Probing Boundary Layer and Cloud Structure in Open Cellular Stratocumulus over the Eastern North Atlantic

Marine stratocumulus clouds are an important piece of the global radiation balance though many questions surrounding their underlying physical and dynamical controls remain. The transition from closed to open cellular convection regimes has been studied in field campaigns as well as through modeling in classic stratocumulus regions. The mesoscale organization of marine low clouds alters the radiatively important spatial distributions of cloud fraction and liquid water path. However, aircraft studies are limited to providing a handful of case studies that make it difficult to draw more general conclusions and simulations require validation. The newest U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) site is well situated to provide unprecedented, continuous and extensive measurements of the marine boundary layer from its position in the Azores. Here, we employ more than two years of data from the ENA ARM Doppler Lidar coupled with ceilometer, microwave radiometer and radiosonde measurements to characterize boundary layer and cloud vertical motion and turbulence properties during open cell events. Cases are drawn from both mid-latitude air masses in cold air outbreaks and subtropical closed-to-open Sc transitions. Compiling observations from a permanent site provides a larger and more diverse sample than could be provided by typical aircraft campaigns, yielding more insight into common and anomalous behavior of open cell boundary layer and cloud dynamics.