Impacts of significantly rising typhoon rainfall on total rainfall in a typical basin of China's Southeastern coast

Due to regional effects of typhoon poleward migration and terrain influences, it is important to investigate the impacts of typhoon rainfall (TR) changes on total rainfall (R) across different timescales and their spatial heterogeneity. Understanding these impacts is essential for elucidating the evolution of hydrological processes and water resources in the Western Pacific under climate warming. Taking the Minjiang River Basin (MJB), the largest basin along the southeastern coast of China, as a case study, this study used daily rainfall from 78 stations and the fixed box approach to analyze TR changes at different timescales (annual, monthly and daily). It further examined the impacts of TR changes on R and their spatial heterogeneity over two intervals, 1976–1997 and 1998–2019. The results indicated that (1) both typhoon frequency and duration increased in the MJB, leading to a significant rise in TR, which was consistent with typhoon poleward migration in the Western Pacific. (2) The impacts of rising TR on R varied across timescales. It had little impact on annual R but a marked impact on upstream August R, with TR contributions rising by 10%–20%. It also markedly affected downstream extreme rainfall, with the typhoon-influenced ratio of annual maximum one-day rainfall rising by 20%. (3) The basin morphology, characterized by a broad upstream and a narrow downstream, along with the barrier effect of middle mountain ranges, helps explain the spatial heterogeneity of these impacts. These findings provide scientific guidance for flood control and water resources management.