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| Titel |
Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China |
| VerfasserIn |
L. Zhang, J. Y. Sun, X. J. Shen, Y. M. Zhang, H. Che, Q. L. Ma, Y. W. Zhang, X. Y. Zhang, J. A. Ogren |
| 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 ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-28), S.8439-8454 |
| Datensatznummer |
250119935
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| Publikation (Nr.) |
 copernicus.org/acp-15-8439-2015.pdf |
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| Zusammenfassung |
| Scattering of solar radiation by aerosol particles is highly dependent on
relative humidity (RH) as hygroscopic particles take up water with
increasing RH. To achieve a better understanding of the effect of aerosol
hygroscopic growth on light scattering properties and radiative forcing, the
aerosol scattering coefficients at RH in the range of 40 to ~ 90 % were measured using a humidified nephelometer system in the Yangtze
River Delta of China in March 2013. In addition, the aerosol size
distribution and chemical composition were measured. During the observation
period, the mean and standard deviation (SD) of enhancement factors at
RH = 85 % for the scattering coefficient (f(85 %)), backscattering
coefficient (fb(85 %)), and hemispheric backscatter fraction
(fβ(85 %)) were 1.58 ± 0.12, 1.25 ± 0.07, and
0.79 ± 0.04, respectively, i.e., aerosol scattering coefficient and
backscattering coefficient increased by 58 and 25 % as the RH increased
from 40 to 85 %. Concurrently, the aerosol hemispheric backscatter fraction
decreased by 21 %. The relative amount of organic matter (OM) or
inorganics in PM1 was found to be a main factor determining the
magnitude of f(RH). The highest values of f(RH) corresponded to the aerosols
with a small fraction of OM, and vice versa. The relative amount of
NO3− in fine particles was strongly
correlated with f(85 %), which suggests that
NO3− played a vital role in aerosol
hygroscopic growth during this study. The mass fraction of nitrate also had
a close relationship to the curvature of the humidograms; higher mass fractions
of nitrate were associated with humidograms that had the least curvature.
Aerosol hygroscopic growth caused a 47 % increase in the calculated
aerosol direct radiative forcing at 85 % RH, compared to the forcing at
40 % RH. |
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