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UP: Fachverband Umweltphysik
UP 2: Clouds and Aerosols
UP 2.2: Vortrag
Donnerstag, 2. September 2021, 14:20–14:35, H3
Thermal imaging of freezing drizzle droplets: pressure release events as a source of secondary ice particles — Judith Kleinheins1, Alexei Kiselev2, Alice Keinert2, Matthias Kind2,3, and •Thomas Leisner2,4 — 1Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland — 2Institute of Meteorology and Climate Research - Atmospheric Aeorosol Research, Karlsruhe Insitute of Technology, Karlsruhe, Germany — 3Institute of Thermal Process Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany — 4Institut für Umweltphysik, Universität Heidelberg, Heidelberg, Germany
The freezing of supercooled water droplets freely falling through a mixed-phase clouds is an ubiquitous natural process fundamental for the formation of precipitation. During the freezing of a droplet a solid ice shell grows from the outside inwards, leading to a pressure increase inside the liquid core, which can result in violent rupture of the ice shell and the production of secondary ice particles. To investigate this process of ice multiplication, the evolution of the droplets surface temperature during the second freezing stage was measured with a high-resolution infrared thermography system (INFRATEC). Drops of about 300 micrometer in diameter were levitated in an electrodynamic trap under controlled conditions with respect to temperature, humidity and ventilation. Combining experimental results and comprehensive process modelling, we explore the thermodynamic conditions beneficial for secondary ice production upon freezing of freely falling drizzle droplets.