Peter A. Alpert
Paul Scherrer Institute, Switzerland
Title: A holistic and theoretically based sea spray aerosol ice nucleation model
Abstract: Sea spray aerosol (SSA) is a widely recognized important source of ice-nucleating particles (INPs) in the atmosphere. However, composition-specific identification, nucleation processes, and ice nucleation rates of SSA-INPs have not been well constrained. Direct X-ray microscopic and spectroscopic evidence of single ice nucleating particles is presented here and demonstrates that the exudates of marine microorganisms living in surface ocean waters are the organic matter source associated with sea spray aerosol. Then, the representation of sea spray aerosol induced ice nucleation is simplified, with the finding that all sea spray particles are ice nucleating particles, regardless of whether or not they were derived from seawater with high or low levels of microbial activity. A streamlined method will be presented to predict freezing from sea spray aerosol particles for immersion, deposition and homogeneous ice nucleation by extending our stochastic freezing model routed in ice nucleation theory to include results from our studies as well as those from previous studies. This is highly advantageous, since it does not require knowledge of the composition of the numerous types of solutes present in sea spray aerosol. In validation of our approach, we find that predicted ice nucleating particle concentrations are in agreement with previous ambient measurements performed under water-saturated conditions during a variety of field campaigns.
Technion - Israel Institute of Technology, Israel
Title: Marine bioaerosols: emissions, long range transport, pathogenicity, and possible ice nucleation potential
Abstract: Airborne microorganisms, also termed bioaerosols, constitute a diverse array of microbes capable of traversing continents and reaching high altitudes. The atmosphere serves as a key vector for their dispersal across distant ecosystems and habitats. Additionally, it also serves as a hub for bioaerosols to influence global cycles such as the water cycle through serving as ice nucleation nuclei. However, the characterization of such impacts is still at early stages, and further investigation is needed to comprehend their contributions to atmospheric processes, ecological systems, and health. In this presentation, I will present our recent findings on airborne marine microbial community, acquired through extensive long-range surveys across oceans. I will further describe the documentation of an aerial infection mechanism of oceanic blooms, and the possible involvement of the surface microlayer in their emission. Furthermore, I will elaborate on the possible contribution of these microbes to ice nucleation. These studies provide a window to the marine bioaerosol research field, advancing our understanding of how microbial communities impact the marine environment.
National Institute of Polar Research, Japan
Title: Possible factors influencing the variation of atmospheric ice nucleating particles in the Arctic lower troposphere
Abstract: Mixed-phase clouds, comprising both supercooled liquid droplets and ice crystals, occur with high frequency in the lower troposphere over the Arctic region. The microphysics of Arctic mixed-phase clouds is thought to be highly sensitive to the presence of aerosols capable of nucleating ice (i.e., ice nucleating particles (INPs)). However, the amount, variation, and source of INPs in the Arctic region remain poorly understood due to lack of the field INP data. In this presentation, I introduce recent findings derived from field measurements of atmospheric INPs at various locations in the Arctic (e.g., Svalbard, Bering/Chukchi Seas). I will also discuss possible factors influencing the variation of INPs in the Arctic lower troposphere.