ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-23589-2009 On the transitions in marine boundary layer cloudiness Sandu I. 1 Stevens B. 1 2 Pincus R. 3 Max Planck Institute for Meteorology, Hamburg, Germany University of California at Los Angeles, Los Angeles, California, USA University of Colorado/NOAA Earth System Research Lab, Boulder, Colorado, USA 05 11 2009 9 6 23589 23622 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/23589/2009/acpd-9-23589-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/23589/2009/acpd-9-23589-2009.pdf

Satellite observations and meteorological reanalysis are used to examine the transition from unbroken sheets of stratocumulus to fields of scattered cumulus, and the processes controlling them, in four subtropical ocean basins. A Lagrangian analysis suggests that both the transition, defined as the temporal evolution in cloudiness, and the processes driving the transition, are quite similar among the oceanic basins. The transitions in marine boundary layer cloudiness are an extremely persistent feature of the subtropical ocean's environment, so that the transitions' characteristics obtained by documenting the flow of thousands of individual air masses are well reproduced by the mean (or climatological) fields of the different data sets. This opens new opportunities for future observations and modeling studies of these transitions.

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