A field study of nocturnal stratocumulus II Turbulence structure and entrainment

Tethered balloon‐borne instrumentation has been used to study the small‐scale air motion and temperature variations occurring within a layer of nocturnal stratocumulus. The observations indicate a very sharp and intermittently turbulent entrainment interfacial layer with some evidence for a characteristic entrainment scale of about 10m. Within the cloud layer convective motions are apparent and these take the form of cold, downward moving plumes which increase in scale away from cloud top. They are generated by the large radiative loss from the upper part of the cloud. Some statistical features of the turbulence field in cloud are discussed and compared with other observations from stratocumulus and the daytime convective boundary layer.