Influence of particle size on the ice nucleating ability of mineral dusts ETH Zurich, Institute for Atmospheric and Climate Science, Switzerland
Received: 06 February 2009 – Published in Atmos. Chem. Phys. Discuss.: 16 March 2009 Abstract. The recently developed Zurich Ice Nucleation Chamber (ZINC) was used to
explore ice nucleation of size-selected mineral dust particles at
temperatures between −20°C and −55°C. Four different
mineral dust species have been tested: montmorillonite, kaolinite, illite and
Arizona test dust (ATD). The selected particle diameters are 100 nm,
200 nm, 400 nm and 800 nm. Relative humidities with
respect to ice (RHi) required to activate 1% of the dust particles as
ice nuclei (IN) are reported as a function of temperature. An explicit size
dependence of the ice formation efficiency has been observed for all dust
types. 800 nm particles required the lowest RHi to activate.
Deposition nucleation below water saturation was found only below
−30°C or −35°C dependent on particle size. Minimum RHi
for 1% activation were 105% for illite, kaolinite and montmorillonite at
−40°C, respectively 110% for ATD at −45°C. In addition, a
possible parameterisation for the measured activation spectra is proposed,
which could be used in modeling studies.
Revised: 13 July 2009 – Accepted: 30 August 2009 – Published: 16 September 2009
Citation: Welti, A., Lüönd, F., Stetzer, O., and Lohmann, U.: Influence of particle size on the ice nucleating ability of mineral dusts, Atmos. Chem. Phys., 9, 6705-6715, doi:10.5194/acp-9-6705-2009, 2009.