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 (RH,) 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. 800nm particles required the lowest RH_i to activate. Deposition nucleation below water saturation was found only below -30°C or -35°C dependent on particle size. Minimum RH_i 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.
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