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UP: Fachverband Umweltphysik

UP 9: Aerosols

UP 9.2: Vortrag

Donnerstag, 19. März 2020, 14:20–14:40, HSZ 105

Heterogeneous ice nucleation on positively and negatively charged nanoparticles at mesospheric conditions - laboratory experiments — •Demetrius Ramette¹, Denis Duft¹, Thomas Dresch², and Thomas Leisner^1,2 — ¹IMK-AAF, Karlsruhe Institute of Technology, Germany — ²IUP, University of Heidelberg, Germany

Polar Mesospheric Clouds (PMCs) form at the polar summer mesopause in a cold and supersaturated environment and could serve as tracers for mesospheric processes and variability. PMC ice particles are presumed to grow on nanometre-size Meteoric Smoke Particles (MSPs). Rocket-borne measurements have shown that during polar summer, a significant fraction of mesospheric MSPs is positively charged. Therefore, studying heterogeneous ice nucleation on charged MSPs is of particular interest. We have developed an experimental setup for generating and trapping charged nanometre-size particles at mesospheric temperatures and adjustable water vapour supersaturation. These nanoparticles are composed e.g. of iron oxide Fe2O3 or silica SiO2 and serve as MSP analogues. Ice growth rates and ice nucleation onset conditions can be determined by measuring the particle mass as a function of residence time. Previous experiments performed on positively charged particles showed that the particle charge leads to an enhancement of particle growth for particles with a radius less than 3 nm. This contribution will show new experimental results, comparing the growth behaviour and critical saturation of positively and negatively charged nanoparticles.