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| Titel |
Hygroscopic properties of the ambient aerosol in southern Sweden – a two year study |
| VerfasserIn |
E. O. Fors, E. Swietlicki, B. Svenningsson, A. Kristensson, G. P. Frank, M. Sporre |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-16), S.8343-8361 |
| Datensatznummer |
250010008
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| Publikation (Nr.) |
 copernicus.org/acp-11-8343-2011.pdf |
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| Zusammenfassung |
| The hygroscopic growth of the atmospheric aerosol is a critical parameter
for quantifying the anthropogenic radiative forcing. Until now, there has
been a lack of long term measurements due to limitations in instrumental
techniques. In this work, for the first time the seasonal variation of the
hygroscopic properties of a continental background aerosol has been
described, based on more than two years of continuous measurements. In
addition to this, the diurnal variation of the hygroscopic growth has been
investigated, as well as the seasonal variation in CCN concentration. These
physical properties of the aerosol have been measured with a Hygroscopic
Tandem Differential Mobility Analyzer (H-TDMA), a Differential Mobility
Particle Sizer (DMPS), and a Cloud Condensation Nuclei Counter (CCNC). The
results show that smaller particles are generally less hygroscopic than
larger ones, and that there is a clear difference in the hygroscopic
properties between the Aitken and the accumulation mode. A seasonal cycle
was found for all particle sizes. In general, the average hygroscopic growth
is lower during wintertime, due to an increase in the relative abundance of
less hygroscopic or barely hygroscopic particles. Monthly averages showed
that the hygroscopic growth factors of the two dominating hygroscopic modes
(one barely hygroscopic and one more hygroscopic) were relatively stable.
The hygroscopic growth additionally showed a diurnal cycle, with higher
growth factors during day time. CCN predictions based on H-TDMA data
underpredicted the activated CCN number concentration with 7 % for a 1 %
water supersaturation ratio. The underprediction increases with decreasing
s, most likely due to a combination of measurement and modeling
uncertainties. It was found that although the aerosol is often externally
mixed, recalculating to an internal mixture with respect to hygroscopicity
did not change the CCN concentration as a function of supersaturation
significantly. |
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