Environmental & Climate Sciences Department Seminar

The sources and nature of emissions of ice nucleating particles (INPs) to the atmosphere affect aerosol-cloud interactions, precipitation, and climate (via cloud phase and lifetime influences). There is a need to characterize INP emissions, categorized in some manner to define the most important classes over different regions and at different times. While past research has emphasized the global relevance of mineral dusts and other inorganic particles as atmospheric INPs, we highlight unique measurements identifying the most abundant and important classes of INPs in many regions as emanating from organic and biological sources. INPs whose actions are dominated by unresolved biological and organic materials are features not only of emissions from non-desert continental soils, but also marine emissions (via sea spray), from biomass burning, and from yet to be identified sources in the Arctic over large portions of the year. We will show, mostly using data from DOE ARM campaigns that INPs of organic and inorganic types may be amenable to relatively simple parameterizations for use in numerical modeling studies. However, strong needs remain for quantifying biological INPs that dominate ice nucleation in many regions in the cloud activation regime from 0 to 20°C (or lower). This will likely require targeted and novel measurements of both bioaerosols and INPs in field studies, a few examples of which will be introduced.