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| Titel |
Estimated variability of below-cloud aerosol removal by rainfall for observed aerosol size distributions |
| VerfasserIn |
C. Andronache |
| 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 ; 3, no. 1 ; Nr. 3, no. 1 (2003-02-11), S.131-143 |
| Datensatznummer |
250000715
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| Publikation (Nr.) |
 copernicus.org/acp-3-131-2003.pdf |
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| Zusammenfassung |
| Below-cloud scavenging (BCS) coefficients of aerosols by rainfall are estimated for
reported aerosol size distributions measured during field experiments in various
environments. The method employed is based on explicit calculations of the efficiency of
collision between a raindrop and aerosol particles. Such BCS coefficients can be
used in numerical models that describe: 1) the detailed evolution of aerosol size
distribution and, 2) the evolution of total aerosol mass concentration. The effects
of raindrop size distribution and aerosol size distribution variability on
BCS coefficients are illustrated using observed data. Results show that BCS coefficient
increases with rainfall rate and has a significant dependence on aerosol size distribution
parameters. Thus, BCS is important for very small particles (with diameters less than
0.01 $\mu$m) and for coarse particles (with diameters larger than 2 µm). For rainfall rate
R ~ 1 mm hr-1, the 0.5-folding time of these particles is of the order of one hour. It is shown
that BCS is negligible for aerosol particles in the range [0.1-1] µm if compared with in-cloud
scavenging rates for low and moderate rainfall rates ( R ~ 0.1-10 mm hr-1). The
results indicate that a boundary layer aerosol size distribution with coarse mode is
drastically affected very shortly after rain starts (in a fraction of one hour) and
consequently, the below-cloud aerosol size distribution becomes dominated by particles
in the accumulation mode. |
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