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| Titel |
The 2009–2010 Arctic polar stratospheric cloud season: a CALIPSO perspective |
| VerfasserIn |
M. C. Pitts, L. R. Poole, A. Dörnbrack, L. W. Thomason |
| 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 ; 11, no. 5 ; Nr. 11, no. 5 (2011-03-10), S.2161-2177 |
| Datensatznummer |
250009453
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| Publikation (Nr.) |
 copernicus.org/acp-11-2161-2011.pdf |
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| Zusammenfassung |
| Spaceborne lidar measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared
Pathfinder Satellite Observations) are used to provide a vortex-wide
perspective of the 2009–2010 Arctic PSC (polar stratospheric cloud) season
to complement more focused measurements from the European Union RECONCILE
(reconciliation of essential process parameters for an enhanced
predictability of Arctic stratospheric ozone loss and its climate
interactions) field campaign. The 2009–2010 Arctic winter was unusually cold
at stratospheric levels from mid-December 2009 until the end of January
2010, and was one of only a few winters from the past fifty-two years with
synoptic-scale regions of temperatures below the frost point. More PSCs were
observed by CALIPSO during the 2009–2010 Arctic winter than in the previous
three Arctic seasons combined. In particular, there were significantly more
observations of high number density NAT (nitric acid trihydrate) mixtures
(referred to as Mix 2-enh) and ice PSCs. We found that the 2009–2010 season
could roughly be divided into four periods with distinctly different PSC
optical characteristics. The early season (15–30 December 2009) was
characterized by patchy, tenuous PSCs, primarily low number density
liquid/NAT mixtures. No ice clouds were observed by CALIPSO during this
early phase, suggesting that these early season NAT clouds were formed
through a non-ice nucleation mechanism. The second phase of the season (31 December 2009–14 January 2010) was characterized by frequent mountain
wave ice clouds that nucleated widespread NAT particles throughout the
vortex, including Mix 2-enh. The third phase of the season (15–21 January 2010) was characterized by synoptic-scale temperatures below the frost point
which led to a rare outbreak of widespread ice clouds. The fourth phase of
the season (22–28 January) was characterized by a major stratospheric
warming that distorted the vortex, displacing the cold pool from the vortex
center. This final phase was dominated by STS (supercooled ternary solution)
PSCs, although NAT particles may have been present in low number densities,
but were masked by the more abundant STS droplets at colder temperatures. We
also found distinct variations in the relative proportion of PSCs in each
composition class with altitude over the course of the 2009–2010 Arctic
season. Lower number density liquid/NAT mixtures were most frequently
observed in the lower altitude regions of the clouds (below ~18–20 km), which is consistent with CALIPSO observations in the Antarctic. Higher
number density liquid/NAT mixtures, especially Mix 2-enh, were most
frequently observed at altitudes above 18–20 km, primarily downstream of
wave ice clouds. This pattern is consistent with the conceptual model
whereby low number density, large NAT particles are precipitated from higher
number density NAT clouds (i.e. mother clouds) that are nucleated downstream
of mountain wave ice clouds. |
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