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| Titel |
Vortex-wide chlorine activation by a localized PSC event in the Arctic winter of 2009/10 |
| VerfasserIn |
Tobias Wegner, Lamont Poole, Ines Tritscher, Jens-Uwe Grooß, Hideaki Nakajima, Michael Pitts |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107439
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| Publikation (Nr.) |
 EGU/EGU2015-7142.pdf |
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| Zusammenfassung |
| During the polar night chlorine reservoir species react heterogeneously to photo-labile
chlorine compounds which drive ozone-loss cycles, eventually leading to the ozone-hole.
We investigate this process for the Arctic winter 2009/10 using satellite data and
model simulations. CALIPSO observations indicate localized Ppolar Stratospheric
Cloud (PSC) occurrences east of Greenland beginning of January 2010 with MLS
observations indicating a decrease in HCl mixing ratios co-located and downstream
of these PSCs. This localized PSC event has a bigger extent than mountain-wave
PSCs but still only covers a fraction of the entire vortex. Trajectory calculations
confirm that low HCl mixing ratios correspond to air that has passed through PSCs.
Following trajectories started in PCSs show that chlorine is activated in these cluods
nad subsequently this air with low HCl mixing ratios is adveted throughout the
vortex. Regions with high HCl mixing ratios correspond to air masses which haven’t
been exposed to PSC. After five days all vortex air has passed through the PSC
which shows that such localized PSCs can activate the entire vortex within a week.
Chlorine activation does not occur homogeneously throughout the vortex but rather in a
localized area with air constantly flowing through. This area corresponds to the
area where CALIPSO observed PSCs. Comparing the area where activation occurs
with indicators of chlorine activation such as TNAT and TACl we find that these
indicators overestimate the area where chlorine activation is expected to occur. In
addition, heterogeneous chemistry is modeled along the trajectories passing through
PSCs. Trajectory calculations are initialized upstream of PSCs with observations
from MLS, tracer-tracer correlations and non-observed species from a CLaMS
simulation. The CALIPSO backscatter product is used to estimate surface area
density. Our calculations of HCl agree well with MLS observations downstream of
PSCs. They also indicate that ClONO2 is the limiting factor in chlorine activation.
Overall, we find that heterogeneous chemistry can explain observations of HCl by
MLS and that chlorine activation is limited to the area where PSCs are present. |
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