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.
Research news | 2018-08-14
New index reveals how climate risks are reinforced by global connectivity, leaving no country shielded from impact
General news | 2018-08-14
Event, Tuesday 11 September 2018 in partnership with ICF and the UN Climate Resilience Initiative A2R. A Global Climate Action Summit affiliate event
Research news | 2018-08-13
New analysis reveals connections between tax havens and resource degradation in both the Amazon rainforest and global fisheries
Research news | 2018-08-06
Keeping global warming to within 1.5-2°C may be more difficult than previously assessed
Research news | 2018-07-10
The World in 2050 initiative launches new report outlining synergies and benefits that render the goals achievable
Research news | 2018-06-27
Overfishing, fractured international relationships and political conflicts loom as fish migrate more unpredictably because of climate change. Here is how to deal with it