München 2019 – scientific programme

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UP: Fachverband Umweltphysik

UP 7: Clouds and aerosols

UP 7.2: Talk

Wednesday, March 20, 2019, 16:50–17:10, HS 22

Secondary Ice Production by drizzle droplets freezing in free fall — •Alice Keinert¹, Alexei Kiselev¹, Nadine Tüllmann¹, and Thomas Leisner^1,2 — ¹Institute of Meteorology and Climate Research - Atmospheric Aerosol Research Department, Karlsruhe Institute of Technology, Karlsruhe, Germany — ²Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany

The excess concentration of ice crystals as compared to the concentration of ice nuclei in cumuli has been one of the longest debated issues in cloud physics. Several ice multiplication mechanisms have been proposed to explain this discrepancy, with the Hallett-Mossop mechanism being the most well-known. Recent in-cloud observations have underlined the importance of secondary ice production upon shattering of freezing drizzle droplets. In this presentation, we report the recent results of the experimental study aimed to clarify the physics of this mechanism and to investigate its dependence on the environmental parameters. As in the recent study (Lauber et al., 2018), we levitate supercooled water droplets in an electrodynamic balance and observe the freezing process with a high-speed video camera. However, in the new setup the droplets are exposed to the gas flow mimicking the free fall at terminal velocity. We observe a very strong enhancement of shattering probability compared to the previous studies conducted under stagnant flow conditions.

Lauber, A., A. Kiselev, T. Pander, P. Handmann, and T Leisner (2018). "Secondary Ice Formation during Freezing of Levitated Droplets", Journal of the Atmospheric Sciences 75, pp. 2815-2826.