Atmospheric aging effects on aerosol ice nucleation

Atmospheric ice-nucleating particles (INPs) play a crucial role in the climate system of the Earth, with their physicochemical properties strongly impacting their ice-nucleating activities (INA). These physicochemical properties of INPs can be profoundly altered by atmospheric aging processes. This article summarizes previous laboratory studies and field observations discussing the variation of INA impacted by atmospheric aging, including chemical modification, aging in water or aqueous solutions, changing of mixing state and morphology, and special aging pathways relevant to biological INPs. The inconsistencies between laboratory findings and field observations suggest that innovative ice-nucleating mechanisms need to be proposed to bridge datasets across different measurements. Furthermore, laboratory and field measurements of aged INPs could refine INP parameterization in climate models. Lastly, we present key perspectives of INA that merit further research and examination, especially including aging processes that involve multiple phases, complex morphology, or under upper tropospheric conditions, as well as poorly characterized biological INPs and anthropogenic aerosols. These research directions will help advance the overall predictability of INPs in model simulations and improve critical understanding of the climatic effect of atmospheric aerosols.