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| Titel |
Seasonal variability and long-term evolution of tropospheric composition in the tropics and Southern Hemisphere |
| VerfasserIn |
K. M. Wai, S. Wu, A. Kumar, H. Liao |
| 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. 10 ; Nr. 14, no. 10 (2014-05-19), S.4859-4874 |
| Datensatznummer |
250118721
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| Publikation (Nr.) |
 copernicus.org/acp-14-4859-2014.pdf |
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| Zusammenfassung |
| Impacts on tropospheric composition in the tropics and the Southern
Hemisphere from biomass burning and other emission sources are studied using
a global chemical transport model, surface measurements and satellite
retrievals. Seasonal variations in observed CO at remote island sites are
examined. Easter Island (eastern Pacific Ocean) is impacted indirectly by
the hemispheric zonal transport of CO due to the burning in southern Africa/South
America, via the westerlies. An increasing trend in CO by 0.33 ppb yr−1
in the past decade at Ascension Island is attributed to the
combined effects of South American/southern Africa burnings and the
increases in CH4 level. Compared to Easter Island and Ascension Island,
much less contribution from biomass burning to atmospheric CO is found at
the island of Mahé (western Indian Ocean), where the total CO peaks in
January–February, reflecting the contributions of anthropogenic emissions
from India. We also examine the 2000–2050 changes in atmospheric
composition in the tropics and the Southern Hemisphere driven by future
changes in emissions and climate. Changes in solar radiation (UV) over
South Atlantic Ocean (SAO) in future January have dominant effects on the
O3 distribution. More than 55% of O3 concentrations over the
SAO in both present-day and future September are not directly affected by
the emissions (including lightning) over the adjacent two continents but are
attributable to the transport of O3 from surrounding areas due to CO
and CH4 oxidation and stratospheric intrusion. High NOx emissions
in both continents in 2050s increase PAN concentrations over remote oceans
at the higher southern latitudes (> 35° S) as far as
those near Australia, affecting the O3 budget over there. Future
changes in biomass burning and anthropogenic NOx emissions in southern
Africa lead to a new area of high O3 concentrations near South Africa.
The resulted O3 outflow to the Indian Ocean is pronounced due to the
effects of the persistent anticyclone. A general reduction in future OH
radical concentrations is predicted over the remote marine boundary layer in
the tropics and the Southern Hemisphere, as a result of the increases in
CH4 and CO emissions. |
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