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| Titel |
Simplified aerosol modeling for variational data assimilation |
| VerfasserIn |
N. Huneeus, O. Boucher, F. Chevallier |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 2, no. 2 ; Nr. 2, no. 2 (2009-11-16), S.213-229 |
| Datensatznummer |
250000547
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| Publikation (Nr.) |
 copernicus.org/gmd-2-213-2009.pdf |
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| Zusammenfassung |
We have developed a simplified aerosol model together with its tangent linear
and adjoint versions for the ultimate aim of optimizing global aerosol and
aerosol precursor emission using variational data assimilation. The model was
derived from the general circulation model LMDz; it groups together the
24 aerosol species simulated in LMDz into 4 species, namely gaseous
precursors, fine mode aerosols, coarse mode desert dust and coarse mode sea
salt. The emissions have been kept as in the original model. Modifications,
however, were introduced in the computation of aerosol optical depth and in
the processes of sedimentation, dry and wet deposition and sulphur chemistry
to ensure consistency with the new set of species and their composition.
The simplified model successfully manages to reproduce the main features of
the aerosol distribution in LMDz. The largest differences in aerosol load are
observed for fine mode aerosols and gaseous precursors. Differences between
the original and simplified models are mainly associated to the new
deposition and sedimentation velocities consistent with the definition of
species in the simplified model and the simplification of the sulphur
chemistry. Furthermore, simulated aerosol optical depth remains within the
variability of monthly AERONET observations for all aerosol types and all
sites throughout most of the year. Largest differences are observed over
sites with strong desert dust influence. In terms of the daily aerosol
variability, the model is less able to reproduce the observed variability
from the AERONET data with larger discrepancies in stations affected by
industrial aerosols. The simplified model however, closely follows the daily
simulation from LMDz.
Sensitivity analyses with the tangent linear version show that the simplified
sulphur chemistry is the dominant process responsible for the strong
non-linearity of the model. |
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