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| Titel |
Iodine chemistry in the troposphere and its effect on ozone |
| VerfasserIn |
A. Saiz-Lopez, R. P. Fernandez, C. Ordóñez, D. E. Kinnison, J. C. Gómez Martín, J.-F. Lamarque, S. Tilmes |
| 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. 23 ; Nr. 14, no. 23 (2014-12-10), S.13119-13143 |
| Datensatznummer |
250119228
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| Publikation (Nr.) |
 copernicus.org/acp-14-13119-2014.pdf |
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| Zusammenfassung |
| Despite the potential influence of iodine chemistry on the oxidizing capacity of
the troposphere, reactive iodine distributions and their impact on
tropospheric ozone remain almost unexplored aspects of the global atmosphere.
Here we present a comprehensive global modelling experiment aimed at
estimating lower and upper limits of the inorganic iodine burden and its
impact on tropospheric ozone. Two sets of simulations without and with the
photolysis of IxOy oxides (i.e. I2O2,
I2O3 and I2O4) were conducted to define the range of
inorganic iodine loading, partitioning and impact in the troposphere. Our
results show that the most abundant daytime iodine species throughout the
middle to upper troposphere is atomic iodine, with an annual average tropical
abundance of (0.15–0.55) pptv. We propose the existence of a "tropical
ring of atomic iodine" that peaks in the tropical upper troposphere
(~11–14 km) at the equator and extends to the sub-tropics
(30° N–30° S). Annual average daytime I / IO ratios
larger than 3 are modelled within the tropics, reaching ratios up to ~20
during vigorous uplift events within strong convective regions. We calculate
that the integrated contribution of catalytic iodine reactions to the total
rate of tropospheric ozone loss (IOx Loss) is 2–5 times larger
than the combined bromine and chlorine cycles. When IxOy
photolysis is included, IOx Loss represents an upper limit of
approximately 27, 14 and 27% of the tropical annual ozone loss for the
marine boundary layer (MBL), free troposphere (FT) and upper troposphere
(UT), respectively, while the lower limit throughout the tropical troposphere
is ~9%. Our results indicate that iodine is the second strongest
ozone-depleting family throughout the global marine UT and in
the tropical MBL. We suggest that (i) iodine sources and its chemistry need to be
included in global tropospheric chemistry models, (ii) experimental
programs designed to quantify the iodine budget in the troposphere should
include a strategy for the measurement of atomic I, and (iii)
laboratory programs are needed to characterize the photochemistry of higher
iodine oxides to determine their atmospheric fate since they can potentially
dominate halogen-catalysed ozone destruction in the troposphere. |
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