Impact of Global Warming on Extreme Rainfall in Taiwan

The relationship between global warming and extreme rainfalls in Taiwan was examined in this study. Taiwan rainfall data from TCCIP, a project led by MOST, were analyzed. North Hemisphere reference temperature data from NCEI led by NOAA. The yearly maximum of daily rainfall was focused on and the PGEV model, as proposed by Olafsdottir et al. \citep{olafsdottir2021extreme}, was used to fit the extreme values and make inferences. The PGEV model integrates the General Extreme Value (GEV) and Peak over Threshold (PoT) approaches, which are commonly used to analyze extreme data. Relative intensity and return value were used to show the connection between temperature and extreme rainfall. Results indicated that the intensity of extreme rainfall in Taiwan increases as the temperature rises. However, the effects of global warming on the frequency and intensity of extreme rainfalls varied by region. In the north and south regions, the frequency of extreme rainfalls changed, while in the center and east regions, the intensity of extreme rainfalls changed. Furthermore, according to the return value analysis, extreme rainfalls are likely to occur more frequently in the future. To account for differences between locations, Gaussian Process was used to smooth the results obtained using the PGEV model. In addition, simulations using the Gaussian copula and Gaussian Process were conducted to determine the quantile confidence intervals for each PGEV model. The simulations showed that all tests comparing with models with and without covariates are significant.