 |
| Titel |
A global 3-D CTM evaluation of black carbon in the Tibetan Plateau |
| VerfasserIn |
C. He, Q. B. Li, K. N. Liou, J. Zhang, L. Qi, Y. Mao, M. Gao, Z. Lu, D. G. Streets, Q. Zhang, M. M. Sarin, K. Ram |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-11), S.7091-7112 |
| Datensatznummer |
250118882
|
| Publikation (Nr.) |
 copernicus.org/acp-14-7091-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| We systematically evaluate the black carbon (BC) simulations for 2006 over
the Tibetan Plateau by a global 3-D chemical transport model (CTM)
(GEOS-Chem) driven by GEOS-5 assimilated meteorological fields, using in situ
measurements of BC in surface air, BC in snow, and BC absorption aerosol
optical depth (AAOD). Using improved anthropogenic BC emission inventories
for Asia that account for rapid technology renewal and energy consumption
growth (Zhang et al., 2009; Lu et al., 2011) and improved global biomass
burning emission inventories that account for small fires (van der Werf et
al., 2010; Randerson et al., 2012), we find that model results of both BC in
surface air and in snow are statistically in good agreement with
observations (biases < 15%) away from urban centers. Model
results capture the seasonal variations of the surface BC concentrations at
rural sites in the Indo-Gangetic Plain, but the observed elevated values in
winter are absent. Modeled surface-BC concentrations are within a factor of 2 of the observations at remote sites. Part of the discrepancy is
explained by the deficiencies of the meteorological fields over the complex
Tibetan terrain. We find that BC concentrations in snow computed from
modeled BC deposition and GEOS-5 precipitation are spatiotemporally
consistent with observations (r = 0.85). The computed BC concentrations in
snow are a factor of 2–4 higher than the observations at several Himalayan
sites because of excessive BC deposition. The BC concentrations in snow are
biased low by a factor of 2 in the central plateau, which we attribute to
the absence of snow aging in the CTM and strong local emissions unaccounted
for in the emission inventories. Modeled BC AAOD is more than a factor of
2 lower than observations at most sites, particularly to the northwest of
the plateau and along the southern slopes of the Himalayas in winter and
spring, which is attributable in large part to underestimated emissions and
the assumption of external mixing of BC aerosols in the model. We find that
assuming a 50% increase of BC absorption associated with internal mixing
reduces the bias in modeled BC AAOD by 57% in the Indo-Gangetic Plain and
the northeastern plateau and to the northeast of the plateau, and by 16%
along the southern slopes of the Himalayas and to the northwest of the
plateau. Both surface BC concentration and AAOD are strongly sensitive to
anthropogenic emissions (from China and India), while BC concentration in
snow is especially responsive to the treatment of BC aerosol aging. We find
that a finer model resolution (0.5° × 0.667° nested over Asia) reduces the bias in modeled surface-BC concentration from
15 to 2%. The large range and non-homogeneity of discrepancies
between model results and observations of BC across the Tibetan Plateau
undoubtedly undermine current assessments of the climatic and hydrological
impact of BC in the region and thus warrant imperative needs for more extensive
measurements of BC, including its concentration in surface air and snow,
AAOD, vertical profile and deposition. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|