Analysis of Comprehensive Index of Rainstorm Based on Copula Model --A Case Study in Wanzhou

Based on precipitation data from 1967 to 2019 in Wanzhou District, this study selected annual rainstorm depth, annual rainstorm intensity and annual rainstorm contribution as rainstorm factors, built two-dimensional joint distribution by using the Archimedean Copula function, and used RMSE, AIC, Bias and OLS test to confirm the optimal Copula function, in order to analyze the probability of rainstorm and joint characteristic of return period with many combined factors. Results showed that, Clayton Copula function is suitable for building the comprehensive index joint distribution model of annual rainstorm depth and annual rainstorm intensity as well as annual rainstorm intensity and annual rainstorm contribution, Frank Copula function is suitable for building the comprehensive index joint distribution model of annual rainstorm intensity and annual rainstorm contribution.The positive correlation between rainstorm factors can be reflected directly and clearly by Copula function, and the optimal Copula functions is suitable for analyzing the joint probability of rainstorm factors. The Copula function model can reflect various characteristics of rainstorm, the internal information heavy elements can be presented by the joint return period and co-occurrence return period, and the degree of precipitation concentration and intensity level of rainstorm can be reflected as well. Therefore, the Copula function can be used to effectively reflect the joint characteristic and comprehensive information of rainstorm.