This study spatially interpolates isotope data from nine stations in northwest China based on the LMDZ (Laboratoire de Météorologie Dynamique-Zoom) model, analyzes the contribution of different water vapor sources to precipitation in the region through a ternary mixing model, and simulates the trajectory of air mass transport in the region by combining with the HYSPLIT model. The results show that δ18O and δ2H in precipitation in northwest China are impoverished in winter and enriched in summer, and Xi'an, Yan'an, and Lanzhou show the characteristics of low summer and high winter due to the influence of the southeast monsoon. Spatially, they are relatively impoverished in the mountainous regions and enriched in the oasis and desert regions. Shaanxi station (45.56 %), Yinchuan (36.05 %), and Lanzhou (24.7 %) are influenced by the southeast monsoon in summer, and the rest of the stations are mainly from westerly water vapor (Mediterranean Sea, Black Sea, and Caspian Sea, etc.). All the water vapor in winter originates from the westerly wind belt. The contribution of external water vapor is the largest, exceeding 70 % at most stations, followed by plant evapotranspiration water vapor with 0.4-39.3 %, and surface evapotranspiration water vapor with the smallest contribution of 0.1-2.2 %. In addition, the strength of westerly belt transport affected the isotopic enrichment of external water vapor, and vegetation cover significantly regulated the rate of water vapor recirculation. This study not only offers new insights into the application of isotope modeling techniques in hydrology and water resources, but also provides crucial reference for optimizing water resource management and allocation in this region.
Yin et al. (Thu,) studied this question.