Separating typhoon and non-typhoon rainfall reveals structural shifts in coastal-to-inland basins

초록

Long-term hydrological change in typhoon-prone coastal-to-inland river basins presents growing challenges for flood risk assessment under a changing climate. Here, we develop a generalizable basin-scale diagnostic frame work that separates typhoon and non-typhoon rainfall, embeds them in a Budyko-based runoff analysis, and quantifies spatially heterogeneous hydrological sensitivities applicable to coastal-to-inland systems worldwide. As a proof-of-concept demonstration, we apply this framework to the Qiantang River Basin (QRB), eastern China, a representative typhoon-prone coastal-to-inland basin influenced by the East Asian summer monsoon and Western North Pacific tropical cyclones. Using data from 11 stations during 1980-2020, the framework detects a precipitation-regime shift around 2009, after which annual rainfall increased by roughly 13-15% across sub basins and Budyko-estimated runoff potential also increased. The disproportionate runoff-potential increase in the coastal-adjacent Fuchun subbasin suggests possible amplification by land-surface modification and urbanization. Typhoon-related precipitation, though only about 6% of annual totals, increased by nearly 50% after 2009 and showed a disproportionate contribution to extreme rainfall, reaching 28% of extreme volumes in the coastal-adja cent subbasin, while inland extremes remained dominated by non-typhoon processes. These results demonstrate that long-term hydrological changes in typhoon-prone coastal-to-inland basins can manifest as structural regime shifts in both precipitation composition and runoff generation. More broadly, the explicit separation of typhoon and non-typhoon rainfall within a Budyko framework provides a physically grounded and transferable diag nostic tool readily applicable to other typhoon-prone basins globally, supporting flood-risk and water-resources management under ongoing climate change.

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