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Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

Umo, Nsikanabasi Silas; Wagner, Robert; Ullrich, Romy; Kiselev, Alexei; Saathoff, Harald; Weidler, Peter G.; Cziczo, D. J.; Leisner, Thomas; Möhler, Ottmar

Abstract (englisch):
Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, thereby impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with a particular CFA sample (CFA_UK), which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology (KIT), Germany, we observed a strong increase (at a threshold relative humidity with respect to ice of 101 %–105 %) in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000096897
Veröffentlicht am 29.07.2019
Coverbild
Zugehörige Institution(en) am KIT Institut für Funktionelle Grenzflächen (IFG)
Publikationstyp Zeitschriftenaufsatz
Jahr 2019
Sprache Englisch
Identifikator ISSN: 1680-7316, 1680-7324
KITopen-ID: 1000096897
Erschienen in Atmospheric chemistry and physics
Band 19
Heft 13
Seiten 8783-8800
Vorab online veröffentlicht am 10.07.2019
Nachgewiesen in Scopus
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