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| Titel |
Intercomparison of aerosol climatologies for use in a regional climate model over Europe |
| VerfasserIn |
E. M. Zubler, U. Lohmann, D. Lüthi, C. Schär |
| 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 |
250060952
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| Zusammenfassung |
| Many regional climate models (RCM) and numerical weather prediction (NWP) models use
out-dated aerosol data sets to calculate the direct aerosol radiative effect. In this study, three
multi-year simulations with the regional climate model COSMO-CLM using different aerosol
climatologies and a simulation with monthly mean aerosol optical properties, stemming from
a COSMO-CLM simulation with coupled aerosol microphysics and transport, are
evaluated.
The climatologies of Tegen et al. (1997), the AEROCOM-climatology for present-day
conditions, and the monthly mean optical properties from Zubler et al. (2011), that
show realistic patterns of aerosol optical depth (AOD), lead to an increase of annual
mean downward surface shortwave radiation (SSR) of 35Â WÂ m-2 (20%) in the
Mediterranean region in comparison with the climatology of Tanré et al. (1984)
(TAN84). The former is known to strongly overestimate AOD over Europe owing to an
unrealistic representation of desert dust. The associated bias in SSR exceeds the
observed variations of the recent decades by up to a factor 5. Despite an annual mean
temperature increase of more than 0.5Â K above Southern European land surfaces
owing to the enhanced SSR, the newer climatologies yield colder temperatures in
the mid-troposphere because of a reduction of the shortwave absorption by desert
dust.
Consequently, the reduced tropospheric heating, in combination with the surface
warming, destabilizes the atmosphere relative to the simulation with TAN84, amplifying
cloud formation and precipitation in these simulations. In the Northern part of Europe, the
cloud fraction increases by roughly 2.5% in the annual mean. Over Scandinavia,
this effect is even stronger than the increase in SSR due to reduced AOD, such
that colder temperatures result in comparison with TAN84. Locally, the annual
mean precipitation increases by up to 15%. It is thus recommended that the RCM
community uses updated aerosol information for radiative transfer calculations. |
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