Summertime NOx measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles? 1British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
2School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
3School of Earth and the Environment, University of Leeds, LS2 9JT, UK
4School of Environmental Sciences, UEA, Norwich NR4 7TJ, UK
*now at: Facility for Airborne Atmospheric Measurements, Natural Environment Research Council, Cranfield, Bedfordshire, MK43 0AL, UK
**now at: School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT, UK
***now at: University of York/National Centre for Atmospheric Science, Department of Chemistry, University of York, York, YO10 5DD, UK
****now at: Laboratorio de Ciencias de la Atmósfera y el Clima, Consejo Superior de Investigaciones Científicas (CSIC), c/Rio Cabriel S/N, 45007 Toledo, Spain
*****now at: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
Received: 17 Jul 2009 – Published in Atmos. Chem. Phys. Discuss.: 29 Sep 2009Abstract. 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.
Revised: 21 Nov 2011 – Accepted: 11 Jan 2012 – Published: 19 Jan 2012
Citation: Bauguitte, S. J.-B., Bloss, W. J., Evans, M. J., Salmon, R. A., Anderson, P. S., Jones, A. E., Lee, J. D., Saiz-Lopez, A., Roscoe, H. K., Wolff, E. W., and Plane, J. M. C.: Summertime NOx measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?, Atmos. Chem. Phys., 12, 989-1002, doi:10.5194/acp-12-989-2012, 2012.