Atmospheric aerosols influence cloud formation and Earth's radiative balance by acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs). Among the diverse aerosol population, biological and biogenetic particles, including bacteria, fungal spores, pollen, plant debris, marine organic matter, and their molecular fragments, have emerged as disproportionately efficient nuclei, capable of initiating ice formation at temperatures far warmer than mineral dust or other inorganic aerosols. Despite growing recognition of their importance, the sources, atmospheric transport, transformation, and ice- or cloud-nucleating mechanisms of these particles remain incompletely understood, limiting their representation in cloud microphysics and climate models.

This session invites contributions that advance understanding of the origin, composition, and atmospheric processing of biological and biogenetic aerosols and their role as CCN and INPs. We welcome studies spanning laboratory investigations of nucleation mechanisms, field observations and sampling campaigns, novel detection and characterization techniques, and modeling efforts that quantify the climatic relevance of bio-aerosols across scales. Contributions addressing the coupling between terrestrial and marine ecosystems and atmospheric ice/cloud nucleation, as well as the impact of a changing climate and land use on bio-aerosol emissions, are particularly encouraged. By bringing together atmospheric scientists, microbiologists, and modelers, this session aims to foster interdisciplinary dialogue.