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| Titel |
Airborne tracer observations in the Arctic stratosphere during RECONCILE 2010: Quantification of transport and mixing |
| VerfasserIn |
C. Michael Volk, Elisabeth Hösen, Marcel vom Scheidt, Johannes Wintel, Jens-Uwe Grooß, Gebhardt Günther, Kaley A. Walker |
| 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 |
250056067
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| Zusammenfassung |
| We present new in situ tracer observations taken both in- and outside the 2010 Arctic
stratospheric vortex during the RECONCILE campaign and use them to quantify large-scale
diabatic descent, isentropic transport across the vortex boundary, and small-scale irreversible
mixing. The measurements (of N2O, CFC-11, CFC-12, Halon-1211, CH4, SF6, H2, and
CO2) were taken with the High Altitude Gas Analyzer (HAGAR) on board the M55
Geophysica aircraft during 13 flights from Kiruna, Sweden, between January and March
2010. Early winter reference profiles for a number of tracers are provided by satellite data
from the ACE-FTS experiment.
We use the observed distribution of the N2O mixing ratio as function of potential
temperature to define and calculate empirical fractions of vortex air for all sampled air
parcels. Vortex descent can then be derived to first order from the evolution of vertical tracer
profiles of nearly undiluted vortex samples. Transport across the vortex boundary is
quantified by analysing these fractions of vortex air in- and outside the vortex boundary as
function of potential temperature and equivalent latitude. Finally, irreversible isentropic
mixing of entrained extra-vortex air is assessed by analysing the evolution of the non-linear
tracer correlations throughout the winter.
We infer significant entrainment of mid- and even low-latitude air into the vortex after the
vortex split up and reformed in late February. Irreversible mixing of some of this entrained air
is also clearly evident as a mixing line in the CFC-11/N2O correlation at 500 K during the
last flight on March 10. Apart from this mixing signature, however, the CFC-11/N2O
correlation inside the vortex remains remarkably compact and unchanged between January
and March, suggesting that effects of mixing on trace gas budgets remained small
overall, at least until mid March. We will compare these results with simulations by
the Chemical Lagrangian Model of the Stratosphere (CLaMS), in particular with
calculated air mass origin spectra. Comparisons will also be made with observations
during the winter 2002/03 when substantial vortex dilution and irreversible mixing
had occurred throughout the vortex after a similar vortex split and reformation. |
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