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  Comparative Study On Immersion Freezing Utilizing Single Droplet Levitation Methods

Szakáll, M., Debertshäuser, M., Lackner, C. P., Mayer, A., Eppers, O., Diehl, K., et al. (2020). Comparative Study On Immersion Freezing Utilizing Single Droplet Levitation Methods. Atmospheric Chemistry and Physics Discussions, 20. doi:10.5194/acp-2020-671.

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 Creators:
Szakáll, Miklos1, Author           
Debertshäuser, Michael, Author
Lackner, Christian Philip, Author
Mayer, Amelie, Author
Eppers, Oliver1, Author           
Diehl, Karoline1, Author           
Theis , Alexander, Author
Mitra, Subir Kumar1, Author           
Borrmann, Stephan1, Author           
Affiliations:
1Particle Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826291              

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 Abstract: Immersion freezing experiments were performed utilizing two distinct single-droplet levitation methods. In the Mainz vertical wind tunnel (M-WT) supercooled droplets of 700 μm diameter were freely floated in a vertical air stream at constant temperatures ranging from −5 °C to −30 °C where heterogeneous freezing takes place. These investigations under isothermal conditions allow applying the stochastic approach to analyze and interpret the results in terms of the freezing or nucleation rate. In the Mainz acoustic levitator (M-AL) 2 mm diameter drops were levitated while their temperature was continuously cooling from +20 °C to −28 °C by adapting to the ambient temperature. Therefore, in this case the singular approach was used for analysis. From the experiments, the densities of ice nucleating active sites (INAS) were obtained as function of temperature. The direct comparison of the results from two different instruments indicates a shift of the freezing temperatures towards lower values that was material dependent. As ice nucleating particles, seven materials were investigated, two representatives of biological species (fibrous and microcrystalline cellulose), four mineral dusts (feldspar, illite NX, montmorillonite, and kaolinite), and natural Sahara dust. Based on detailed analysis of our results we determined a material dependent temperature correction factor for each investigated particle type. The analysis allowed further classifying the investigated materials as single- or multiple-component. From our experiences during the present synergetic studies, we listed a number of suggestions for future experiments regarding cooling rates, determination of the drop temperature, purity of the water used to produce the drops, and characterization of the ice nucleating material. The observed freezing temperature shift is significantly important not only for the intercomparison of ice nucleation instruments with different cooling rates but also for cloud model simulations with high speed ascents of air masses.

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Language(s): eng - English
 Dates: 2020-08-05
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: No review
 Identifiers: DOI: 10.5194/acp-2020-671
 Degree: -

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Title: Atmospheric Chemistry and Physics Discussions
  Abbreviation : Atmos. Chem. Phys. Discuss.
Source Genre: Journal
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Publ. Info: Katlenburg-Lindau, Germany : European Geophysical Society, Copernicus Publ.
Pages: 41 Volume / Issue: 20 Sequence Number: - Start / End Page: - Identifier: ISSN: 1680-7367
CoNE: https://pure.mpg.de/cone/journals/resource/111076360006006