Tracking Moisture Sources of Precipitation Over China

Moisture of precipitation originates from terrestrial and oceanic evaporation through atmospheric transport. Understanding the contributions from different moisture sources to precipitation is essential for the hydrologic study. China is the world's third largest country in terms of land area and has contributed 25% of the global net increase in vegetation leaf area since 2000. Thus, it provides a good platform to understand the contributions from different moisture sources to precipitation and how increasing vegetation greenness affects precipitation trends. In this study, we investigated the moisture sources of precipitation and their changes in China during 1980-2018 based on the UTrack moisture recycling data set. We found that 47.3% of the moisture was from oceanic evaporation, and 52.7% was from terrestrial evapotranspiration (ET). For the moisture from terrestrial ET, 33.0% was from vegetation transpiration. The observed annual precipitation showed a significant increasing trend with 2.07 mm/year in China from 1980 to 2018. Increasing moisture from oceanic evaporation contributed the most to the increasing precipitation trend (0.98 mm/year), followed by the increasing moisture from vegetation transpiration (0.72 mm/year) and other terrestrial evaporation (0.37 mm/year). The increasing contribution of vegetation transpiration from China was comparable with that from neighboring countries (0.37 vs. 0.35 mm/year). The increasing moisture from vegetation transpiration could be due to the nationwide afforestation projects in China since 1999. The results provide a reference for understanding changes in precipitation and hydrologic processes. Precipitation plays a crucial role in the water cycle, and changes in precipitation have significant impacts on the water cycle. Understanding the contributions from different moisture sources to precipitation is essential for water resources research. In this study, we found that 47.3% of the precipitation in China originated from oceanic moisture, 33.0% was from vegetation transpiration, and 19.7% was from other terrestrial moisture sources. Increasing moisture from oceanic evaporation contributed the most to the precipitation trend in China, followed by the increasing moisture from vegetation transpiration. The increasing moisture from vegetation transpiration could be due to the nationwide afforestation projects in China since 1999. The results provide a reference for understanding changes in precipitation and contribute to better water resources management.