Giant aerosols increase precipitation in marine cumulus and stratocumulus clouds

Sea-salt aerosols with radii exceeding 1 μm have been observed over the oceans. Cloud droplets formed on these giant aerosols can quickly grow to drizzle sizes through condensation of water vapor. Therefore giant aerosols, although not numerous, have been speculated to increase the amount of precipitation produced in clouds. Testing this hypothesis in LES simulations has been difficult, because Eulerian microphysics models are not well suited to model growth of droplets on giant aerosols. On the contrary, Lagrangian microphysics models, which are an emerging alternative to the Eulerian bin microphysics models, can model giant aerosols in a straightforward manner.

LES simulations performed using the University of Warsaw Lagrangian Cloud Model (UWLCM) will be presented. In UWLCM, the Lagrangian super-droplet microphysics model is used. We will assess how giant aerosols affect precipitation formation in marine cumulus (setup based on the RICO campaign) and stratocumulus clouds (setup based on the research flight 2 of the DYCOMS campaign). It will be discussed how the impact of giant aerosols changes with the concentrations of giant and regular aerosols. The results are of importance also for cloud seeding experiments, in which giant sea-salt aerosols can be released into a cloud.