The Temporal Evolution Characteristics of Extreme Rainfall in Shenzhen City, China

Global climate change has led to frequent urban flooding, and extreme rainfall has become the main cause of urban flooding due to its short duration and rapid occurrence. The study of the trend of extreme rainfall can provide an important reference for the prevention, control, and management of urban flooding. At present, there are abundant studies on the evolution characteristics of rainfall in Shenzhen, but there are relatively few studies on the evolution characteristics of extreme rainfall. To analyze the interannual variation in extreme rainfall in Shenzhen and provide a scientific basis for water resource management, this paper systematically analyses the interannual evolutionary characteristics and cyclical patterns of rainfall in Shenzhen based on the daily rainfall data of the city from 1958 to 2022 using the 3-year moving average method, linear regression model, Mann–Kendall mutation test, and wavelet analysis. Hurst index analysis was also used to predict the future trends of extreme rainfall and its frequency. The results indicate that the intensity and frequency of extreme rainfall in Shenzhen exhibit frequent fluctuations, with an overall slow downward trend and no sudden changes causing a decline. Periodic analysis reveals that extreme rainfall intensity and frequency exhibit significant wet–dry alternation characteristics on a time scale of 10–65 years, with the most prominent change occurring on a 63-year scale; in the main cycle, the wet–dry alternation cycle is about 44 years. The trend of the main cycle and wet–dry alternation cycle indicates that in recent years, the rainfall pattern in Shenzhen has developed towards short-term rainfall. The Hurst index analysis shows that the H values of extreme rainfall intensity and frequency are 0.666 and 0.631, respectively, both only slightly greater than 0.5, indicating weak positive persistence of the two indicators. This suggests that extreme rainfall events in Shenzhen may show a downward trend, but this trend does not have strong certainty.