Variations of Stable Isotopic Composition in Precipitation and their Controlling Factors, a Case Study in Dongying, Yellow River Delta

The stable isotopes of hydrogen and oxygen in precipitation provide a useful reference for the study of hydrological processes. However, the interpretation of stable isotopes in a monsoon climate zone remains uncertain. To investigate isotopic variations and the controlling factors in the midlatitude monsoon region, continuous observations of precipitation isotopes in Dongying were made. We investigate the controlling factors of precipitation δ¹⁸O by analyzing their relationship with temperature, precipitation amount, relative humidity, surface atmospheric pressure, and outgoing longwave radiation (OLR) data. Back trajectory analysis of the HYSPLIT model based on precipitation events was also used to trace moisture sources. The results show that there is a significant spatial correlation between stable isotopes of precipitation and precipitation amount in both monsoon and non-monsoon periods. The integration of large-scale convection over several days (0–10 days) preceding each event was determined as the main driver of precipitation isotopes in Dongying. The difference is that in the monsoon period, the isotope of precipitation records the convective activity of upstream water vapor in the past 10 days, while in the non-monsoon period, the precipitation isotope reflects the convective activity of upstream water vapor in the past 3 days. These findings improve regional-scale understanding of hydrological cycles in the East Asian mid-latitude monsoon region and have the potential to improve our understanding of isotopic variations in the proxy archives of the East Asian monsoon region.