Marine Stratocumulus Cloud Clearing Episodes Observed during FIRE

Abstract

Data from the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) were combined with NOAA synoptic products, satellite imagery, and boundary-layer model data to document the existence and causes of periodic clearing of large regions of marine stratocumulus clouds off the coast of California during the summer season. These synoptic-to-mesoscale clearing episodes appear to be correlated with the ridging of the Pacific subtropical anticyclone into the United States Pacific Northwest, resulting in offshore flow effects. Furthermore, the subsidence associated with the Pacific subtropical anticyclone may help cause the clearing episodes, or prevent the redevelopment of these clouds in the clear regions. Because of the contribution of marine stratocumulus clouds to the global albedo, the clearing of large regions of these clouds may impact climate. Therefore, better understanding of these clouds is necessary in order to parameterize them in global climate models.