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| Titel |
Regional scale effects of the aerosol cloud interaction simulated with an online coupled comprehensive chemistry model |
| VerfasserIn |
M. Bangert, C. Kottmeier, B. Vogel, H. Vogel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 9 ; Nr. 11, no. 9 (2011-05-11), S.4411-4423 |
| Datensatznummer |
250009711
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| Publikation (Nr.) |
 copernicus.org/acp-11-4411-2011.pdf |
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| Zusammenfassung |
We have extended the coupled mesoscale atmosphere and
chemistry model COSMO-ART to account for the transformation of
aerosol particles into cloud condensation nuclei and to
quantify their interaction with warm cloud microphysics on the
regional scale. The new model system aims to fill the gap
between cloud resolving models and global scale models. It
represents the very complex microscale aerosol and cloud
physics as detailed as possible, whereas the continental
domain size and efficient codes will allow for both studying
weather and regional climate. The model system is applied in
a first extended case study for Europe for a cloudy five day
period in August 2005.
The model results show that the mean cloud droplet number
concentration of clouds is correlated with the structure of
the terrain, and we present a terrain slope parameter TS to
classify this dependency. We propose to use this relationship
to parameterize the probability density function, PDF, of subgrid-scale cloud updraft
velocity in the activation parameterizations of climate
models.
The simulations show that the presence of cloud condensation nuclei (CCN) and clouds are
closely related spatially. We find high aerosol and CCN number
concentrations in the vicinity of clouds at high
altitudes. The nucleation of secondary particles is enhanced
above the clouds. This is caused by an efficient formation of
gaseous aerosol precursors above the cloud due to more
available radiation, transport of gases in clean air above the
cloud, and humid conditions. Therefore the treatment of
complex photochemistry is crucial in atmospheric models to
simulate the distribution of CCN.
The mean cloud droplet number concentration and droplet
diameter showed a close link to the change in the aerosol. To
quantify the net impact of an aerosol change on the
precipitation we calculated the precipitation susceptibility
β for the whole model domain over a period of two days
with an hourly resolution. The distribution function of
β is slightly skewed to positive values and has a mean
of 0.23. Clouds with a liquid water path LWP of approximately
0.85 kg m−2 are on average most susceptible to aerosol
changes in our simulations with an absolute value of β
of 1. The average β for LWP between 0.5 kg m−2
and 1 kg m−2 is approximately 0.4. |
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