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| Titel |
Denitrification in Arctic winter 2009/10: Study on shape and morphology of large dimension HNO3-containing particles |
| VerfasserIn |
Wolfgang Woiwode, Jens-Uwe Grooß, Hermann Oelhaf, Stephan Borrmann, Andreas Ebersoldt, Wiebke Frey, Thomas Gulde, Sergej Molleker, Christof Piesch, Hans Schlager, Johannes Orphal |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082775
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| Zusammenfassung |
| Flights of the high altitude aircraft M55 Geophysica in January 2010 during the
RECONCILE campaign (Reconciliation of essential process parameters for an enhanced
predictability of Arctic stratospheric ozone loss and its climate interactions) allowed probing
polar stratospheric clouds inside the Arctic polar vortex with in situ instruments.
Measurements by the Forward Scattering Spectrometer Probe model 100 (FSSP-100)
frequently indicated large dimension potentially HNO3-containing particles with maximum
sizes around 30 μm in diameter when data processing was carried out assuming
spherical particles. Such large particles can hardly be reconciled with current theory
of nucleation and growth of HNO3-containing particles capable of denitrification
(i.e. Nitric Acid Trihydrate (NAT)) when assuming spherical shape and compact
morphology.
We try to solve this issue by applying Chemical Transport Modelling with CLaMS
(Chemical Lagrangian Model of the Stratosphere) and infrared remote sensing
measurements from MIPAS-STR (Michelson Interferometer for Passive Atmospheric
Sounding-STRatospheric aircraft) aboard the Geophysica aircraft to test the impact of
alternative particle morphology and shape on HNO3 redistribution. Alternative particle
morphologies and shapes result in reduced particle sedimentation speeds compared to mass
equivalent spherical particles and therefore in modified vertical redistribution patterns of
HNO3.
Assuming denitrification by particles composed of NAT, our study indicates that spherical
“flake-like” particles with low mass density are unlikely to cause the observed denitrification.
The assumption of aspheric particles (i.e. platelets or needles) with moderate aspect ratios is
supported by our findings and offers an explanation for the particle sizes that have been
derived from the in situ particle measurements. Reduced particle sedimentation speed through
aspheric particle shape significantly influences denitrification efficiency. Consideration of this
aspect therefore can improve chemical transport and climate chemistry modelling. |
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