Multi-year average water vapor characteristics and potential sources and transport pathways of intense water vapor during extreme precipitation events in the Ili River Valley, China

Study region: Ili River Valley, China: Study focus: The spatial and temporal variations of water vapor content and precipitation conversion efficiency in the Ili River Valley from 1979 to 2022 are quantified using the reanalysis dataset, and the water vapor transport characteristics of the basin are investigated. Finally, potential water vapor sources, contributions, and transport pathways during extreme precipitation in the Ili Valley over the past 44 years are investigated using three backward trajectory methods. New hydrological insights for the region: The results show that the annual average water vapor content in the Ili River Valley is on an overall upward trend, with higher levels in the plains than in the mountainous areas, peaking at certain elevations before decreasing, and showing large regional fluctuations. The multi-year average water vapor content is primarily influenced by the transport from westerly winds, with the western boundary serving as the main water vapor input. Furthermore, the net water vapor budget has shown a slight upward trend over the past 44 years. Extreme precipitation mainly occurs in the eastern and southern mountains of the Ili River Valley, where the sources and transport pathways of water vapor exhibit similar patterns. The water vapor mainly originates from Central Asia, the Caspian Sea, the Black Sea and nearby inland areas. Moreover, localized water vapor transport within Xinjiang also has an important influence on extreme precipitation. The findings of this study are crucial for modeling and predicting extreme events and their spatial distribution, which can significantly reduce the risk of natural disasters triggered by extreme precipitation and provide a solid scientific basis for water resource management in the Ili River Valley.