Comprehensive process studies of heterogeneous ice nucleation: from single cloud droplets to cloud simulations.

• Applicant: Dr. Ottmar Möhler
• Subject Area: Atmospheric Science
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 170852269

Reliable weather predictions and climate change projections require a sound understanding of the ice formation in tropospheric clouds, in particular the so-called heterogeneous ice nucleation which involves solid atmospheric aerosol particles. This project aims at a comprehensive investigation of heterogeneous ice nucleation of relevance for mixed-phase and cirrus clouds in concert with 8 other research projects within the research unit INUIT. Ice formation in the contact freezing mode will be investigated for single levitated droplets in electrodynamic levitators (Paul trap). The existing cloud chamber AIDA and, if availa-ble in 2016 as planned, the new dynamically controlled cloud chamber AIDA-2 will be used for investigat-ing the effect of aerosols on immersion freezing, contact freezing and deposition nucleation modes. Major objectives are (1) to investigate the immersion freezing, deposition nucleation and contact freezing properties of the lNUlT-2 reference aerosols in close cooperation with all INUIT partners, (2) to perfonm AIDA cloud simulation experiments on the IN behaviour of re-dispersed atmospheric aerosol samples in cooperation with RPS, (3) to perform AIDA experiments with porous aerosols in order to elucidate pre-activation, capillary condensation freezing and deposition nucleation mechanisms, (4) to perform levitated droplet contact nucleation experiments with mixed and aged aerosols, (5) to elucidate fundamental processes and mechanisms of contact nucleation, (6) to develop, in close collaboration with RP3 and RP5, a comprehensive and consistent parameterisation framework for the fonmulation of primary ice fonmation in models, (7) to plan and conduct first cloud chamber contact freezing experiments taking advantage of the combined expertise with levitated droplet and cloud simulation chamber activities, and (8) to conduct two larger field instrument and laboratory method inter-comparison campaigns at the AIDA facility, one for the INUIT teams and one with international partners, in order to develop and document high international standards of ice nucleation and ice nucleating particle research. DFG form 54.011 - 04/14 page 4 of 8 These AIDA cloud chamber activities will provide strong links between the laboratory, field and modelling projects of INUlT-2. In extension to the ongoing INUIT project, we will investigate ice nucleation properties of porous particles, immersion freezing and deposition nucleation of sizeselected aerosol particles with diameters up to a few microns, quantify contact freezing effipiencies of atmospherically relevant complex INPs, and conduct cloud simulation experiment on contact freezing. We will also suppori the development and installation of a new data base system for laboratory results of heterogeneous ice nucleation.

• DFG Programme: Research Units
• Subproject of: FOR 1525: INUIT - Ice Nuclei Research Unit
• Co-Investigators: Dr. Alexei Kiselev; Professor Dr. Thomas Leisner