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| Titel |
Coupling of HOx, NOx and halogen chemistry in the antarctic boundary layer |
| VerfasserIn |
W. J. Bloss, M. Camredon, J. D. Lee, D. E. Heard, J. M. C. Plane, A. Saiz-Lopez, S. J.-B. Bauguitte, R. A. Salmon, A. E. Jones |
| 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 ; 10, no. 21 ; Nr. 10, no. 21 (2010-11-01), S.10187-10209 |
| Datensatznummer |
250008861
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| Publikation (Nr.) |
 copernicus.org/acp-10-10187-2010.pdf |
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| Zusammenfassung |
| A modelling study of radical chemistry in the coastal Antarctic boundary
layer, based upon observations performed in the course of the CHABLIS
(Chemistry of the Antarctic Boundary Layer and the Interface with Snow)
campaign at Halley Research Station in coastal Antarctica during the austral
summer 2004/2005, is described: a detailed zero-dimensional photochemical box
model was used, employing inorganic and organic reaction schemes drawn from
the Master Chemical Mechanism, with additional halogen (iodine and bromine)
reactions added. The model was constrained to observations of long-lived
chemical species, measured photolysis frequencies and meteorological
parameters, and the simulated levels of HOx, NOx and XO
compared with those observed. The model was able to replicate the mean levels
and diurnal variation in the halogen oxides IO and BrO, and to reproduce
NOx levels and speciation very well. The NOx source term
implemented compared well with that directly measured in the course of the
CHABLIS experiments. The model systematically overestimated OH and HO2
levels, likely a consequence of the combined effects of (a) estimated physical
parameters and (b) uncertainties within the halogen, particularly iodine,
chemical scheme. The principal sources of HOx radicals were the
photolysis and bromine-initiated oxidation of HCHO, together with
O(1D) + H2O. The main sinks for HOx were peroxy
radical self- and cross-reactions, with the sum of all
halogen-mediated HOx loss processes accounting for 40% of the total
sink. Reactions with the halogen monoxides dominated
CH3O2-HO2-OH interconversion, with associated local chemical
ozone destruction in place of the ozone production which is associated with
radical cycling driven by the analogous NO reactions. The analysis highlights
the need for observations of physical parameters such as aerosol surface area
and boundary layer structure to constrain such calculations, and the
dependence of simulated radical levels and ozone loss rates upon a number of
uncertain kinetic and photochemical parameters for iodine species. |
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