How Cloud Phase Influences Aerosol Susceptibility

Aerosol susceptibility (AS) of clouds refers to their sensitivity to increases in condensation nuclei (CN) concentration. This study investigates AS in marine boundary layer clouds that occur during cold-air outbreaks, where ice particles are often present. In warm clouds, the AS of cloud albedo (precipitation) remains positive (negative); however, this sensitivity weakens as CN concentration increases. In mixed-phase clouds, AS becomes less pronounced and does not follow a consistent trend due to the positive response of snow growth to rising CN levels. Aside from microphysical responses, cloud fraction -- a macro-physical feature -- also shows susceptibility to aerosol effects. As CN increases, cloud fraction tends to decrease, which can mitigate up to one-third of the cloud albedo AS in warm clouds and three-fourths in mixed-phase clouds.