From lab to field: examining immersion freezing of atmospheric relevant ice nucleating particles

• Applicant: Dr. Heike Wex
• Subject Area: Atmospheric Science
• Term: from 2011 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 170852269

The project suggested here, in RP6 of INUIT-2, aims at adding fundamental understanding to the workings of heterogeneous ice nucleation, and especially to the role of biological and mixed mineral-biological ice nucleating particles (INP) therein. The Leipzig Aerosol Cloud Interaction Simulator (LACIS) will be used to investigate the immersion freezing behaviour of a suite of different INP, including biological (fungal) and mixed biological-mineral INP, among them atmospherically relevant materials like soil dusts and INUIT-2 test samples. For the latter, results gained by different groups, from within and outside of INUIT, will be intercompared, as it had been successfully done in INUIT-1 using simpler test INP. For the INP proposed for examination in RP6 wherever meaningful and feasible, surface treatments such as coatings with reactive and nonreactive substances will be applied, and their influence of the particles to act as INP will be examined. As documented in earlier studies at LACIS, controlled surface treatments are an excellent tool for determining what it is that makes a particle an effective INP. Furthermore they allow for the elucidation of the effects of aging on INP. It is also planned to extend our measurements towards water sub-saturated conditions, in order to examine under which conditions the observed heterogeneous ice nucleation is due to the immersion freezing of concentrated solutions or deposition ice nucleation. From the experimental data gained, different parameterizations, both time dependent and time independent, will be derived and offered to the community for further use in modelling studies. The here proposed studies will significantly add to and complement the very successful works performed at LACIS during INUIT-1, which had focused more strongly on pure mineral dusts and pure biological particles. The examination of more complex and hence more atmospherically relevant INP will significantly contribute to understanding and quantifying atmospheric ice nucleation in general and the relative contributions of mineral and biological substances to atmospheric ice nucleation in particular.

• DFG Programme: Research Units
• Subproject of: FOR 1525: INUIT - Ice Nuclei Research Unit