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| Titel |
The governing processes and timescales of stratosphere-to-troposphere transport and its contribution to ozone in the Arctic troposphere |
| VerfasserIn |
Q. Liang, A. R. Douglass, B. N. Duncan, R. S. Stolarski, J. C. Witte |
| 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 ; 9, no. 9 ; Nr. 9, no. 9 (2009-05-11), S.3011-3025 |
| Datensatznummer |
250007269
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| Publikation (Nr.) |
 copernicus.org/acp-9-3011-2009.pdf |
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| Zusammenfassung |
| We used the seasonality of a combination of atmospheric trace gases and
idealized tracers to examine stratosphere-to-troposphere transport and its
influence on tropospheric composition in the Arctic. Maximum
stratosphere-to-troposphere transport of CFCs and O3 occurs in April as
driven by the Brewer-Dobson circulation. Stratosphere-troposphere exchange
(STE) occurs predominantly between 40° N to 80° N with stratospheric
influx in the mid-latitudes (30–70° N) accounting for 67–81% of the
air of stratospheric origin in the Northern Hemisphere extratropical
troposphere. Transport from the lower stratosphere to the lower troposphere
(LT) takes three months on average, one month to cross the tropopause, the
second month to travel from the upper troposphere (UT) to the middle
troposphere (MT), and the third month to reach the LT. During downward
transport, the seasonality of a trace gas can be greatly impacted by wet
removal and chemistry. A comparison of idealized tracers with varying
lifetimes suggests that when initialized with the same concentrations and
seasonal cycles at the tropopause, trace gases that have shorter lifetimes
display lower concentrations, smaller amplitudes, and earlier seasonal
maxima during transport to the LT. STE contributes to O3 in the Arctic
troposphere directly from the transport of O3 and indirectly from the
transport of NOy. Direct transport of O3 from the stratosphere
accounts for 78% of O3 in the Arctic UT with maximum contributions
occurring from March to May. The stratospheric contribution decreases
significantly in the MT/LT (20–25% of total O3) and shows a very
weak March–April maximum. Our NOx budget analysis in the Arctic UT
shows that during spring and summer, the stratospheric injection of
NOy-rich air increases NOx concentrations above the 20 pptv
threshold level, thereby shifting the Arctic UT from a regime of net
photochemical ozone loss to one of net production with rates as high as +16 ppbv/month. |
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