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Abstract:
The stable isotopic composition of rainwater (δ18Op and δDp) has been considered an effective proxy in studying atmospheric circulation and hydrological cycle processes. However, the linkage between variabilities in moisture sources and δ18Op remains poorly understood in Southwest China. Here, we utilized three long-term (10-year) δ18Op records (Beibei, Furong, and Yangkou stations) in Chongqing, Southwest China, from 2010 to 2019 A.D., integrated with a cluster analysis based on the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) to quantitatively demonstrate the close remote coupling of moisture sources and δ18Op on seasonal and interannual timescales. The clustering calculation results indicated that the percentage initial moisture source proportions of the westerlies and Asian summer monsoon have changed significantly at seasonal and interannual timescales, leading to the significant variation in δ18Op in Southwest China. Domination of westerlies and inland moisture contribution resulted in the positive δ18Op excursion in the dry season (November, December, January–April) while prevailing oceanic moisture led to the negative δ18Op excursions in the rainy season (May–October). On the interannual scale, δ18Op and d-excess exhibited a persistent positive/high trend, which is consistent with a decrease/increase in water vapor contributions from the ocean/westerly sources. Furthermore, δ18Op showed a good correlation with the Indian Ocean Dipole index, El Niño-Southern Oscillation, and the South Asian monsoon index, indicating that large-scale circulation patterns may affect regional δ18Op through their influence on moisture transport and convective activity in the source region. The long-term observation confirmed changes in moisture sources largely depend on the Westerly and Indian monsoon dynamics controlled by ocean-atmosphere circulation, supporting the effects of moisture sources on the rainwater isotopic composition.
