Evolving relationships between atmospheric water vapor and precipitation over Europe under climate change

Abstract

Understanding how atmospheric water vapor translates into precipitation is fundamental to assessing future changes in the hydrological cycle under climate change. While integrated water vapor (IWV) is a key precursor of precipitation, the temporal stability of their relationship and its evolution under different climate scenarios remain uncertain, particularly at continental scales. In this study, we investigate long-term changes in the statistical relationship between precipitation and water vapor across Europe using an ensemble of Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model simulations. Historical and future projections under contrasting climate change scenarios were analyzed to examine how precipitation–vapor coupling evolves from the pre-industrial period through the end of the 21st century. To enable consistent comparison across regions and time periods, precipitation and IWV were transformed into standardized indices (Standardized precipitation index, Standardized integrated water vapor) based on probabilistic distributions. Correlation and cross-correlation analyses were then applied to quantify both the strength of coupling and the response times between precipitation and atmospheric water vapor. The results reveal pronounced regional differences in the precipitation–vapor relationship across Europe, with stronger coupling observed in parts of Western Europe compared to other regions. Under the Shared Socioeconomic Pathways 8.5, the precipitation–vapor relationship exhibits a tendency to weaken over time, suggesting a growing decoupling between precipitation and water vapor. In addition, precipitation responses were found to systematically lag changes in IWV by several weeks to months, highlighting the importance of considering temporal delays in hydroclimatic assessments. These findings provide new insights into the evolving dynamics of precipitation–vapor interactions under climate change and offer a basis for improving the interpretation of large-scale hydrological responses in climate model projections.

Keywords: Atmospheric Water Vapor, Precipitation, Precipitation-vapor Coupling, Climate Change, Cross-correlation, Europe

 

Acknowledgment

This research was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government (MSIT) (RS-2024-00334564 & RS-2021-NR060085), the Korea Environmental Industry & Technology Institute (KEITI) through Wetland Ecosystem Value Evaluation and Carbon Absorption Value Promotion Technology Development Project, funded by Korea Ministry of Environment (MOE) (RS-2022-KE002066), and Water Management Program for Drought, funded by the Korea Ministry of Climate, Energy and Environment (MCEE) (RS-2022-KE002032).