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| Titel |
Lightning NOx, a key chemistry–climate interaction: impacts of future climate change and consequences for tropospheric oxidising capacity |
| VerfasserIn |
A. Banerjee, A. T. Archibald, A. C. Maycock, P. Telford, N. L. Abraham, X. Yang, P. Braesicke, J. A. Pyle |
| 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. 18 ; Nr. 14, no. 18 (2014-09-18), S.9871-9881 |
| Datensatznummer |
250119045
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| Publikation (Nr.) |
 copernicus.org/acp-14-9871-2014.pdf |
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| Zusammenfassung |
Lightning is one of the major natural sources of NOx in the atmosphere.
A suite of time slice experiments using a stratosphere-resolving
configuration of the Unified Model (UM), containing the United Kingdom
Chemistry and Aerosols sub-model (UKCA), has been performed to investigate
the impact of climate change on emissions of NOx from lightning
(LNOx) and to highlight its critical impacts on photochemical ozone
production and the oxidising capacity of the troposphere. Two Representative
Concentration Pathway (RCP) scenarios (RCP4.5 and RCP8.5) are explored.
LNOx is simulated to increase in a year-2100 climate by 33% (RCP4.5)
and 78% (RCP8.5), primarily as a result of increases in the depth of
convection. The total tropospheric chemical odd oxygen production
(P(Ox)) increases linearly with increases in total LNOx and
consequently, tropospheric ozone burdens of 29 ± 4 Tg(O3) (RCP4.5)
and 46 ± 4 Tg(O3) (RCP8.5) are calculated here. By prescribing a
uniform surface boundary concentration for methane in these simulations,
methane-driven feedbacks are essentially neglected. A simple estimate of the
contribution of the feedback reduces the increase in ozone burden to 24 and
33 Tg(O3), respectively. We thus show that, through changes in
LNOx, the effects of climate change counteract the simulated mitigation
of the ozone burden, which results from reductions in ozone precursor
emissions as part of air quality controls projected in the RCP scenarios.
Without the driver of increased LNOx, our simulations suggest that the
net effect of climate change would be to lower free tropospheric ozone.
In addition, we identify large climate-change-induced enhancements in the
concentration of the hydroxyl radical (OH) in the tropical upper troposphere
(UT), particularly over the Maritime Continent, primarily as a consequence
of greater LNOx. The OH enhancement in the tropics increases oxidation
of both methane (with feedbacks onto chemistry and climate) and very
short-lived substances (VSLS) (with implications for stratospheric ozone
depletion). We emphasise that it is important to improve our understanding
of LNOx in order to gain confidence in model projections of composition
change under future climate. |
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