BIO-ICE: Connecting biological aerosol particles to ice nucleation

• Applicant: Dr. Markus Hartmann
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568271317

Ice nucleating particles (INPs), particularly INPs of biological origin (bio-INPs), play a crucial role in cloud microphysics by influencing ice formation, precipitation, and cloud lifetime. While it is known that ice nucleation at temperatures above -15°C is dominated by bio-INPs, it often remains elusive to establish a clear link between the measurements of bio-INPs and primary biological aerosol particles (PBAP; e.g., pollen and spores) in field measurements. In addition, systematic studies of the vertical distribution of INPs in general, and bio-INPs in particular, are scarce. As a consequence, current atmospheric models may underestimate the role of bio-INPs, leading to inaccuracies in precipitation and climate predictions. This project aims to fill these knowledge gaps by combining co-located INP measurements at different scales with real-time bioaerosol detection and identification. INP measurements will be performed on a seasonal time scale (at least 15 months of 24h samples), supplemented by short intensive sampling periods with vertical balloon-borne sampling and high temporal resolution sampling (5 min samples every hour). All INP samples will be analyzed for their fraction of bio-INPs. The INP and bio-INP measurements on a seasonal scale aim at investigating correlations with PBAPs in general or specific pollen and spores. The vertical and high temporal resolution measurements allow to relate (bio)-INP to the meteorological situation. For bioaerosol detection and identification, the Poleno Jupiter (Swisens, Switzerland), a new state-of-the-art bioaerosol monitor that combines ultraviolet laser-induced fluorescence (LIF), polarization and digital holography on a single particle basis, will be used. The Poleno Jupiter will be thoroughly characterized and the AI-driven bioaerosol identification will be extended with particle types relevant for the measurement site, i.e. primarily pollen of local anemophile plants. Bioaerosol identification will be verified against established methods such as manual pollen and spore counting of samples collected with a Hirst-type pollen trap and multispectral imaging flow cytometry. By using state-of-the-art detection techniques and high-resolution and long-term sampling strategies, this project will improve our understanding of bio-INP and their potential impact on cloud formation. The results will contribute to improved parameterizations of cloud microphysics in atmospheric models, leading to more accurate predictions of precipitation patterns and climate evolution in a warming world.

• DFG Programme: Research Grants
• International Connection: Austria, Switzerland
• Cooperation Partner: Dr. Fiona Tummon
• Co-Investigators: Dr. Julia Burkart; Dr. Susanne Dunker