Fine-scale characteristics of hourly intense rainfall in pre-summer and post-summer rainy seasons in Guangdong Province over coastal South China

Based on the hourly rainfall data from 86 national-level meteorological observation stations in Guangdong Province over coastal South China during 2000–2019, this study emphatically investigates the fine-scale characteristics of hourly intense rainfall (HIR) events, defined as greater than 20 mm/h, for the pre-summer and post-summer rainy seasons separately. Results show pronounced spatiotemporal characteristics of HIR events in rainy seasons, with similar maximum value regions as annual-mean rainfall. In particular, the HIR events occur most frequently in the Yangjiang area of western Guangdong, urban areas of Pearl River Delta, and the Shanwei area of eastern Guangdong in the pre-summer rainy season, while HIR events occur most frequently in the Leizhou Peninsula, Yangjiang region of western Guangdong and Haifeng-Jiexi regions of eastern Guangdong in the post-summer rainy season. Furthermore, there exist significant diurnal variation differences in the frequencies and rainfall amounts of HIR events between the pre-summer and post-summer rainy seasons. Two peaks appear in the pre-summer rainy season for the averaged diurnal variation of HIR events and show great differences in different HIR high-frequent regions. However, only one peak occurs in the post-summer rainy season, which mainly concentrates on the periods of afternoon hours with relative consistencies in different HIR high-frequent regions. The occurrence time of the diurnal maximum in HIR events frequency in the pre-summer rainy season presents a quadrupole spatial distribution from north to south, with the periods of the afternoon-to-evening, before dawn-to-morning, afternoon-to-evening, and before dawn-to-morning, respectively, while it has a banding distribution from coast to inland in the post-summer rainy season, with the near coastline occurring in before dawn and the inland in evening hours. These findings give a deeper understanding of the rainfall characteristics in Guangdong and can help to improve disaster prevention and mitigation capabilities.