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| Titel |
Microphysical processing of aerosol particles in orographic clouds |
| VerfasserIn |
S. Pousse-Nottelmann, E. M. Zubler, U. Lohmann |
| 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 ; 15, no. 16 ; Nr. 15, no. 16 (2015-08-20), S.9217-9236 |
| Datensatznummer |
250119977
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| Publikation (Nr.) |
 copernicus.org/acp-15-9217-2015.pdf |
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| Zusammenfassung |
An explicit and detailed treatment of cloud-borne particles allowing for the consideration of
aerosol cycling in clouds has been implemented into COSMO-Model, the regional weather forecast and climate model of the Consortium for Small-scale Modeling (COSMO). The effects of aerosol scavenging, cloud microphysical processing and regeneration upon
cloud evaporation on the aerosol population and on subsequent cloud formation are investigated. For
this, two-dimensional idealized simulations of moist flow over two bell-shaped mountains were
carried out varying the treatment of aerosol scavenging and regeneration processes for a warm-phase
and a mixed-phase orographic cloud.
The results allowed us to identify different aerosol cycling mechanisms. In the simulated non-precipitating
warm-phase cloud, aerosol mass is incorporated into cloud droplets by activation scavenging and
released back to the atmosphere upon cloud
droplet evaporation. In the mixed-phase cloud, a first cycle comprises cloud droplet
activation and evaporation via the Wegener–Bergeron–Findeisen (WBF) process. A second cycle includes
below-cloud scavenging by precipitating snow particles and snow sublimation and is connected to
the first cycle via the riming process which transfers aerosol mass from cloud droplets to snowflakes. In the simulated mixed-phase cloud, only a negligible part of the total aerosol mass is
incorporated into ice crystals. Sedimenting snowflakes reaching the surface remove
aerosol mass from the atmosphere. The results show that aerosol processing and regeneration lead
to a vertical redistribution of aerosol mass and number. Thereby, the processes impact the total aerosol number and mass and additionally alter the shape of the aerosol size distributions by
enhancing the internally mixed/soluble Aitken and accumulation mode and generating coarse-mode particles.
Concerning subsequent cloud formation at the second mountain, accounting for
aerosol processing and regeneration increases the cloud droplet number concentration with possible
implications for the ice crystal number concentration. |
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