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Volume 15, issue 14
Atmos. Chem. Phys., 15, 7859–7875, 2015
https://doi.org/10.5194/acp-15-7859-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Oxidant Production over Antarctic Land and its Export...

Atmos. Chem. Phys., 15, 7859–7875, 2015
https://doi.org/10.5194/acp-15-7859-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Jul 2015

Research article | 17 Jul 2015

Atmospheric nitrogen oxides (NO and NO2) at Dome C, East Antarctica, during the OPALE campaign

M. M. Frey1, H. K. Roscoe1, A. Kukui2,3, J. Savarino4,5, J. L. France6, M. D. King7, M. Legrand4,5, and S. Preunkert4,5 M. M. Frey et al.
  • 1British Antarctic Survey, Natural Environment Research Council, Cambridge, UK
  • 2Laboratoire Atmosphère, Milieux et Observations Spatiales (LATMOS), UMR8190, CNRS-Université de Versailles Saint Quentin, Université Pierre et Marie Curie, Paris, France
  • 3Laboratoire de Physique et Chimie de l'Environnement et de l'Éspace (LPC2E), UMR6115 CNRS-Université d'Orléans, 45071 Orléans CEDEX 2, France
  • 4Université Grenoble Alpes, Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE), 38000 Grenoble, France
  • 5CNRS, Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE), 38000 Grenoble, France
  • 6School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
  • 7Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK

Abstract. Mixing ratios of the atmospheric nitrogen oxides NO and NO2 were measured as part of the OPALE (Oxidant Production in Antarctic Lands & Export) campaign at Dome C, East Antarctica (75.1° S, 123.3° E, 3233 m), during December 2011 to January 2012. Profiles of NOx mixing ratios of the lower 100 m of the atmosphere confirm that, in contrast to the South Pole, air chemistry at Dome C is strongly influenced by large diurnal cycles in solar irradiance and a sudden collapse of the atmospheric boundary layer in the early evening. Depth profiles of mixing ratios in firn air suggest that the upper snowpack at Dome C holds a significant reservoir of photolytically produced NO2 and is a sink of gas-phase ozone (O3). First-time observations of bromine oxide (BrO) at Dome C show that mixing ratios of BrO near the ground are low, certainly less than 5 pptv, with higher levels in the free troposphere. Assuming steady state, observed mixing ratios of BrO and RO2 radicals are too low to explain the large NO2 : NO ratios found in ambient air, possibly indicating the existence of an unknown process contributing to the atmospheric chemistry of reactive nitrogen above the Antarctic Plateau. During 2011–2012, NOx mixing ratios and flux were larger than in 2009–2010, consistent with also larger surface O3 mixing ratios resulting from increased net O3 production. Large NOx mixing ratios at Dome C arise from a combination of continuous sunlight, shallow mixing height and significant NOx emissions by surface snow (FNOx). During 23 December 2011–12 January 2012, median FNOx was twice that during the same period in 2009–2010 due to significantly larger atmospheric turbulence and a slightly stronger snowpack source. A tripling of FNOx in December 2011 was largely due to changes in snowpack source strength caused primarily by changes in NO3 concentrations in the snow skin layer, and only to a secondary order by decrease of total column O3 and associated increase in NO3 photolysis rates. A source of uncertainty in model estimates of FNOx is the quantum yield of NO3 photolysis in natural snow, which may change over time as the snow ages.

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Surprisingly large concentrations and flux of atmospheric nitrogen oxides were measured at Dome C, East Antarctica. It was found that the surface snow holds a significant reservoir of photochemically produced NOx and is a sink of gas-phase ozone. Main drivers of NOx snow emissions were large snow nitrate concentrations, with contributions of increased UV from decreases in stratospheric ozone. Observed halogen and hydroxyl radical concentrations were too low to explain large NO2:NO ratios.
Surprisingly large concentrations and flux of atmospheric nitrogen oxides were measured at Dome...
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