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Observations of Natural Variability in Marine Stratocumulus Clouds

Albrecht, Bruce University of Miami
Kollias, Pavlos RSMAS/University of Miami
Jo, Ieng Rosentiel School of Marine & Atmospheric Science
Ghate, Virendra RSMAS/Univ. Miami
Serpetzoglou, Efthymious
Minnis, Patrick NASA Langley Research Center
Sun-Mack, Szedung SAIC

Large to mesoscale features affecting the albedo of marine stratocumulus clouds are observed frequently and can have a substantial impact on the overall albedo of the subtropical cloud decks. One such naturally occurring feature—defined as a cloud rift—is characterized as a large-scale, persistent area of broken, low reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. We review results from a recent study of a rift that show the microphysical characteristics in this feature to differ substantially from those in the surrounding solid stratocumulus. Cloud droplet concentrations were more than a factor of 2 lower than those in the solid cloud and CCN concentrations were found to be about 3 times greater in the solid cloud area compared with those in the rift. Although drizzle was observed near cloud top in parts of the solid stratus cloud, the largest drizzle rates were associated with the broken clouds within the rift area. Two cloud modes—one associated with typical marine air masses (solid cloud with little drizzle) and the other in CCN depleted (drizzle cleansed) areas within the rift--were observed. Further definition of the large to mesoscale natural variability in microphysical cloud properties of marine stratocumulus from ship-based remote and in situ observations off the west coast of South America will be presented. The potential for quantifying the natural variability in cloud characteristics at Pt. Reyes, California though the first deployment of the ARM Mobile Facility will be discussed. Satellite retrievals of Deff and other cloud properties from satellite observations for the period 2000-2004 will be used to examine the variability that will be expected at Pt. Reyes and the horizontal scale of the cloud features giving rise to the local variability.

This poster will be displayed at the ARM Science Team Meeting.