Observations of Diurnal Variation in a Cloud-capped Marine Boundary Layer

Observations are presented of the turbulent structure of a cloud-capped boundary layer during the 1987 FIRE marine stratocumulus project. The measurements were made from San Nicolas Island, off the coast of California, using instruments attached to the cable of a tethered balloon. A marked diurnal variation is demonstrated through a direct comparison of observations made around local noon and approximately 12 hours later. Emphasis is given to the decoupling of the boundary layer during the morning into a separate cloudy layer and surface mixed layer.