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| Titel |
A contribution of black and brown carbon to the aerosol light absorption |
| VerfasserIn |
Sang-Woo Kim, Chaeyoon Cho, Duseong Jo, Rokjin Park |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250142510
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| Publikation (Nr.) |
 EGU/EGU2017-6143.pdf |
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| Zusammenfassung |
| Black carbon (BC) is functionally defined as the absorbing component of atmospheric total
carbonaceous aerosols and is typically dominated by soot-like elemental carbon (EC).
Organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths
and the absorbing organics are referred to as brown carbon (BrC; Alexander et al., 2008).
These two aerosols contribute to solar radiative forcing through absorption of solar
radiation and heating of the absorbing aerosol layer, but most optical instruments that
quantify light absorption are unable to distinguish one type of absorbing aerosol
from another (Moosmüller et al. 2009). In this study, we separate total aerosol
absorption from these two different light absorbers from co-located simultaneous
in-situ measurements, such as Continuous Soot Monitoring System (COSMOS),
Continuous Light Absorption Photometer (CLAP) and Sunset EC/OC analyzer, at
Gosan climate observatory, Korea. We determine the mass absorption cross-section
(MAC) of BC, and then estimate the contribution of BC and BrC on aerosol light
absorption, together with a global 3-D chemical transport model (GEOS-Chem)
simulation. At 565 nm wavelength, BC MAC is found to be about 5.4±2.8 m2 g−1 from
COSMOS and Sunset EC/OC analyzer measurements during January-May 2012. This
value is similar to those from Alexander et al. (2008; 4.3 ∼ 4.8 m2 g−1 at 550 nm)
and Chung et al. (2012; 5.1 m2 g−1 at 520 nm), but slightly lower than Bond and
Bergstrom (2006; 7.5±1.2 m2 g−1 at 550 nm). The COMOS BC mass concentration
calculated with 5.4 m2 g−1 of BC MAC shows a good agreement with thermal
EC concentration, with a good slope (1.1). Aerosol absorption coefficient and BC
mass concentration from COSMOS, meanwhile, are approximately 25 ∼ 30 %
lower than those of CLAP. This difference can be attributable to the contribution of
volatile light-absorbing aerosols (i.e., BrC). The absorption coefficient of BrC,
which is determined by the difference of absorption coefficients from CLAP and
COSMOS measurements, increases with increasing thermal OC mass concentration.
Monthly variation of BC and BrC absorption coefficients estimated from in-situ
measurements and GEOS-Chem model simulation are generally well agreed, even though
GEOS-Chem simulation overestimates BC absorption coefficient while underestimates BrC
absorption coefficient. Here, we note that MAC of 5.4 m2 g−1 and3.8 m2 g−1 (taken
from Alexander et al., 2008) are used to calculate aerosol absorption coefficient of
BC and BrC, respectively. The contribution of BC to aerosol light absorption is
estimated to be about 70∼75%, while BrC accounts for about 25∼30% of total
aerosol light absorption, having a significant climatic implication in East Asia. |
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