Contrasting roles of interception and transpiration in the hydrological cycle – Part 2: Moisture recycling

Author(s): van der Ent, R. J., L. Wang-Erlandsson, P. W. Keys, H. H. G. Savenije
In: Earth System Dynamics Discussions
Year: 2014
Type: Journal / article
Theme affiliation: Patterns of the Anthropocene
Link to centre authors: Wang Erlandsson, Lan
Full reference: van der Ent, R. J., L. Wang-Erlandsson, P. W. Keys, H. H. G. Savenije 2014. Contrasting roles of interception and transpiration in the hydrological cycle – Part 2: Moisture recycling. Earth System Dynamics Discussions, 5, 281-326

Summary

The contribution of land evaporation to local and remote precipitation (i.e., moisture recycling) is of significant importance to sustain water resources and ecosystems. But how important are different evaporation components in sustaining precipitation? This is the first paper to present moisture recycling metrics for partitioned evaporation. In the companion paper, Part 1, evaporation was partitioned into vegetation interception, floor interception, soil moisture evaporation and open water evaporation (constituting the direct, purely physical fluxes, largely dominated by interception), and transpiration (delayed, biophysical flux). Here, we track these components forward as well as backward in time. We also include age tracers to study the atmospheric residence times of these evaporation components.

As the main result we present a new image of the global hydrological cycle that includes quantification of partitioned evaporation and moisture recycling as well as the atmospheric residence times of all fluxes. We demonstrate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, direct evaporation (essentially interception) is found to have an atmospheric residence time of eight days, while transpiration typically resides nine days in the atmosphere. Interception recycling has a much shorter local length scale than transpiration recycling, thus interception generally precipitates closer to its evaporative source than transpiration, which is particularly pronounced outside the tropics.

We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells. On the other hand, transpiration remains active during dry spells and is transported over much larger distances downwind where it can act as a significant source of moisture. Thus, as various land-use types can differ considerably in their partitioning between interception and transpiration, our results stress that land-use changes (e.g., forest to cropland conversion) do not only affect the magnitude of moisture recycling, but could also influence the moisture recycling patterns and lead to a redistribution of water resources. As such, this research highlights that land-use changes can have complex effects on the atmospheric branch of the hydrological cycle.

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