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| Titel |
On aerosol hygroscopicity, cloud condensation nuclei (CCN) spectra and critical supersaturation measured at two remote islands of Korea between 2006 and 2009 |
| VerfasserIn |
J. H. Kim, S. S. Yum, S. Shim, S.-C. Yoon, J. G. Hudson, J. Park, S.-J. Lee |
| 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. 24 ; Nr. 11, no. 24 (2011-12-15), S.12627-12645 |
| Datensatznummer |
250010269
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| Publikation (Nr.) |
 copernicus.org/acp-11-12627-2011.pdf |
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| Zusammenfassung |
Aerosol size distribution, total concentration (i.e. condensation nuclei
(CN) concentration, NCN), cloud condensation nuclei (CCN) concentration
(NCCN), hygroscopicity at ~90% relative humidity (RH) were
measured at a background monitoring site at Gosan, Jeju Island, south of the
Korean Peninsula in August 2006, April to May 2007 and August to October
2008. Similar measurements took place in August 2009 at another background
site (Baengnyeongdo Comprehensive Monitoring Observatory, BCMO) on the
island of Baengnyeongdo, off the west coast of the Korean Peninsula. Both
islands were found to be influenced by continental sources regardless of
season and year. Average values for all of the measured NCCN at 0.2,
0.6 and 1.0% supersaturations (S), NCN, and geometric mean diameter
(Dg) from both islands were in the range of 1043–3051 cm−3,
2076–4360 cm−3, 2713–4694 cm−3, 3890–5117 cm−3 and
81–98 nm, respectively. Although the differences in Dg and NCN were
small between Gosan and BCMO, NCCN at various S was much higher at the
latter, which is closer to China.
Most of the aerosols were internally mixed and no notable differences in
hygroscopicity were found between the days of strong pollution influence and
the non-pollution days for both islands. During the 2008 and 2009 campaigns,
critical supersaturation for CCN nucleation (Sc) for selected particle
sizes was measured. Particles of 100 nm diameters had mean Sc of
0.19 ± 0.02% during 2008 and those of 81 and 110 nm diameters had mean
Sc of 0.26 ± 0.07% and 0.17 ± 0.04%, respectively, during
2009. The values of the hygroscopicity parameter (κ), estimated from
measured Sc, were mostly higher than the κ values obtained from
the measured hygroscopic growth at ~90% RH.
For the 2008 campaign, NCCN at 0.2, 0.6 and 1.0% S were predicted
based on measured dry particle size distributions and various ways of
representing particle hygroscopicity. The best closure was obtained when
temporally varying and size-resolved hygroscopicity information from the
HTDMA was used, for which the average relative deviations from the measured
values were 28 ± 20% for 0.2% S (mostly under-prediction), 25 ± 52% for 0.6% (balanced between over- and under-prediction) and 19 ± 15% for 1.0% S (balanced). Prescribing a constant hygroscopicity
parameter suggested in the literature (κ = 0.3) for all sizes and
times resulted in average relative deviations of 28–41% where
over-prediction was dominant. When constant hygroscopicity was assumed, the
relative deviation tended to increase with decreasing NCCN, which was
accompanied by an increase of the sub-100 nm fraction. These results suggest
that hygroscopicity information for particles of diameters smaller than 100 nm
is crucial for more accurate predictions of NCCN. For confirmation
when κ = 0.17, the average κ for sub-100 nm particles in this
study, was applied for sub-100 nm and κ = 0.3 for all other sizes,
the CCN closure became significantly better than that with κ = 0.3 for
all sizes. |
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