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| Titel |
Variation of the radiative properties during black carbon aging: theoretical and experimental intercomparison |
| VerfasserIn |
C. He, K.-N. Liou, Y. Takano, R. Zhang, M. Levy Zamora, P. Yang, Q. Li, L. R. Leung |
| 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. 20 ; Nr. 15, no. 20 (2015-10-28), S.11967-11980 |
| Datensatznummer |
250120126
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| Publikation (Nr.) |
 copernicus.org/acp-15-11967-2015.pdf |
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| Zusammenfassung |
| A theoretical black carbon (BC) aging model is developed to account for
three typical evolution stages, namely, freshly emitted aggregates, BC coated
by soluble material, and BC particles undergoing further hygroscopic
growth. The geometric-optics surface-wave (GOS) approach is employed to
compute the BC single-scattering properties at each aging stage, which are
subsequently compared with laboratory measurements. Theoretical calculations
are consistent with measurements in extinction and absorption cross sections
for fresh BC aggregates with different BC sizes (i.e., mobility diameters of
155, 245, and 320 nm), with differences of ≤ 25 %. The measured
optical cross sections for BC coated by sulfuric acid and for that
undergoing further hygroscopic growth are generally captured (differences
< 30 %) by theoretical calculations using a concentric core-shell
structure, with an overestimate in extinction and absorption of the smallest
BC size and an underestimate in scattering of the largest BC size. We find
that the absorption and scattering cross sections of fresh BC aggregates
vary by 20–40 and 50–65 %, respectively, due to the use of upper (1.95–0.79i)
and lower (1.75–0.63i) bounds of BC refractive index, while the
variations are < 20 % in absorption and < 50 % in
scattering in the case of coated BC particles. Sensitivity analyses of the
BC morphology show that the optical properties of fresh BC aggregates are
more sensitive to fractal dimension than primary spherule size. The
absorption and scattering cross sections of coated BC particles vary by more
than a factor of 2 due to different coating structures. We find an
increase of 20–250 % in absorption and a factor of 3–15 in scattering
during aging, significantly depending on coating morphology and aging
stages. This study suggests that an accurate estimate of BC radiative
effects requires the incorporation of a dynamic BC aging process that
accounts for realistic coating structures in climate models. |
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