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Titel |
Temporal and spatial characteristics of ozone depletion events from measurements in the Arctic |
VerfasserIn |
J. W. Halfacre, T. N. Knepp, P. B. Shepson, C. R. Thompson, K. A. Pratt, B. Li, P. K. Peterson, S. J. Walsh, W. R. Simpson, P. A. Matrai, J. W. Bottenheim, S. Netcheva, D. K. Perovich, A. Richter |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1680-7316
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Digitales Dokument |
URL |
Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 10 ; Nr. 14, no. 10 (2014-05-20), S.4875-4894 |
Datensatznummer |
250118722
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Publikation (Nr.) |
copernicus.org/acp-14-4875-2014.pdf |
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Zusammenfassung |
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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