Berlin 2014 – scientific programme

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UP: Fachverband Umweltphysik

UP 12: Atmosphäre - Labor

UP 12.5: Invited Talk

Thursday, March 20, 2014, 11:15–11:45, MAG 100

Contact freezing induced by mineral dust particles — •Nadine Hoffmann, Manfred Schäfer, Denis Duft, Alexei Kiselev, and Thomas Leisner — IMK-AAF, KIT, Karlsruhe, Germany

The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. In our experiment we study single water droplets freely levitated in an Electrodynamic Balance [2]. We have shown previously that the rate of freezing at given temperature is governed only by the rate of droplet-particle collision and by the properties of the contact ice nuclei [2, 3]. Recently, we have extended our experiments to potassium reach feldspar (Microcline), being one of the most abundant components of the atmospheric mineral dust particles [4]. We have dispersed feldspar particles from the water suspension and as dry powder and compared their freezing properties. In this presentation we will present these results and discuss their possible implication for elucidation of contact freezing mechanism.

[1] Ladino et al., Atmos. Chem. Phys., 13, doi:10.5194/acpd-13-7811-2013, 2013. [2] Hoffmann et al., Atmos. Meas. Tech., doi:10.5194/amtd-6-3407-2013, 2013. [3] Hoffmann et al., Faraday Discuss., doi: 10.1039/C3FD00033H, 2013. [4] Atkinson et al., Nature, 498, doi:10.1038/nature12278, 2013.