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| Titel |
Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective |
| VerfasserIn |
A. Alessandri, P. G. Fogli, M. Vichi, N. Zeng |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-4979
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| Digitales Dokument |
URL |
| Erschienen |
In: Earth System Dynamics ; 3, no. 2 ; Nr. 3, no. 2 (2012-11-22), S.199-212 |
| Datensatznummer |
250001011
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| Publikation (Nr.) |
 copernicus.org/esd-3-199-2012.pdf |
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| Zusammenfassung |
Future climate scenarios experiencing global warming are expected to
strengthen the hydrological cycle during the 21st century (21C). We analyze
the strengthening of the global-scale increase in precipitation from the
perspective of changes in whole atmospheric water and energy balances. By
combining energy and water equations for the whole atmosphere, we obtain
constraints for the changes in surface fluxes and partitioning at the surface
between sensible and latent components. We investigate the differences in the
strengthening of the hydrological cycle in two centennial simulations
performed with an Earth system model forced with specified atmospheric
concentration pathways. Alongside the Special Report on Emissions Scenario
(SRES) A1B, which is a medium-high non-mitigation scenario, we consider a new
aggressive-mitigation scenario (E1) with reduced fossil fuel use for energy
production aimed at stabilizing global warming below 2 K.
Our results show that the mitigation scenario effectively constrains the
global warming with a stabilization below 2 K with respect to the 1950–2000
historical period. On the other hand, the E1 precipitation does not follow
the temperature field toward a stabilization path but continues to increase
over the mitigation period. Quite unexpectedly, the mitigation scenario is
shown to strengthen the hydrological cycle even more than SRES A1B till
around 2070.
We show that this is mostly a consequence of the larger increase in the
negative radiative imbalance of atmosphere in E1 compared to A1B. This
appears to be primarily related to decreased sulfate aerosol concentration in
E1, which considerably reduces atmospheric absorption of solar radiation
compared to A1B.
The last decades of the 21C show a marked increase in global precipitation in
A1B compared to E1, despite the fact that the two scenarios display almost
the same overall increase of radiative imbalance with respect to the
20th century. Our results show that radiative cooling is weakly
effective in A1B throughout the 21C. Two distinct mechanisms characterize the
diverse strengthening of the hydrological cycle in the middle and end-
21C. It is only through a very large perturbation of surface fluxes that A1B
achieves a larger increase in global precipitation in the last decades of the
21C. Our energy/water budget analysis shows that this behavior is ultimately
due to a bifurcation in the Bowen ratio change between the two scenarios.
This work warns that mitigation policies that promote aerosol abatement, may
lead to an unexpected stronger intensification of the hydrological cycle and
associated changes that may last for decades after global warming is
effectively mitigated. On the other hand, it is also suggested that
predictable components of the radiative forcing by aerosols may have the
potential to effectively contribute to the decadal-scale predictability of
changes in the hydrological strength. |
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