Boundary layer, cloud, and drizzle variability in the southeast Pacific stratocumulus regime

During the past five years a series of research cruises headed by NOAA ETL in the areas of the southeast Pacific stratocumulus regimes have provided unprecedented observations of boundary layer, cloud, and drizzle structures over an area largely unexplored previously. These cruises started with the EPIC 2001 field experiment followed by cruises in a similar area in 2003 and 2004. The sampling from these three cruises provides a sufficient data set to study the variability occurring over this region. This paper will compare observations from the 2004 cruise with published results from the other two cruises. Observations on the ship provide information about boundary layer structure, fractional cloudiness, cloud depth, liquid water path, and drizzle characteristics. Our initial evaluation indicates more strongly decoupled boundary layers during the 2004 cruise than the well-mixed conditions that dominated the cloud and boundary layer structures observed during the EPIC cruise. Diurnal forcing, synoptic conditions, and aerosol effects are being considered as factors affecting these variations.