Regensburg 2016 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 3: Atmosphere - Aerosols
UP 3.3: Vortrag
Dienstag, 8. März 2016, 14:45–15:00, H41
Potential ice multiplication mechanism associated with freezing of large drizzle droplets — •Annika Lauber, Mona Schätzle, Patricia Handmann, Thomas Pander, Alexei Kiselev, and Thomas Leisner — Atmospheric Aerosol Research Department, Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
At temperatures above -38∘C freezing of a cloud droplet requires an ice nucleating particle (INP). However, at temperatures above -12∘C ice particles have been found in concentrations exceeding the number of INPs by 104. A possible explanation for this discrepancy is the fragmentation of supercooled drizzle drops at freezing.
To investigate this process, we are observing levitated freezing droplets with a high-speed video camera (up to 200,000 fps). Records of more than 10,000 individual freezing events already allowed the identification of two potentially important ice multiplication pathways: the expulsion of bubbles during the ice shell formation and the fragmentation of a droplet due to the growth of internal pressure.
To explore the fragmentation of large freezing drops, we have modified our setup to allow levitation of water drops with diameters of up to 500 µm. Based on the former and recently obtained measurement data, we discuss the size and temperature dependence of the suggested ice multiplication mechanism and its potential implication for cloud microphysics.