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No anomalous supersaturation in ultracold cirrus laboratory experiments

Clouser, B. W.; Lamb, K. D.; Sarkozy, L. C.; Habig, J.; Ebert, V.; Saathoff, H.; Möhler, O.; Moyer, E. J.

High-altitude cirrus clouds are climatically important: their formation freeze-dries air ascending to the stratosphere to its final value, and their radiative impact is disproportionately large. However, their formation and growth are not fully understood, and multiple in situ aircraft campaigns have observed frequent and persistent apparent water vapor supersaturations of 5 %–25 % in ultracold cirrus (T<205 K), even in the presence of ice particles. A variety of explanations for these observations have been put forth, including that ultracold cirrus are dominated by metastable ice whose vapor pressure exceeds that of hexagonal ice. The 2013 IsoCloud campaign at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud and aerosol chamber allowed explicit testing of cirrus formation dynamics at these low temperatures. A series of 28 experiments allows robust estimation of the saturation vapor pressure over ice for temperatures between 189 and 235 K, with a variety of ice nucleating particles. Experiments are rapid enough (∼10 min) to allow detection of any metastable ice that may form, as the timescale for annealing to hexagonal ice is hours or longer over the whole experimental temperature range. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000105703
Veröffentlicht am 10.02.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Atmosphärische Aerosolforschung (IMK-AAF)
KIT-Zentrum Klima und Umwelt (ZKU)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 1680-7316, 1680-7324
KITopen-ID: 1000105703
HGF-Programm 12.01.01 (POF III, LK 01) Clouds in a pertubed atmosphere
Weitere HGF-Programme 12.04.02 (POF III, LK 01) Cirrus Clouds
Erschienen in Atmospheric chemistry and physics
Verlag European Geosciences Union (EGU)
Band 20
Heft 2
Seiten 1089-1103
Schlagwörter Cirrus clouds
Nachgewiesen in Dimensions
Web of Science
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