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| Titel |
The contribution of fungal spores and bacteria to regional and global aerosol number and ice nucleation immersion freezing rates |
| VerfasserIn |
D. V. Spracklen, C. L. Heald |
| 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 ; 14, no. 17 ; Nr. 14, no. 17 (2014-09-02), S.9051-9059 |
| Datensatznummer |
250118999
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| Publikation (Nr.) |
 copernicus.org/acp-14-9051-2014.pdf |
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| Zusammenfassung |
| Primary biological aerosol particles (PBAPs) may play an important role in
aerosol–climate interactions, in particular by affecting ice formation in
mixed phase clouds. However, the role of PBAPs is poorly understood because
the sources and distribution of PBAPs in the atmosphere are not well
quantified. Here we include emissions of fungal spores and bacteria in a
global aerosol microphysics model and explore their contribution to
concentrations of supermicron particle number, cloud condensation nuclei
(CCN) and immersion freezing rates. Simulated surface annual mean
concentrations of fungal spores are ~ 2.5 × 104 m−3 over continental midlatitudes and 1 × 105 m−3
over tropical forests. Simulated surface concentrations of bacteria are
2.5 × 104 m−3 over most continental regions and
5 × 104 m−3 over grasslands of central Asia and North
America. These simulated surface number concentrations of fungal spores and
bacteria are broadly in agreement with the limited available observations.
We find that fungal spores and bacteria contribute 8 and 5%
respectively to simulated continental surface mean supermicron number
concentrations, but have very limited impact on CCN concentrations, altering
regional concentrations by less than 1%. In agreement with previous
global modelling studies, we find that fungal spores and bacteria contribute
very little (3 × 10−3%, even when we assume upper limits for
ice nucleation activity) to global average immersion freezing ice nucleation
rates, which are dominated by soot and dust. However, at lower altitudes
(400 to 600 hPa), where warmer temperatures mean that soot and dust may
not nucleate ice, we find that PBAP controls the immersion freezing ice
nucleation rate. This demonstrates that PBAPs can be of regional importance
for IN formation, in agreement with case study observations. |
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