Factors Controlling Precipitation Stable Isotopes in Qinghai-Tibet Plateau Transitional Area, China

In this study, we systematically explored the environmental significance of stable isotope characteristics and the controlling factors of precipitation stable isotopes in the source region of the Three Rivers (SRTR), the transitional zone of the Qinghai-Tibet Plateau in China. A total of 862 precipitation samples were collected from six fixed-point sampling locations between 2019 and 2021 in the SRTR. In June, the values of hydrogen (δD) and oxygen (δ¹⁸O) stable isotopes were most enriched. The deuterium-excess (d-excess) in atmospheric precipitation was > 0 in the SRTR; however, the maximum value of d-excess occurred in October. Moreover, the slopes of the local meteoric water line (LMWL) for Dari, Zaduo, Maduo, Qumalai, and Tuotuohe sites were lower than those of the global meteoric water line (GMWL). In contrast, the slope of the LMWL for Zhimenda was higher than that of the GMWL. The altitude effects of oxygen (δ¹⁸O) and hydrogen (δD) isotopes of precipitation were 0.70‰/100 m and 5.22‰/100 m, respectively. When the temperature was ≤ 5 °C, there was a significant temperature effect on stable oxygen isotope of precipitation (0.24‰/°C, P < 0.05). Furthermore, even a minor increase (1%) in the weight of raindrops after falling results in a 0.82% rise in the evaporation enrichment rate of δ¹⁸O. Successive precipitation events also had a substantial influence on precipitation in the transitional region of the Qinghai-Tibet Plateau. The results of this study provide a theoretical basis for revealing the impact mechanism of precipitation in the transitional zone of the Qinghai-Tibet Plateau under a warming climate.