Processes affecting isotopes in precipitation of an arid region

Quantifying recycled moisture fraction in precipitation of an arid region using deuterium excess

An accurate representation of the spatial distribution of stable isotopes in modern precipitation is vital for interpreting hydrological and climatic processes. Considering the dominant impact of moisture sources in controlling water isotopes and deuterium excess, we conducted a meta-analysis of precipitation isotopes using instrumental data from 68 stations around China. The entire country is divided into five regions according to the major moisture sources: Region I (the westerlies domain), Region II (the arctic domain), Region III (the northeast domain), Region IV (the Pacific domain), and Region V (the Tibetan Plateau). Each region has unique features of spatial distribution and seasonal variation for stable precipitation isotopes and deuterium excess. In particular, seasonal variation in Region IV tracks the onset of Asian summer monsoons well. The regional meteoric water lines are presented for each region. A significant temperature effect is found in Regions I and III, with δ18O-temperature gradients of 0.13–0.68‰/°C and 0.13–0.4‰/°C, respectively. However, the reasons for the temperature effects are quite different. In Region I, this effect is caused by the seasonal shift of the westerlies, whereas in Region III, it is caused by the seasonal difference in moisture sources. The precipitation amount effect is most significant in the region along the southeast coast in China, where the δ18O-precipitation amount the gradient is −0.24 to −0.13‰/mm. The findings in our paper could serve as a reference for isotopic application in hydrological and paleo-climatic research.