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| Titel |
The analysis of size-segregated cloud condensation nuclei counter (CCNC) data and its implications for cloud droplet activation |
| VerfasserIn |
M. Paramonov, P. P. Aalto, A. Asmi, N. Prisle, V.-M. Kerminen, M. Kulmala  , T. Petäjä |
| 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 ; 13, no. 20 ; Nr. 13, no. 20 (2013-10-23), S.10285-10301 |
| Datensatznummer |
250085762
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| Publikation (Nr.) |
 copernicus.org/acp-13-10285-2013.pdf |
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| Zusammenfassung |
| Ambient aerosol, CCN (cloud condensation nuclei) and hygroscopic properties were measured with a
size-segregated CCNC (cloud condensation nuclei counter) in a boreal environment of southern Finland at the SMEAR
(Station for Measuring Ecosystem-Atmosphere Relations) II station. The instrumental setup operated at five levels of supersaturation
S covering a range from 0.1–1% and measured particles with a size
range of 20–300 nm; a total of 29 non-consecutive months of data are
presented. The median critical diameter Dc ranged from 150 nm at
S of 0.1% to 46 nm at S of 1.0%. The median aerosol
hygroscopicity parameter κ ranged from 0.41 at S of 0.1% to
0.14 at S of 1.0%, indicating that ambient aerosol in Hyytiälä
is less hygroscopic than the global continental or European continental
averages. It is, however, more hygroscopic than the ambient aerosol in an
Amazon rainforest, a European high Alpine site or a forested mountainous
site. A fairly low hygroscopicity in Hyytiälä is likely a result of a
large organic fraction present in the aerosol mass comparative to other
locations within Europe. A considerable difference in particle hygroscopicity
was found between particles smaller and larger than ~100 nm in
diameter, possibly pointing out to the effect of cloud processing increasing
κ of particles > 100 nm in diameter. The hygroscopicity of the
smaller, ~50 nm particles did not change seasonally, whereas
particles with a diameter of ~150 nm showed a decreased hygroscopicity
in the summer, likely resulting from the increased VOC emissions of the
surrounding boreal forest and secondary organic aerosol (SOA) formation. For
the most part, no diurnal patterns of aerosol hygroscopic properties were
found. Exceptions to this were the weak diurnal patterns of small,
~50 nm particles in the spring and summer, when a peak in
hygroscopicity around noon was observed. No difference in CCN activation and
hygroscopic properties was found on days with or without atmospheric new
particle formation. During all seasons, except summer, a CCN-inactive
fraction was found to be present, rendering the aerosol of 75–300 nm in
diameter as internally mixed in the summer and not internally mixed for the
rest of the year. |
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