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| Titel |
Possible catalytic effects of ice particles on the production of NOx by lightning discharges |
| VerfasserIn |
H. S. Peterson, W. H. Beasley |
| 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. 19 ; Nr. 11, no. 19 (2011-10-14), S.10259-10268 |
| Datensatznummer |
250010124
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| Publikation (Nr.) |
 copernicus.org/acp-11-10259-2011.pdf |
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| Zusammenfassung |
| It is well known that lightning produces NOx as a result of the high
temperatures in discharge channels. Since most viable proposed
electrification mechanisms involve ice crystals, it is reasonable to assume
that lightning discharge channels frequently pass through fields of ice
particles of various kinds. We address the question of whether ice crystals
may serve as catalysts for the production of NOx by lightning
discharges. If so, and if the effect is large, it would need to be taken
into account in estimates of global NOx production by lightning. In
this theoretical study, we make a series of plausible assumptions about the
temperature and concentration of reactant species in the environment of
discharges and we postulate a mechanism by which ice crystals are able to
adsorb nitrogen atoms. We then compare production rates between uncatalyzed
and catalyzed reactions at 2000 K, 3000 K, and 4000 K, which are reasonable
temperatures in lightning channels as they cool down. Ice crystal catalysis
is expected to produce 2.7 times more NO than if ice crystals were not
present. Catalyzed NO production rates are greater at 2000 K, whereas
uncatalyzed production rates are greater at 4000 K. Thus, temperatures that
favor rapid NO production without ice crystals adsorbing nitrogen atoms are
unfavorable for NO production in the presence of ice crystals, and vice
versa. The density of atmospheric ice crystals is much larger at 10 km where
intracloud (IC) flashes peak than at 5 km where cloud to ground (CG) flashes
peak, thus catalytic processes are expected to be more important for IC
flashes than CG flashes, perhaps explaining a portion of the discrepancy in
IC and CG production rates. |
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