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| Titel |
Influence of surface morphology on the immersion mode ice nucleation efficiency of hematite particles |
| VerfasserIn |
N. Hiranuma, N. Hoffmann, A. Kiselev, A. Dreyer, K. Zhang, G. Kulkarni, T. Koop, O. Möhler |
| 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 ; 14, no. 5 ; Nr. 14, no. 5 (2014-03-05), S.2315-2324 |
| Datensatznummer |
250118461
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| Publikation (Nr.) |
 copernicus.org/acp-14-2315-2014.pdf |
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| Zusammenfassung |
| In this paper, the effect of the morphological modification of aerosol
particles with respect to heterogeneous ice nucleation is comprehensively
investigated for laboratory-generated hematite particles as a model
substrate for atmospheric dust particles. The surface-area-scaled ice
nucleation efficiencies of monodisperse cubic hematite particles and milled
hematite particles were measured with a series of expansion cooling
experiments using the Aerosol Interaction and Dynamics in the Atmosphere
(AIDA) cloud simulation chamber. Complementary offline characterization of
physico-chemical properties of both hematite subsets were also carried out
with scanning electron microscopy (SEM), energy dispersive X-ray (EDX)
spectroscopy, dynamic light scattering (DLS), and an electro-kinetic
particle charge detector to further constrain droplet-freezing measurements
of hematite particles. Additionally, an empirical parameterization derived
from our laboratory measurements was implemented in the single-column
version of the Community Atmospheric Model version 5 (CAM5) to investigate
the model sensitivity in simulated ice crystal number concentration on
different ice nucleation efficiencies. From an experimental perspective, our
results show that the immersion mode ice nucleation efficiency of milled
hematite particles is almost an order of magnitude higher at −35.2 °C
< T < −33.5 °C than that of the cubic hematite
particles, indicating a substantial effect of morphological irregularities
on immersion mode freezing. Our modeling results similarly show that the
increased droplet-freezing rates of milled hematite particles lead to about
one order magnitude higher ice crystal number in the upper troposphere than
cubic hematite particles. Overall, our results suggest that the surface
irregularities and associated active sites lead to greater ice activation
through droplet freezing. |
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