Freezing of water droplets colliding with kaolinite particles 1Department of Chemistry, Atmospheric Science, University of Gothenburg, 41296 Gothenburg, Sweden
2Copenhagen Centre for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 København Ø, Denmark
3EPFL STI IMT LOA, Station 17, 1015 Lausanne, Switzerland
Received: 19 Nov 2008 – Published in Atmos. Chem. Phys. Discuss.: 27 Jan 2009 – Published: 03 Jul 2009Abstract. Contact freezing of single supercooled water droplets colliding with
kaolinite dust particles has been investigated. The experiments were
performed with droplets levitated in an electrodynamic balance at
temperatures from 240 to 268 K. Under relatively dry conditions
(when no water vapor was added) freezing was observed
to occur below 249 K, while a freezing threshold of 267 K was observed when water vapor was added
to the air in the chamber.
The effect of relative humidity is attributed to an
influence on the contact freezing process for the kaolinite-water droplet
system, and it is not related to the lifetime of the droplets in the
electrodynamic balance. Freezing probabilities per collision were derived
assuming that collisions at the lowest temperature employed had a probability
of unity. Mechanisms for contact freezing are briefly discussed.
Citation: Svensson, E. A., Delval, C., von Hessberg, P., Johnson, M. S., and Pettersson, J. B. C.: Freezing of water droplets colliding with kaolinite particles, Atmos. Chem. Phys., 9, 4295-4300, doi:10.5194/acp-9-4295-2009, 2009.