Seasonal Variations and Controls on Triple Oxygen and Hydrogen Isotopes in Precipitation—A Case Study From Monitoring in Southwest China

Abstract Precipitation δ 18 O has offered valuable insights into the evolution of the Asian monsoon. Recent researches focusing on precipitation Δ′ 17 O has enhanced our understanding by offering new perspectives beyond those of δ 18 O, revealing insights into vapor sources and continental recycling. Nevertheless, there remains a lack of interannual triple oxygen isotope data, particularly in the Asian monsoon region. In this study, we analyzed the triple oxygen isotopes and hydrogen isotopes in monthly precipitation samples collected from Chongqing in Southwest China between 2019 and 2022 A.D. Seasonal variations in δD, δ 18 O, δ 17 O, and d‐excess values were observed, with lower values during the rainy season and higher values during the dry season, highlighting the impact of changes in moisture sources and local meteorological conditions on seasonal shifts in δD, δ 18 O, and δ 17 O. While, mean Δ′ 17 O values were higher in rainy season and lower in dry season. Notably, during rainy season, there is a negative correlation between monthly Δ′ 17 O values and the RH of the vapor source area, as well as a positive correlation with d‐excess . Recalculated Δ′ 17 O values based on RH of oceanic moisture source, are higher than the measured values for this period, indicating the contribution of terrigenous moisture to precipitation in SW China. Precipitation Δ′ 17 O values provide a more precise reflection of changes in moisture source, continental recycling, and evapotranspiration processes that drive water cycling compared Integrating modeling works in future will facilitate the use of precipitation Δ′ 17 O values to quantify the impact of different moisture source on precipitation.