Observations of Marine Stratocumulus Clouds During FIRE

Abstract

During June and July 1987, a major collaborative experiment (part of The First ISCCP [International Satellite Cloud Climatology Project] Regional Experiment (FIRE) took place off the coast of California to study the extensive fields of stratocumulus clouds that are a persistent feature of subtropical marine boundary layers. For the first time, measurements were made on both the regional scale and on the detailed local scale to permit the widest possible interpretation of the mean, turbulent, microphysical, radiative, and chemical characteristics of stratocumulus, together with the interactions among these quantities that am believed to he important in controlling the structure and evolution of these clouds. Multiple aircraft were used to make detailed, in situ measurements and to provide a bridge between the microscale and features seen from satellites. Ground-based remote-sensing systems on San Nicolas Island captured the time evolution of the boundary-.layer structure during the three-week duration of the experiment, and probes flown from tethered balloons were used to measure turbulence at several levels simultaneously, and to collect cloud-microphysical data and cloud-radiative data. Excellent cloud conditions were present throughout the experiment, although the data show that even this relatively simple cloud system displays fairly complicated structures on a variety of scales. Overall, the operational goals of the experiment were satisfied and preliminary results lock very encouraging. The data collected should provide the observational base needed to increase our understanding of how stratocumulus clouds are generated, maintained, and dissipated, and thus provide for better parameterizations in large-scale numerical models and improved methods for retrieving cloud properties by satellite.