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| Titel |
Development of a parameterization of black carbon aging for use in general circulation models |
| VerfasserIn |
N. Oshima, M. Koike |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 2 ; Nr. 6, no. 2 (2013-03-01), S.263-282 |
| Datensatznummer |
250017791
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| Publikation (Nr.) |
 copernicus.org/gmd-6-263-2013.pdf |
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| Zusammenfassung |
| A parameterization of black carbon (BC) aging in the atmosphere is developed
for use in general circulation models (GCMs) that separately treat
hydrophobic BC and hydrophilic BC modes but do not explicitly calculate the
aging processes of BC. The rate of BC aging is expressed as the conversion
rate from hydrophobic BC to hydrophilic BC modes (i.e., inverse of the
e-folding time of the conversion, 1/τBC). In this study, the
conversion rates are estimated using results of detailed calculations by a
size and mixing state resolved aerosol box model with numerous initial
conditions. We introduce a new concept, the hydrophobic-BC-mass-normalized
coating rate (VBC), defined as the rate of increase of the mass
concentration of condensed materials on hydrophobic BC normalized by the
hydrophobic BC mass concentration. Although the conversion rate largely
varies depending on the atmospheric conditions and the concentrations of
chemical species, we find that the variations of the conversion rate are
generally expressed well by a unique function of VBC for given lognormal
size distributions of hydrophobic BC. The parameterized conversion rate is
expressed as a function of VBC, which enables the representation of
diurnal and seasonal variations of the BC aging rate and its spatial
differences in polluted and clean air, while other widely used constant
conversion rates cannot. Application of our newly developed parameterization
to GCMs will provide more reliable estimates of the spatial distribution of
BC and its radiative effects at regional and global scales. |
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