Enhancement of cloud cover and suppression of nocturnal drizzle in stratocumulus polluted by haze

Abstract

Recent satellite observations indicate a significant decrease of cloud water in ship tracks, in contrast to an ensemble of in situ ship-track measurements showing no average change in cloud water relative to the surrounding clouds, and contrary to the expectation of cloud water increasing in polluted clouds. We find through large-eddy simulations of stratocumulus that the trend in the satellite data is likely an artifact of sampling only overcast clouds. The simulations instead show cloud cover increasing with droplet concentrations. The simulations also show that increases in cloud water from suppressing drizzle by increasing droplet concentrations are favored at night or at extremely low droplet concentrations.