Summertime NO x measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?

NO x measurements were conducted at the Halley Research Station, coastal Antarctica, during the austral summer period 1 January–10 February 2005. A clear NO x diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NO x...

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Bibliographic Details
Published in:Atmospheric Chemistry and Physics
Main Authors: H. K. Roscoe, E. W. Wolff, A. Saiz-Lopez, J. D. Lee, A. E. Jones, P. S. Anderson, R. A. Salmon, M. J. Evans, W. J. Bloss, S. J.-B. Bauguitte, J. M. C. Plane
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2012
Subjects:
Physics
QC1-999
Chemistry
QD1-999
Austral
Halley Research Station
Antarc*
Antarctica
Online Access:https://doi.org/10.5194/acp-12-989-2012
https://doaj.org/article/9010588279cc44a6aae9d736a35ad09f
Description
Summary:NO x measurements were conducted at the Halley Research Station, coastal Antarctica, during the austral summer period 1 January–10 February 2005. A clear NO x diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NO x concentrations peaked (24 pptv) between 19:00–20:00 GMT, approximately 5 h after local solar noon. An optimised box model of NO x concentrations based on production from in-snow nitrate photolysis and chemical loss derives a mean noon emission rate of 3.48 × 10 8 molec cm −2 s −1 , assuming a 100 m boundary layer mixing height, and a relatively short NO x lifetime of ~6.4 h. This emission rate compares to directly measured values ranging from 2.1 to 12.6 × 10 8 molec cm −2 s −1 made on 3 days at the end of the study period. Calculations of the maximum rate of NO 2 loss via a variety of conventional HO x and halogen oxidation processes show that the lifetime of NO x is predominantly controlled by halogen processing, namely BrNO 3 and INO 3 gas-phase formation and their subsequent heterogeneous uptake. Furthermore the presence of halogen oxides is shown to significantly perturb NO x concentrations by decreasing the NO/NO 2 ratio. We conclude that in coastal Antarctica, the potential ozone production efficiency of NO x emitted from the snowpack is mitigated by the more rapid NO x loss due to halogen nitrate hydrolysis.

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