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Verfasst von:Duft, Denis [VerfasserIn]   i
 Nachbar, Mario [VerfasserIn]   i
 Leisner, Thomas [VerfasserIn]   i
Titel:Unravelling the microphysics of polar mesospheric cloud formation
Verf.angabe:Denis Duft, Mario Nachbar, and Thomas Leisner
E-Jahr:2019
Jahr:06 Mar 2019
Umfang:9 S.
Fussnoten:Gesehen am 28.05.2019
Titel Quelle:Enthalten in: Atmospheric measurement techniques
Ort Quelle:Katlenburg-Lindau : Copernicus, 2008
Jahr Quelle:2019
Band/Heft Quelle:19(2019), 5, Seite 2871-2879
ISSN Quelle:1867-8548
Abstract:Polar mesospheric clouds are the highest water ice clouds occurring in the terrestrial atmosphere. They form in the polar summer mesopause, the coldest region in the atmosphere. It has long been assumed that these clouds form by heterogeneous nucleation on meteoric smoke particles which are the remnants of material ablated from meteoroids in the upper atmosphere. However, until now little was known about the properties of these nanometre-sized particles and application of the classical theory for heterogeneous ice nucleation was impacted by large uncertainties. In this work, we performed laboratory measurements on the heterogeneous ice formation process at mesopause conditions on small (r=1 to 3 nm) iron silicate nanoparticles serving as meteoric smoke analogues. We observe that ice growth on these particles sets in for saturation ratios with respect to hexagonal ice below Sh=50, a value that is commonly exceeded during the polar mesospheric cloud season, affirming meteoric smoke particles as likely nuclei for heterogeneous ice formation in mesospheric clouds. We present a simple ice-activation model based on the Kelvin–Thomson equation that takes into account the water coverage of iron silicates of various compositions. The activation model reproduces the experimental data very well using bulk properties of compact amorphous solid water. This is in line with the finding from our previous study that ice formation on iron silicate nanoparticles occurs by condensation of amorphous solid water rather than by nucleation of crystalline ice at mesopause conditions. Using the activation model, we also show that for iron silicate particles with dry radius larger than r=0.6 nm the nanoparticle charge has no significant effect on the ice-activation threshold.
DOI:doi:10.5194/acp-19-2871-2019
URL:Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.

Volltext ; Verlag: https://doi.org/https://doi.org/10.5194/acp-19-2871-2019
 Volltext: https://www.atmos-chem-phys.net/19/2871/2019/
 DOI: https://doi.org/10.5194/acp-19-2871-2019
Datenträger:Online-Ressource
Sprache:eng
K10plus-PPN:1666404799
Verknüpfungen:→ Zeitschrift

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