Quantifying scavenging efficiencies of different aerosol species and size-resolved volume concentrations in tropical convective clouds over the West Pacific

While past work quantified aerosol scavenging efficiencies (SEs) in midlatitude mixed-phase deep convection, SEs are less well known for shallower convection. We used aircraft data over the tropical west Pacific to calculate SEs for three marine cumuli of different top heights (3–7 km MSL) using a simple entrainment model and measurements of the cloud outflow and nearby clear air.

Across cases, efficient scavenging was observed for sulfate (>86%) and black carbon (70%–80%), while organic aerosols (53%–60%) and nitrate (61.5%) were moderately scavenged. Ammonium had a wide SE range (53%–87%). SEs of aerosol volume concentration showed near-total removal of aerosols with diameters greater than 100 nm (>92%) and inefficient removal for aerosols with diameters less than 100 nm (30%–50%), associated with the preferential activation and removal of larger particles.