Data from recent field studies in the northeast and southeast Pacific are used to investigate pockets of open cells (POCs) that are embedded in otherwise uniform stratocumulus. The cellular structure within a POC resembles broader regions of open cellular convection typically found further offshore. In both regions, cells are composed of precipitating cell walls and cell interiors with depleted cloud water and even clearing. POCs are long lived and embedded in broader regions of stratocumulus where average droplet sizes are relatively large. In contrast, stratiform, or unbroken, cloud formations tend to be accompanied by less, or no, drizzle, suggesting that precipitation is necessary for the sustenance of the open cellular structure. Because, by definition, open cells are associated with a reduction in cloud cover these observations provide direct evidence of a connection between cloudiness and precipitation—a linchpin of hypotheses that posit a connection between changes in the atmospheric aerosol and climate.

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Department of Atmospheric Sciences, University of California, Los Angeles, Los Angeles, California

Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming

Department of Atmospheric Sciences, University of Washington, Seattle, Washington

Institute of Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands

Atmospheric Sciences Programme, University of British Columbia, Vancouver, British Columbia, Canada

National Center for Atmospheric Research, Boulder, Colorado