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| Titel |
Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model |
| VerfasserIn |
R. M. Doherty, D. S. Stevenson, W. J. Collins, M. G. Sanderson |
| 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 ; 5, no. 12 ; Nr. 5, no. 12 (2005-12-05), S.3205-3218 |
| Datensatznummer |
250003189
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| Publikation (Nr.) |
 copernicus.org/acp-5-3205-2005.pdf |
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| Zusammenfassung |
| The impact of convection on tropospheric O3 and its precursors has been
examined in a coupled chemistry-climate model. There are two ways that
convection affects O3. First, convection affects O3 by vertical
mixing of O3 itself. Convection lifts lower tropospheric air to regions
where the O3 lifetime is longer, whilst mass-balance subsidence mixes
O3-rich upper tropospheric (UT) air downwards to regions where the
O3 lifetime is shorter. This tends to decrease UT O3 and the
overall tropospheric column of O3. Secondly, convection affects O3
by vertical mixing of O3 precursors. This affects O3 chemical
production and destruction. Convection transports isoprene and its
degradation products to the UT where they interact with lightning NOx
to produce PAN, at the expense of NOx. In our model, we find that
convection reduces UT NOx through this mechanism; convective
down-mixing also flattens our imposed profile of lightning emissions,
further reducing UT NOx. Over tropical land, which has large lightning
NOx emissions in the UT, we find convective lofting of NOx from
surface sources appears relatively unimportant. Despite UT NOx
decreases, UT O3 production increases as a result of UT HOx
increases driven by isoprene oxidation chemistry. However, UT O3 tends
to decrease, as the effect of convective overturning of O3 itself
dominates over changes in O3 chemistry. Convective transport also
reduces UT O3 in the mid-latitudes resulting in a 13% decrease in
the global tropospheric O3 burden. These results contrast with an
earlier study that uses a model of similar chemical complexity. Differences
in convection schemes as well as chemistry schemes – in particular
isoprene-driven changes are the most likely causes of such discrepancies.
Further modelling studies are needed to constrain this uncertainty range. |
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