Revisiting global oceanic and terrestrial moisture sources based on state-of-the-art Lagrangian transport simulations

Understanding atmospheric moisture sources and their transport pathways is essential for advancing our knowledge of hydrological processes, regional precipitation patterns, and climate variability. In this study, we analyze continental and oceanic moisture sources with a focus on climatological patterns and long-term trends. To revisit our understanding of global moisture sources, we leverage a new global, open-source dataset spanning 45 years (1979–2024), derived from Lagrangian transport modeling with FLEXPART (Bakels et al, 2024). It contains 3-hourly information on the position of the air parcels — which are distributed globally according to density — as well as different associated state variables such as temperature or specific humidity. 

The outputs from the Lagrangian model are fed to HAMSTER, a tool for source attribution that is constrained by observational data of both precipitation and evaporation (Keune et al., 2022). Notably, we analyze the moisture sources for each continent separately in addition to the sources for the global land area as a whole, which enables us to: (1) assess intra-continental precipitation and evaporation recycling ratios, (2) investigate the inter-continental transport of moisture, and (3) analyze the role of different ocean basins in providing moisture to specific terrestrial regions. Moreover, the dataset’s longer record and its higher spatial and temporal resolution compared to their predecessors allow for an up-to-date investigation of the change in moisture source contributions over the past four decades. This includes exploring the impact of climate change and land use alterations on the hydrological cycle and how these changes affect the balance between oceanic and terrestrial moisture sources per continent. Overall, this study refines our understanding of atmospheric moisture transport dynamics in a changing climate, highlighting ongoing shifts in our global hydrological cycle.  

 

References

Bakels, L., Tatsii, D., Tipka, A., Thompson, R., Dütsch, M., Blaschek, M., Seibert, P., Baier, K., Bucci, S., Cassiani, M., Eckhardt, S., Groot Zwaaftink, C., Henne, S., Kaufmann, P., Lechner, V., Maurer, C., Mulder, M. D., Pisso, I., Plach, A., Subramanian, R., Vojta, M., and Stohl, A.: FLEXPART version 11: improved accuracy, efficiency, and flexibility, Geosci. Model Dev., 17, 7595–7627, https://doi.org/10.5194/gmd-17-7595-2024, 2024. 

Keune, J., Schumacher, D. L., and Miralles, D. G.: A unified framework to estimate the origins of atmospheric moisture and heat using Lagrangian models, Geosci. Model Dev., 15, 1875–1898, https://doi.org/10.5194/gmd-15-1875-2022, 2022.