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| Titel |
Intercomparison of aerosol microphysics modules in the framework of the ECHAM5 climate model |
| VerfasserIn |
R. Hommel, H. Kokkola, J. Kazil, U. Niemeier, AI Partanen, J. Feichter, C. Timmreck |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023267
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| Zusammenfassung |
| Aerosols in the atmosphere are an elementary constituent of the atmospheric composition and
affect the global climate through a variety of physical and chemical interactions in the
troposphere and stratosphere. Large volcanic eruptions alter the Earth’s radiative balance and
interfere with the catalytic cycles of ozone depletion mainly by the formation of micrometer
size aerosol particles above the tropopause.
Recent experimental and numerical investigations of process oriented aerosol-climate
interactions revealed that appropriate climate effects can only be modeled when informations
about the aerosol size and number spectra are provided. Nevertheless in the majority of
climate models volcanic perturbations of the stratosphere are either prescribed based on the
aerosol parameters of interested (surface area, optical depth) or the aerosol microphysics is
considered explicitly but with a heavily reduced number of degrees of freedom.
This yields e.g. to underestimations of surface temperature effects in the fade of an
eruption.
To overcome that weakness, we tested three aerosol modules currently available in the
framework of the climate model ECHAM5 in environmental conditions assumed to be
representative in the stratosphere after the injection of SO2 from modest to large
volcanic eruptions. The study focuses on the evolution of liquid H2SO4/H2O
aerosol.
The modal modal M7, currently the default aerosol scheme in ECHAM5, is compared
with two sectional aerosol schemes: the moving centre sectional aerosol scheme SALSA,
and the fixed sectional scheme SAM2. Since direct measurements of particle size
informations during the initial stage of a volcanic injection in the stratosphere are not
available, the detailed sectional aerosol model MAIA is used as a reference in this
study.
It is shown that all modules are able to represent a "typical" stratospheric background
aerosol distribution when the particles are formed via the oxidation pathway of
SO2. However, the modules differ strongly and their setup have to be changed to
be applied in global model simulations capturing respective volcanic episodes. |
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