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| Titel |
Spatial and temporal variability of soil moisture–temperature coupling in current and future climate |
| VerfasserIn |
Clemens Schwingshackl, Martin Hirschi, Sonia Isabelle Seneviratne |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140350
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| Publikation (Nr.) |
 EGU/EGU2017-3724.pdf |
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| Zusammenfassung |
| While climate models generally agree on a future global mean temperature increase, the exact
rate of change is still uncertain. The uncertainty is even higher for regional temperature trends
that can deviate substantially from the projected global temperature increase. Several studies
tried to constrain these regional temperature projections. They found that over land areas soil
moisture is an important factor that influences the regional response. Due to the limited
knowledge of the influence of soil moisture on atmospheric conditions on global scale the
constraint remains still weak, though.
Here, we use a framework that is based on the dependence of evaporative fraction
(i.e. the fraction of net radiation that goes into latent heat flux) on soil moisture to
distinguish between different soil moisture regimes (Seneviratne et al., 2010). It allows
to estimate the influence of soil moisture on near-surface air temperature in the
current climate and in future projections. While in the wet soil moisture regime,
atmospheric conditions and related land surface fluxes can be considered as mostly
driven by available energy, in the transitional regime - where evaporative fraction
and soil moisture are essentially linearly coupled - soil moisture has an impact
on turbulent heat fluxes, air humidity and temperature: Decreasing soil moisture
and concomitant decreasing evaporative fraction cause increasing sensible heat
flux, which might further lead to higher surface air temperatures. We investigate
the strength of the single couplings (soil moisture → latent heat flux → sensible
heat flux → air temperature) in order to quantify the influence of soil moisture on
surface air temperature in the transitional regime. Moreover, we take into account that
the coupling strength can change in the course of the year due to seasonal climate
variations.
The relations between soil moisture, evaporative fraction and near-surface air temperature
in re-analysis and observation-based data products (Schwingshackl et al., in review) are
compared to CMIP5 model outputs for current climate conditions. This allows to estimate if
the single models correctly reproduce the observed relations. Moreover, the analysis is
conducted for future climate projections to identify regions where shifts in soil
moisture regimes occur. Eventually, the impact of these shifts on near-surface air
temperature is analyzed to evaluate the influence of soil moisture on future temperature
changes.
References:
Seneviratne, S. I., T. Corti, E. L. Davin, M. Hirschi, E. B. Jaeger, I. Lehner, B. Orlowsky, and
A. J. Teuling, 2010: Investigating soil moisture–climate interactions in a changing climate: A
review. Earth-Science Reviews, 99 (3), 125–161, doi:10.1016/j.earscirev.2010.02.004.
Schwingshackl, C., M. Hirschi, and S. I. Seneviratne: Quantifying spatio–temporal
variations of soil moisture control on surface energy balance and near-surface air
temperature. Journal of Climate (in review) |
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