On the Role of Aerosol for Mesoscale Moisture Aggregation and Trade Cumulus Organization in Early and Late 21st Century Conditions

Trade cumulus clouds aggregate moisture on the mesoscale, which in turn brings about mesoscale cloud organization. Moisture aggregation is driven by gross moist instability even without precipitation, but latent heating associated with enhanced (diminished) precipitation increases (reduces) gross moist instability. We hypothesize that this renders trade cumulus moisture aggregation and organization on the mesoscale susceptible to aerosol. We investigate this hypothesis using large eddy simulations of trade cumulus clouds in the Caribbean that organize into the "Flower" cloud state. Multi-day simulations on a 200 km domain (dx = dy = 100 m, dz = 50 m, dt = 2 s) with different initial aerosol concentrations, are analyzed. The susceptibility of mesoscale moisture aggregation and cloud organization to aerosol in early and late 21st century conditions is presented.