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| Titel |
Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis |
| VerfasserIn |
B. A. Flowers, M. K. Dubey, C. Mazzoleni, E. A. Stone, J. J. Schauer, S.-W. Kim, S. C. Yoon |
| 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. 21 ; Nr. 10, no. 21 (2010-11-05), S.10387-10398 |
| Datensatznummer |
250008873
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| Publikation (Nr.) |
 copernicus.org/acp-10-10387-2010.pdf |
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| Zusammenfassung |
| Transport of aerosols in pollution plumes from the mainland Asian continent
was observed in situ at Jeju, South Korea during the Cheju Asian Brown
Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout
August and September 2008 using a 3-laser photoacoustic spectrometer
(PASS-3), chemical filter analysis, and size distributions. The PASS-3
directly measures the effects of morphology (e.g. coatings) on light
absorption that traditional filter-based instruments are unable to address.
Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various
Asian pollution plumes to Jeju accounted for 74% of the deployment days,
showing large variations in their measured chemical and optical properties.
Analysis of eight distinct episodes, spanning wide ranges of chemical
composition, optical properties, and source regions, reveals that episodes
with higher organic carbon (OC)/sulfate (SO42−) and nitrate
(NO3−)/SO42− composition ratios exhibit lower single scatter albedo
at shorter wavelengths (ω405). We infer complex refractive indices
(n–ik) as a function of wavelength for the high, intermediate, and low
OC/SO42− pollution episodes by using the observed particle size
distributions and the measured optical properties. The smallest mean particle
diameter corresponds to the high OC/SO42− aerosol episode. The
imaginary part of the refractive index (k) is greater for the high
OC/SO42− episode at all wavelengths. A distinct, sharp increase in k
at short wavelength implies enhanced light absorption by OC, which accounts
for 50% of the light absorption at 405 nm, in the high OC/SO42−
episode. Idealized analysis indicates increased absorption at 781 nm by
factors greater than 3 relative to denuded black carbon in the laboratory. We
hypothesize that coatings of black carbon cores are the mechanism of this
enhancement. This implies that climate warming and atmospheric heating rates
from black carbon particles can be significantly larger than have been
estimated previously. The results of this study demonstrate ways in which atmospheric
processing and mixing can amplify particle light absorption for carbonaceous
aerosol, significantly at short wavelength, underscoring the need to
understand and predict chemical composition effects on optical properties to
accurately estimate the climate radiative forcing by mixed carbonaceous
aerosols. |
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