Summertime NOx measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?

Bauguitte, S. J.-B. and Bloss, W. J. and Evans, M. J. and Salmon, R. A. and Anderson, P. S. and Jones, A. E. and Lee, J. D. and Saiz-Lopez, A. and Roscoe, H. K. and Wolff, E. W. and Plane, J. M. C. (2012) Summertime NOx measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles? Atmospheric Chemistry and Physics, 12. pp. 989-1002. ISSN 1680-7316 eISSN 1680-7324 DOI 10.5194/acp-12-989-2012

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NOx measurements were conducted at the Halley Research Station, coastal Antarctica, during the austral summer period 1 January–10 February 2005. A clear NOx diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NOx concentrations peaked (24 pptv) between 19:00–20:00 GMT, approximately 5 h after local solar noon. An optimised box model of NOx concentrations based on production from in-snow nitrate photolysis and chemical loss derives a mean noon emission rate of 3.48 × 108 molec cm−2 s−1, assuming a 100 m boundary layer mixing height, and a relatively short NOx lifetime of ~6.4 h. This emission rate compares to directly measured values ranging from 2.1 to 12.6 × 108 molec cm−2 s−1 made on 3 days at the end of the study period. Calculations of the maximum rate of NO2 loss via a variety of conventional HOx and halogen oxidation processes show that the lifetime of NOx is predominantly controlled by halogen processing, namely BrNO3 and INO3 gas-phase formation and their subsequent heterogeneous uptake. Furthermore the presence of halogen oxides is shown to significantly perturb NOx concentrations by decreasing the NO/NO2 ratio. We conclude that in coastal Antarctica, the potential ozone production efficiency of NOx emitted from the snowpack is mitigated by the more rapid NOx loss due to halogen nitrate hydrolysis.

Item Type: Article
Additional Information: © Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License.
Uncontrolled Keywords: NIL AREP
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Atmospheric Chemistry and Physics
Volume: 12
Page Range: pp. 989-1002
Identification Number: 10.5194/acp-12-989-2012
Depositing User: Sarah Humbert
Date Deposited: 31 Aug 2013 14:48
Last Modified: 31 Aug 2013 14:48

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