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| Titel |
Thermal stability analysis of particles incorporated in cirrus crystals and of non-activated particles in between the cirrus crystals: comparing clean and polluted air masses |
| VerfasserIn |
M. Seifert, J. Ström, R. Krejci, A. Minikin, A. Petzold, J.-F. Gayet, H. Schlager, H. Ziereis, U. Schumann, J. Ovarlez |
| 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 ; 4, no. 5 ; Nr. 4, no. 5 (2004-08-23), S.1343-1353 |
| Datensatznummer |
250001944
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| Publikation (Nr.) |
 copernicus.org/acp-4-1343-2004.pdf |
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| Zusammenfassung |
| A thermal volatility technique is used to provide indirect information about
the chemical composition of the aerosol involved in cirrus cloud formation.
The fraction of particles that disappears after being heated to 125°C
is termed volatile and the fraction that disappears between 125 and
250°C is termed semi-volatile. Particles that still remain after being
heated to 250°C make up the non-volatile fraction. The thermal
composition of residual particles remaining from evaporated cirrus crystals
is presented and compared to interstitial aerosol particles (non-activated
particles in between the cirrus crystals) for two temperature regimes (cold:
T< -38°C, warm: -38≤T< -23°C), based on in-situ
observations. The observations were conducted in cirrus clouds in the
Southern Hemisphere (SH) and Northern Hemisphere (NH) midlatitudes during
the INCA project. In the cold temperature regime, the non-volatile fraction
of the residual particles was typically in the range 10 to 30% in the NH
and 30 to 40% in the SH. In the warm temperature regime, the non-volatile
residual fraction was typically 10 to 30% (NH) and 20 to 40% (SH). At
high crystal number densities the non-volatile fraction in both temperature
regimes was even higher: in the range of 30 to 40% (NH) and 40 to 50%
(SH). The semi-volatile fraction was typically less than 10% in both
hemispheres, causing the volatile fraction to essentially be a complement to
the non-volatile fraction. In terms of the fractioning into the three types
of particles, the SH cold case is clearly different compared to the other
three cases (the two warm cases and the cold NH case), which share many
features. In the NH data the distribution of different particle types does
not seem to be temperature dependent. In all the cases, the non-volatile
fraction is enriched in the residual particles compared to the fractions
observed for the interstitial particles. This enrichment corresponds to
about 15 (NH) and 30 (SH) percent units in the two cold cases and to 15-25
(NH) and 25-35 (SH) percent units in the two warm cases. In the NH cold
case, there is a clear relation between the fractions observed in the
interstitial particles and what is observed in the residual particles. The
observed large fractions of non-volatile particles show that particles
forming ice crystals are not entirely made up of water-soluble sulfate
particles. |
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