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| Titel |
Simulation of dimming and brightening in Europe from 1958 to 2001 using a regional climate model |
| VerfasserIn |
E. M. Zubler, U. Lohmann, D. Lüthi, C. Schär, M. Wild |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060959
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| Zusammenfassung |
| This study applies a regional climate model with coupled aerosol microphysics and transport
in order to simulate dimming and, in particular, brightening in Europe from 1958 to
2001. Two simulations are performed, one with transient emissions and another
with climatological mean emissions over the same period. Both simulations are
driven at the lateral boundaries by the ERA-40 reanalysis and by large-scale aerosol
concentrations stemming from a global simulation with the general circulation model
ECHAM5-HAM. We find distinct patterns of dimming and brightening in the aerosol
optical depth and thus clear-sky downward surface shortwave radiation (SSR) in
all analyzed subregions. The strongest brightening between 1973 and 1998 under
clear-sky conditions is found in Mid-Europe (+3.4Â WÂ m-2 per decade, in line with
observations).
However, the simulated all-sky SSR is dominated by the surface shortwave cloud
radiative forcing (CRF). The correlation coefficient R between five-year moving
averages of the CRF and all-sky SSR equals 0.87 for entire Europe. Both model
simulations as well as the driving ERA-40 reanalysis show a similar evolution of cloud
fraction and thus all-sky SSR. On the one hand, this is not surprising as the RCM
inherits the circulation pattern at the lateral boundaries from the reanalysis. On the
other hand, this supports the finding that transient aerosol emissions only have
a minor impact on all-sky SSR as compared to clouds. For most subregions, the
modeled differences in all-sky SSR due to transient versus climatological emissions are
insignificant in comparison with estimates of the model’s internal variability. However, an
evaluation of all-sky SSR trends with station data all over Europe indicates that
particularly in Eastern Europe the model tends to underestimate the role of aerosols. |
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