%0 Generic
%A Steinke, Isabelle
%D 2013
%F heidok:15967
%R 10.11588/heidok.00015967
%T Ice nucleation properties of mineral dusts
%U https://archiv.ub.uni-heidelberg.de/volltextserver/15967/
%X Ice nucleation in clouds has a significant impact on the global hydrological cycle as well as on the  radiative budget of the Earth. The AIDA cloud chamber was used to investigate the ice nucleation  efficiency of various atmospherically relevant mineral dusts. From experiments with Arizona Test Dust (ATD) a humidity and temperature dependent ice nucleation  active surface site density parameterization was developed to describe deposition nucleation  at temperatures above 220 K. Based on these results, a parameterization for deposition nucleation  initiated by desert dusts and clay minerals is proposed. The time dependence observed during the  deposition nucleation experiments with ATD seems to be relevant only at very small cooling rates.  Experiments with atmospherically relevant dust samples revealed large differences in the ice nucleation  efficiencies among the different dusts. Volcanic ash emitted during the Eyjafjallajökull  eruption in 2010 proved to be slightly less ice-active than mineral dust particles from desert areas.  In contrast, soil dust particles rich in organic matter and fossile diatomite were very ice-active particles.  For the soil dust particles, the soil organic matter is probably the reason for the enhanced  ice nucleation efficiency compared to desert dusts which is, however, most likely not directly determined  by viable organisms such as fungi or bacteria. Coatings with secondary organic compounds led to a significant deterioration of the ice nucleation  efficiency observed for fossil diatomite in the immersion freezing and the deposition nucleation  mode. Deposition mode nucleation initiated by mineral dust particles was suppressed by coatings  with sulfuric acid whereas there was no effect on the immersion freezing properties. The immersion freezing properties of several substrates used as ice nuclei substitutes were investigated  with a cold stage setup. Muscovite initiated heterogeneous ice nucleation at approximately  250 K but was much less ice-active than mineral dusts. Droplets placed on silicon wafers froze  only close to the homogeneous freezing threshold. The freezing properties of these silicon wafers  could be changed signicantly by modifying the wafer surface through adding regular structures  such as trenches which suggests that the surface morphology may have an influence on the ice  nucleation efficiencies of atmospheric particles.