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| Titel |
The HNO3 forming branch of the HO2 + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings |
| VerfasserIn |
O. A. Søvde, C. R. Hoyle, G. Myhre, I. S. A. Isaksen |
| 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. 17 ; Nr. 11, no. 17 (2011-09-01), S.8929-8943 |
| Datensatznummer |
250010046
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| Publikation (Nr.) |
 copernicus.org/acp-11-8929-2011.pdf |
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| Zusammenfassung |
| Recent laboratory measurements have shown the existence of a HNO3 forming
branch of the HO2 + NO reaction. This reaction is the main source of
tropospheric O3, through the subsequent photolysis of NO2, as well as
being a major source of OH. The branching of the reaction to HNO3 reduces
the formation of these species significantly, affecting O3 abundances,
radiative forcing and the oxidation capacity of the troposphere. The Oslo
CTM2, a three-dimensional chemistry transport model, is used to calculate
atmospheric composition and trends with and without the new reaction branch.
Results for the present day atmosphere, when both temperature and pressure
effects on the branching ratio are accounted for, show an 11 % reduction in
the calculated tropospheric burden of O3, with the main contribution
from the tropics. An increase of the global, annual mean methane lifetime by
10.9 %, resulting from a 14.1 % reduction in the global, annual mean
OH concentration is also found. Comparisons with measurements show
that including the new branch improves the modelled O3 in the Oslo CTM2,
but that it is not possible to conclude whether the NOy distribution
improves. We model an approximately 11 % reduction in the tropical
tropospheric O3 increase since pre-industrial times, and a 4 % reduction
of the increase in total tropospheric burden. Also, an 8 % decrease in the
trend of OH concentrations is calculated, when the new branch is accounted
for. The radiative forcing due to changes in O3 over the industrial era
was calculated as 0.33 W m−2, reducing to 0.26 W m−2 with the
new reaction branch. These results are significant, and it is important that
this reaction branching is confirmed by other laboratory groups. |
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