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Titel |
Heterogeneous formation of polar stratospheric clouds – Part 2: Nucleation of ice on synoptic scales |
VerfasserIn |
I. Engel, B. P. Luo, M. C. Pitts, L. R. Poole, C. R. Hoyle, J.-U. Grooß, A. Dörnbrack, T. Peter |
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 ; 13, no. 21 ; Nr. 13, no. 21 (2013-11-06), S.10769-10785 |
Datensatznummer |
250085793
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Publikation (Nr.) |
copernicus.org/acp-13-10769-2013.pdf |
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Zusammenfassung |
This paper provides compelling evidence for the importance of heterogeneous
nucleation, likely on solid particles of meteoritic origin, and of
small-scale temperature fluctuations, for the formation of ice particles in
the Arctic stratosphere. During January 2010, ice PSCs (polar stratospheric
clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder
Satellite Observations) to have occurred on a synoptic scale
(~1000 km dimension). CALIPSO observations also showed widespread
PSCs containing NAT (nitric acid trihydrate) particles in December 2009,
prior to the occurrence of synoptic-scale regions of ice PSCs during
mid-January 2010. We demonstrate by means of detailed microphysical modeling
along air parcel trajectories that the formation of these PSCs is not readily
reconciled with expectations from the conventional understanding of PSC
nucleation mechanisms. The measurements are at odds with the previous
laboratory-based understanding of PSC formation, which deemed direct
heterogeneous nucleation of NAT and ice on preexisting solid particles
unlikely. While a companion paper (Part 1) addresses the heterogeneous
nucleation of NAT during December 2009, before the existence of ice PSCs,
this paper shows that also the large-scale occurrence of stratospheric ice in
January 2010 cannot be explained merely by homogeneous ice nucleation but
requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or
preexisting NAT particles. The required efficiency of the ice nuclei is
surprisingly high, namely comparable to that of known tropospheric ice nuclei
such as mineral dust particles. To gain model agreement with the ice number
densities inferred from observations, the presence of small-scale temperature
fluctuations, with wavelengths unresolved by the numerical weather prediction
models, is required. With the derived rate parameterization for heterogeneous
ice nucleation we are able to explain and reproduce CALIPSO observations
throughout the entire Arctic winter 2009/2010. |
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