Isotopic analysis of precipitation during rainstorm and typhoon events from the warm season in the Southeastern Coast of China

Xiamen, located on China’s southeastern coast Under global climate change, Xiamen experiences frequent warm-season rainstorms, yet the influencing factors of such rainstorms along the southeastern coast have not been fully elucidated. This study investigates regional precipitation, utilizing hourly samples collected from April to July 2024. These samples are categorized into four types based on dominant weather systems: warm air mass, cold air mass, alternating warm-cold air masses, and typhoon-induced precipitation. Stable isotope (δ¹⁸O and d-excess) analyses are employed to explore δ¹ ⁸O patterns during events, precipitation type-specific controlling factors, and the correlation between d-excess changes and water vapor source shifts linked to wind direction variations. δ¹ ⁸O values consistently exhibit a decreasing-then-increasing trend during precipitation events. Controlling factors differ by type: warm air mass events are dominated by the amount effect; cold air mass events by temperature; alternating air masses by combined temperature and amount effects; and typhoon precipitation primarily by condensation and re-evaporation processes. D-excess changes strongly correlate with wind direction-linked vapor source shifts. These findings clarify distinct isotopic mechanisms driving coastal precipitation dynamics, enhancing understanding of extreme rainfall generation and providing a robust scientific basis for regional hydrological modeling and heavy precipitation prediction under climate change. • Isotope variation patterns differ significantly across different synoptic systems. • Wind direction shift is a key trigger for d-excess variation in precipitation. • δ¹⁸O values of all four rainstorm events show a U-shaped change pattern. • Isotope influencing factors differ between typhoons and ordinary rainstorms.