Cloud Ice Processes Enhance Spatial Scales of Organization in Arctic Stratocumulus

Abstract

Stratocumulus clouds around the globe tend to organize into cellular patterns, a phenomenon that has been primarily studied for the subtropical trade wind region. However, stratocumulus are also prevalent in high latitudes, where they often occur as mixed-phase clouds. Yet little research has been conducted regarding mechanisms of cloud organization in the mixed-phase regime. In cloud-resolving model simulations we investigate the processes driving organization in open-cell mixed-phase stratocumuli. Similar to warm-phase clouds, mixed-phase clouds develop a subcloud circulation of evaporated/sublimated precipitation, cold pool formation, and consecutive updrafts driving new convective cells. For a larger ice to liquid water ratio, we find locally stronger precipitation and larger cloud cells. Hence, a higher concentration of ice nucleating particles can induce a breakup of the stratocumulus organization, with implications for the radiative balance at the surface. A decrease in cloud condensation nuclei concentration is also found to intensify precipitation and impact cloud organization.