well calculate the designed extreme rainfall under the return periods of 100 a, 50 a, 30 a, 25 a, 10 a and 5 a. (3) The rainfall intensity duration model had a good simulation effect on the rainfall intensity duration distribution of the basin.