Investigation of Ship-Induced Mesoscale Circulation Mechanics and Plume Spreading Rates

In previous modeling studies of ship injections into precipitating stratocumulus, a strong mesoscale circulation develops within the perturbed aerosol region. This circulation is thought to be the main reason for faster ship plume spreading in comparison to non-precipitating boundary layers and is theorized to arise in response to drizzle suppression in the ship plume. In this study, we explore the degree to which differences in precipitation, entrainment, and radiation between the environment and the ship track influence the development and intensity of the mesoscale circulation. Large-eddy simulations of both shallow and transitioning (stratocumulus-to-cumulus) precipitating boundary layers are used to test the importance of each ship-track-modulating mechanism by applying the environmental cloud number concentration to the ship track auto conversion and accretion tendencies (precipitation mechanism), cloud droplet sedimentation rates (entrainment mechanism), and effective radius calculations (radiation mechanism). Additionally, we analyze relationships between various boundary layer quantities and plume spreading rates to better understand the role of mesoscale circulations and the drivers of fast plume spreading environments.