PHYSICOCHEMICAL PROPERTIES OF ATMOSPHERIC AEROSOLS AND THEIR EFFECT ON ICE CLOUD FORMATION

Abstract

Atmospheric aerosols play a vital role in the Earth's energy budget-directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation nuclei and ice-nucleating particles [1, 2]. The cloud formation potential of aerosol is driven by multiple factors, including surface properties, size distribution, composition, mixing state, phase state, and morphology [3]. The interaction of aerosols with clouds alters the aerosol's physicochemical properties. Those properties can also evolve during transport due to atmospheric processing, in turn, affect the aerosol's ice nucleation and cloud formation activities. This thesis presents experimental studies to understand the role of physicochemical properties of aerosol on the formation of ice. To get a detailed understanding of the aerosol effect on ice nucleation, we conducted controlled ice nucleation experiments on a known surface (muscovite mica) with controlled properties (e.g., surface cations) as well as ice nucleation experiments on complex atmospheric particles, which were characterized with multimodal microspectroscopic techniques. The results from controlled experiments suggest that the ice nucleation activity of a surface can be modified by simply changing the surface cations. In contrast, ice nucleation experiments with complex atmospheric particles indicates a more complicated dependence on the physicochemical properties.