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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 17 | Copyright
Atmos. Chem. Phys., 17, 10733-10741, 2017
https://doi.org/10.5194/acp-17-10733-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 13 Sep 2017

Research article | 13 Sep 2017

Direct molecular-level characterization of different heterogeneous freezing modes on mica – Part 1

Ahmed Abdelmonem Ahmed Abdelmonem
  • Institute of Meteorology and Climate Research – Atmospheric Aerosol Research (IMKAAF), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany

Abstract. The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface–water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real-time molecular-level comparison of different freezing modes on the surface of an atmospherically relevant mineral surface (mica) under varying supersaturation conditions using second-harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one- and two-stage freezing). The nonlinear signal at the water–mica interface was found to drop following the formation of a thin film on the surface regardless of (1) the formed phase (liquid or ice) and (2) the freezing path (one or two step), indicating similar molecular structuring. The results also revealed a transient phase of ice at water–mica interfaces during freezing, which has a lifetime of around 1min. Such information will have a significant impact on climate change, weather modification, and the tracing of water in hydrosphere studies.

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On the basis of supercooled SHG spectroscopy, I report molecular-level evidence for the existence of one- and two-step deposition freezing depending on the surface type and the supersaturation conditions. In addition, immersion freezing shows a transient ice phase with a lifetime of c. 1 min. This study provides new insights into atmospheric processes and can impact various industrial and research branches, particularly climate change, weather modification, and tracing water in the hydrosphere.
On the basis of supercooled SHG spectroscopy, I report molecular-level evidence for the...
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