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| Titel |
Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign |
| VerfasserIn |
G. Li, N. Bei, X. Tie, L. T. Molina |
| 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 ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-01), S.5169-5182 |
| Datensatznummer |
250009795
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| Publikation (Nr.) |
 copernicus.org/acp-11-5169-2011.pdf |
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| Zusammenfassung |
| In the present study, the impact of aerosols on the
photochemistry in Mexico City is evaluated using the WRF-CHEM model for the
period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. An aerosol
radiative module has been developed with detailed consideration of aerosol
size, composition, and mixing. The module has been coupled into the WRF-CHEM
model to calculate the aerosol optical properties, including optical depth,
single scattering albedo, and asymmetry factor. Calculated aerosol optical
properties are in good agreement with the surface observations and aircraft
and satellite measurements during daytime. In general, the photolysis rates
are reduced due to the absorption by carbonaceous aerosols, particularly in
the early morning and late afternoon hours with a long aerosol optical path.
However, with the growth of aerosol particles and the decrease of the solar
zenith angle around noontime, aerosols can slightly enhance photolysis rates
when ultraviolet (UV) radiation scattering dominates UV absorption by
aerosols at the lower-most model layer. The changes in photolysis rates due
to aerosols lead to about 2–17 % surface ozone reduction during daytime in
the urban area in Mexico City with generally larger reductions during early
morning hours near the city center, resulting in a decrease of OH level by
about 9 %, as well as a decrease in the daytime concentrations of nitrate
and secondary organic aerosols by 5–6 % on average. In addition, the rapid
aging of black carbon aerosols and the enhanced absorption of UV radiation
by organic aerosols contribute substantially to the reduction of photolysis
rates. |
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