Impacts of Climate Change and Land-Use Change on Summer Water Vapor Contribution in Eastern China Based on a Bayesian Isotopic Mixing Model

Abstract Water vapor transport plays an important role in hydrological processes, influencing water cycles at global and regional scales. Investigating the change in water vapor sources of precipitation is helpful to understand the precipitation change and its cause. Combining the Bayesian isotopic mixing model and the Hybrid Single-Particle Lagrangian Integrated Trajectory model, this study determines the contribution change of water vapor sources for precipitation and the difference of water vapor sources under different land use and cover in eastern China. The study estimated that the mean contributions of advection, evaporation, and transpiration vapor to summer precipitation during 1969–2017 are 80.3%, 5.1%, and 14.5%, respectively. Among the advection vapor, vapor from Eurasia and the western Pacific Ocean contributes most to the precipitation in North China and vapor from the Indian Ocean, South China Sea, and western Pacific Ocean contributes most in South China. The contribution of advection vapor to precipitation decreases at the rate of 0.7% decade −1 , while the contributions of evaporation and transpiration vapor increase at the rate of 0.2% and 0.5% decade −1 , respectively. Advection vapor contribution is the controlling factor of summer precipitation change, while local evaporation and transpiration vapor are also contributors. In addition, the contributions of evaporation and transpiration vapor to precipitation are influenced by land use and cover type. The contributions of evaporation and transpiration vapor to precipitation for large-proportion forests are higher than those for cultivated lands, while the contributions for small-proportion forests are lower than those for cultivated lands.