Articles | Volume 10, issue 5
Atmos. Chem. Phys., 10, 2377–2391, 2010
Atmos. Chem. Phys., 10, 2377–2391, 2010

  08 Mar 2010

08 Mar 2010

On the transitions in marine boundary layer cloudiness

I. Sandu1, B. Stevens1,2, and R. Pincus3 I. Sandu et al.
  • 1Max Planck Institute for Meteorology, Hamburg, Germany
  • 2University of California at Los Angeles, Los Angeles, California, USA
  • 3University of Colorado/NOAA Earth System Research Lab, Boulder, Colorado, USA

Abstract. 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 oceans. 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 subtropical oceans. The increase in sea surface temperature and the associated decrease in lower tropospheric stability appear to play a far more important role in cloud evolution than other factors including changes in large scale divergence and upper tropospheric humidity. During the summer months, the transitions in marine boundary layer cloudiness appear so systematically that their 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 highlights interesting opportunities for future observational and modeling studies of these transitions.

Final-revised paper