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| Titel |
New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland) |
| VerfasserIn |
J. Boulon, K. Sellegri, H. Venzac, D. Picard, E. Weingärtner, G. Wehrle, M. Collaud Coen, R. Bütikofer, E. Flückiger, U. Baltensperger, P. Laj |
| 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 ; 10, no. 19 ; Nr. 10, no. 19 (2010-10-05), S.9333-9349 |
| Datensatznummer |
250008804
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| Publikation (Nr.) |
 copernicus.org/acp-10-9333-2010.pdf |
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| Zusammenfassung |
| We investigate the formation and growth of charged aerosols clusters at
Jungfraujoch, in the Swiss Alps (3580 m a.s.l.), the highest altitude
site of the European EUCAARI project intensive campaign. Charged particles
and clusters (0.5–1.8 nm) were measured from April 2008 to April 2009 and
allowed the detection of nucleation events in this very specific environment
(presence of free tropospheric air and clouds). We found that the naturally
charged aerosol concentrations, which are dominated by the cluster size class,
shows a strong diurnal pattern likely linked to valley breezes
transporting surface layer ion precursors, presumably radon. Cosmic rays were
found not to be the major ion source at the measurement site. However, at night,
when air masses are more representative of free tropospheric conditions, we found
that the cluster concentrations are still high. The charged aerosol size distribution
and concentration are strongly influenced by the presence of clouds at the
station. Clouds should be taken into account when deriving high altitude nucleation
statistics. New particle formation occurs on average 17.5% of the measurement period and shows a weak
seasonality with a minimum of frequency during winter, but this seasonality
is enhanced when the data set is screened for periods when the atmospheric
station is out of clouds. The role of ions in the nucleation process was
investigated and we found that the ion-mediated nucleation explains 22.3%
of the particle formation. The NPF events frequency is correlated with UV
radiation but not with calculated H2SO4 concentrations,
suggesting that other compounds such as organic vapors are involved in the
nucleation and subsequently growth process. In fact, NPF events frequency
also surprisingly increases with the condensational sink (CS), suggesting
that at Jungfraujoch, the presence of condensing vapours probably coupled
with high CS are driving the occurrence of NPF events. A strong link to the
air mass path was also pointed out and events were observed to be frequently
occurring in Eastern European air masses, which present the highest
condensational sink. In these air masses, pre-existing cluster concentrations
are more than three time larger than in other air masses during event days,
and no new clusters formation is observed, contrarily to what is happening in
other air mass types. |
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