Summertime NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?

S J.-B Bauguitte,H K Roscoe,W J Bloss,A Saiz-Lopez,P S Anderson,E W Wolff,M J Evans,R A Salmon,A E Jones,J M C Plane,J D Lee

doi:10.5194/acp-12-989-2012

Abstract

Abstract. 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.

Highlights

For the past two decades, polar boundary layer composition and photochemistry has been the focus of major field measurement campaigns undertaken in Arctic and Antarctic research stations.At Alert (Nunavut, Canada), the pioneering Polar Sunrise Experiments (e.g. Barrie et al, 1994) initially prompted our attention to boundary layer ozone depletion and Arctic haze pollution events
We describe a set of NOx measurements conducted at the Clean Air Sector Laboratory (CASLab) at the Halley Research Station, coastal Antarctica, during the CHemistry of the Antarctic Boundary Layer and Interface with Snow (CHABLIS) campaign (Jones et al, 2008)
The design of the NO2 photolytic converter (PLC) employed in this study was inspired by the narrow-band photolysis system described in Ryerson et al (2000), and employs an Oriel PhotoMax lamp housing

Summary

Introduction

For the past two decades, polar boundary layer composition and photochemistry has been the focus of major field measurement campaigns undertaken in Arctic and Antarctic research stations. At Alert (Nunavut, Canada), the pioneering Polar Sunrise Experiments (e.g. Barrie et al, 1994) initially prompted our attention to boundary layer ozone depletion and Arctic haze pollution events. This triggered further research, such as the Tropospheric Ozone Production around the Spring Equinox (TOPSE) airborne missions flown by the NCAR C130 research aircraft into the high Canadian Arctic during Spring 2000 (Atlas et al, 2003). Similar long-term and summer intensive measurements campaign were conducted at the Summit station on the Greenland icecap Similar long-term and summer intensive measurements campaign were conducted at the Summit station on the Greenland icecap (e.g. Dibb et al, 1998, 2002; Honrath et al, 2002)

Methods

Results

Conclusion