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Volume 14, issue 10
Atmos. Chem. Phys., 14, 4875-4894, 2014
https://doi.org/10.5194/acp-14-4875-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 14, 4875-4894, 2014
https://doi.org/10.5194/acp-14-4875-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 May 2014

Research article | 20 May 2014

Temporal and spatial characteristics of ozone depletion events from measurements in the Arctic

J. W. Halfacre1, T. N. Knepp*,1, P. B. Shepson1,2, C. R. Thompson**,1, K. A. Pratt1,***, B. Li3,****, P. K. Peterson4, S. J. Walsh4, W. R. Simpson4, P. A. Matrai5, J. W. Bottenheim6, S. Netcheva7, D. K. Perovich8, and A. Richter9 J. W. Halfacre et al.
  • 1Department of Chemistry, Purdue University, West Lafayette, Indiana, USA
  • 2Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA
  • 3Department of Statistics, Purdue University, West Lafayette, Indiana, USA
  • 4Department of Chemistry, University of Alaska, Fairbanks, Alaska, USA
  • 5Bigelow Laboratory for Ocean Sciences, East Boothbay, Maine, USA
  • 6Air Quality Research Division, Environment Canada, Toronto, Ontario, Canada
  • 7Air Quality Processes Research Section, Environment Canada, Toronto, Ontario, Canada
  • 8US Army Cold Regions Research and Engineering Laboratory, Fairbanks, Alaska, USA
  • 9Institute of Environmental Physics, University of Bremen, Bremen, Germany
  • *now at: Science Systems and Applications, Inc., Hampton, Virginia, USA
  • **now at: Institute of Arctic and Alpine Research, University of Colorado at Boulder, Boulder, Colorado, USA
  • ***now at: Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
  • ****now at: Department of Statistics, University Illinois at Urbana-Champaign, Urbana, Illinois, USA

Abstract. Following polar sunrise in the Arctic springtime, tropospheric ozone episodically decreases rapidly to near-zero levels during ozone depletion events (ODEs). Many uncertainties remain in our understanding of ODE characteristics, including the temporal and spatial scales, as well as environmental drivers. Measurements of ozone, bromine monoxide (BrO), and meteorology were obtained during several deployments of autonomous, ice-tethered buoys (O-Buoys) from both coastal sites and over the Arctic Ocean; these data were used to characterize observed ODEs. Detected decreases in surface ozone levels during the onset of ODEs corresponded to a median estimated apparent ozone depletion timescale (based on both chemistry and the advection of O3-depleted air) of 11 h. If assumed to be dominated by chemical mechanisms, these timescales would correspond to larger-than-observed BrO mole fractions based on known chemistry and assumed other radical levels. Using backward air mass trajectories and an assumption that transport mechanisms dominate observations, the spatial scales for ODEs (defined by time periods in which ozone levels ≤15 nmol mol−1) were estimated to be 877 km (median), while areas estimated to represent major ozone depletions (<10 nmol mol−1) had dimensions of 282 km (median). These observations point to a heterogeneous boundary layer with localized regions of active, ozone-destroying halogen chemistry, interspersed among larger regions of previously depleted air that retain reduced ozone levels through hindered atmospheric mixing. Based on the estimated size distribution, Monte Carlo simulations showed it was statistically possible that all ODEs observed could have originated upwind, followed by transport to the measurement site. Local wind speed averages were low during most ODEs (median of ~3.6 m s−1), and there was no apparent dependence on local temperature.

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