Mesoscale Organization in Cumulus-Coupled Marine Stratocumulus

Abstract

Marine stratocumulus clouds are the dominant cloud type in the mid-latitudes and exert major influences on the regional and global energy balance. Despite the importance of these clouds, most Global Circulation Models (GCMs) and Numerical Weather Prediction (NWP) models struggle to accurately portray their properties.  The marine stratocumulus cloud system in the mid-latitudes undergoes important morphological changes in response to increasing sea-surface temperatures toward the tropics including a critical transition from a single layer of cloud to increasingly broken cloud structure. A component of this transition is the “cumulus-coupled” stage in which cumulus clouds form beneath the existing stratocumulus layer and rise into it.  As this stage proceeds, these cumulus clouds often become organized into clusters referred to as marine boundary layer convective complexes (MBLCC).  Many physical processes operate in the cumulus-coupled environment, but it remains unclear how these processes play a role in the formation and life cycle of MBLCC.  This study, made possible by recent advances in observational capabilities and computing, will provide basic information about MBLCC that is heretofore lacking.  Multi-faceted observations combined with detailed modeling will answer basic questions regarding the number of MBLCC modes that exist over the Eastern North Atlantic and in other mid-latitude ocean regions and what physical processes lead to the organization of MBLCCs.