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| Titel |
Exploring high resolution measurements of ozone depletion chemistry in coastal Antarctica through use of a 1D marine boundary layer chemistry model (MISTRA) |
| VerfasserIn |
Zak Buys, Anna Jones, Roland von Glasow, Neil Brough, Greg Huey, Dave Tanner |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057235
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| Zusammenfassung |
| Tropospheric Ozone Depletion Events (ODEs) have been known to occur in polar
regions for over 20 years. During such events, ozone concentrations can fall from
background amounts to below instrumental detection limits within a few minutes
and remain suppressed for on the order of hours to days. The chemical destruction
of ozone is driven by halogens (especially bromine radicals) that have a source
associated with the sea ice zone. Although our knowledge of ODEs has increased
greatly since their discovery, some of the key processes involved are not yet fully
understood.
In 2007, year round measurements were made at the British Antarctic Survey
station Halley, in coastal Antarctica, using a Chemical Ionisation Mass Spectrometer
(CIMS). During specific periods in the spring the CIMS was configured to measure
concentrations of BrO, Br2 and BrCl. In addition, concurrent measurements of surface ozone
and local meteorology were made. Due to the rapid photolysis of Br2 and BrCl
their daytime concentrations should be nil, however we see a clear signal for both
species during the day. A recent paper by Neuman et al. (2010) has highlighted that
there is a conversion of HOBr to Br2 on the CIMS Teflon inlet when using this
technique.
We present here an analysis of these datasets and a model study looking at
halogen release, from a source region identified using HYSPLIT air parcel back
trajectories. A 1D Marine Boundary Layer (MBL) chemistry model (MISTRA; von
Glasow et al, 2002) has been modified to be representative of Antarctic conditions by
implementing; measurements from Halley station which include aerosol size distribution
and composition (Rankin and Wolff, 2003), local meteorology (Anderson et al.,
2008), and chemistry in the model. MISTRA was then used in box-model mode
in an attempt to reproduce these CIMS halogen measurements. We explore the
possibilities of halogen release which varies with Solar Zenith Angle (SZA) and
has no contribution from HOBr, and constant halogen release (here in the form
of Br2 only) from a source region which includes HOBr conversion to Br2 and
BrCl.
Although results from both studies show some agreement with the daytime concentrations
of Br2 and BrCl as measured by the CIMS in spring at Halley, the recent study by Neuman et
al. (2010) would suggest that HOBr conversion should be included to correctly reproduce the
CIMS daytime measurements. |
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