Cloud processing dominates the vertical profiles of aerosols in marine air masses over the Great Barrier Reef

Kurzfassung

The cloud condensation nuclei (CCN) concentrations greatly determine the vertical microphysical evolution and rain initiation of warm convective clouds. We investigated the vertical profile of aerosol particles large enough (diameter > 60 nm) to act as CCN in marine air masses over the Great Barrier Reef. Such data were collected during an aircraft research campaign in February 2024. The results show a strong relationship between the microphysical processes measured in the cloud and the aerosol properties measured at the same altitude. The number concentration of aerosol particles decreases significantly above cloud bases due to CCN activation into cloud droplets. For heights above the in-cloud rain initiation level, the aerosol concentrations decrease further due to the scavenging of particles by drizzle and raindrops. The Hoppel minimum in particle size distributions is observed up to the altitude at which the coagulation process intensifies. Furthermore, a tail of larger aerosol particles was measured above the altitudes of rain initiation. These results suggest that the vertical profile of aerosols measured in marine air masses is dominated by cloud processing.