Triple oxygen isotope compositions reveal transitions in the moisture source of West China Autumn Precipitation

The isotopic composition has long been used to investigate the factors influencing precipitation, whereas the variations of event-based precipitation isotopes caused by moisture transition and synoptic meteorological conditions remain limited. Here we present triple oxygen and hydrogen isotopes in event-based precipitation during West China Autumn Precipitation to evaluate the influence of various moisture sources in the hydrological process. Isotopes delta 18O, delta 17O, and delta D peak with convective precipitation at the onset stage, then drop to their lowest amid stratiform precipitation during the middle stage, and rise again towards the end. In contrast, Delta ' 17O levels remain elevated throughout the mid-stage of West China Autumn Precipitation compared to the onset and end stages. These isotopic variations, coupled with moisture analysis, reveal a distinct moisture source transition from the West Pacific Ocean to the westerly domain during West China Autumn Precipitation accompanied by the retreat of the Asian summer monsoon from Northwest China. Distinct moisture source transition from the West Pacific Ocean to the Westerly and inland domain occurred during West China Autumn Precipitation in Northwest China, according to event-based precipitation triple oxygen isotope data and moisture source analysis.