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| Titel |
Analysis of transpacific transport of black carbon during HIPPO-3: implications for black carbon aging |
| VerfasserIn |
Z. Shen, J. Liu, L. W. Horowitz, D. K. Henze, S. Fan, H. II Levy, D. L. Mauzerall, J.-T. Lin, S. Tao |
| 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 ; 14, no. 12 ; Nr. 14, no. 12 (2014-06-25), S.6315-6327 |
| Datensatznummer |
250118835
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| Publikation (Nr.) |
 copernicus.org/acp-14-6315-2014.pdf |
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| Zusammenfassung |
Long-range transport of black carbon (BC) is a growing concern as a result
of the efficiency of BC in warming the climate and its adverse impact on
human health. We study transpacific transport of BC during HIPPO-3 using a
combination of inverse modeling and sensitivity analysis. We use the
GEOS-Chem chemical transport model and its adjoint to constrain Asian BC
emissions and estimate the source of BC over the North Pacific. We find that
different sources of BC dominate the transport to the North Pacific during
the southbound (29 March 2010) and northbound (13 April 2010) measurements
in HIPPO-3. While biomass burning in Southeast Asia (SE) contributes about
60% of BC in March, more than 90% of BC comes from fossil fuel and
biofuel combustion in East Asia (EA) during the April mission. GEOS-Chem
simulations generally resolve the spatial and temporal variation of BC
concentrations over the North Pacific, but are unable to reproduce the low
and high tails of the observed BC distribution. We find that the optimized
BC emissions derived from inverse modeling fail to improve model simulations
significantly. This failure indicates that uncertainties in BC removal as
well as transport, rather than in emissions, account for the major biases in
GEOS-Chem simulations of BC over the North Pacific.
The aging process, transforming BC from hydrophobic into hydrophilic form,
is one of the key factors controlling wet scavenging and remote
concentrations of BC. Sensitivity tests on BC aging (ignoring uncertainties
of other factors controlling BC long range transport) suggest that in order
to fit HIPPO-3 observations, the aging timescale of anthropogenic BC from
EA may be several hours (faster than assumed in most global models), while
the aging process of biomass burning BC from SE may occur much slower, with
a timescale of a few days. To evaluate the effects of BC aging and wet
deposition on transpacific transport of BC, we develop an idealized model of
BC transport. We find that the mid-latitude air masses sampled during
HIPPO-3 may have experienced a series of precipitation events, particularly
near the EA and SE source region. Transpacific transport of BC is sensitive
to BC aging when the aging rate is fast; this sensitivity peaks when the
aging timescale is in the range of 1–1.5 d. Our findings indicate that BC
aging close to the source must be simulated accurately at a process level in
order to simulate better the global abundance and climate forcing of BC. |
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