An ozone depletion event in the sub-arctic surface layer over Hudson Bay,Canada |
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| Authors: | B A Ridley T Zeng Y Wang E L Atlas E V Browell P G Hess J J Orlando K Chance A Richter |
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| Institution: | (1) Atmospheric Chemistry Division, NCAR, P. O. Box 3000, Boulder, CO 80307, USA;(2) School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA;(3) Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA;(4) Atmospheric Sciences, NASA Langley Research Center, Hampton, VA 23681, USA;(5) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA;(6) Institute of Environmental Physics, University of Bremen, P. O. Box 330 440, 28334 Bremen, Germany |
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| Abstract: | During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) program, aircraft flights during April 7–11, 2000
revealed a large area air mass capped below ∼500 m altitude over Hudson Bay, Canada in which ozone was reduced from normal
levels of 30–40 ppbv to as low as 0.5 ppbv. From some of the in-situ aircraft measurements, back-trajectory calculations,
the tropospheric column of BrO derived from GOME satellite measurements, and results from a regional model, we conclude that
the event did not originate from triggering of reactive halogen release in the sub-Arctic region of Hudson Bay but resulted
from such an event occurring at higher latitudes over the islands of the northern Canada Archipelago and nearby Arctic Ocean
with subsequent transport over a distance of 1,000–1,500 km to Hudson Bay. BrO
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remained active during this transport despite considerable changes in the conditions of the underlying surface suggesting
that chemical recycling during transport dominated any local halogen input from the surface. If all of the tropospheric column
density of BrO is distributed uniformly within the surface layer, then the mixing ratio of BrO derived from the satellite
measurements is at least a factor of 2–3 larger than derived indirectly from in situ aircraft measurements of the NO/NO2 ratio. |
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| Keywords: | Ozone Ozone depletion Bromine Hudson Bay Arctic TOPSE GOME |
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