Convective Motion in the Cumulus Subcloud Layer

Abstract

An observational study of convective motion in the cumulus subcloud layer was made by remote sensing from the ground. The vertical distributions of three-dimensional wind components are observed by a Doppler acoustic sounder (Sodar); the cloud base temperature is detected by a radiation thermometer; and cloud form was recorded by a fish-eye camera. Three cases of cumulus cloud passage were observed during the period of August and September 1981. In the case of a small developing cumulus cloud, an updraft in the boundary layer preceded the cloud passage. However, in the case of a little larger and more mature cloud, an updraft area trails from the cloud. This trailing updraft area consists of a horizontally rotating wind system in the boundary layer. In the case of a roll cloud, no systematic relation between cloud and boundary layer air flow was found. In all three cases no evidence of cloud passage was seen in the surface meteorological parameters.