The Motion of Uneven Structure of Convective Clouds

Abstract

An observational study on the motion of the uneven structure on the surface of convective clouds is carried out using a lime-lapse video recorder. The development of the uneven structure shows that the mixing near the cloud-environmental interface occurs through outward motion of the projected part (turret) and inward motion of the depressed part, which are quite different from the winding billowlike motion. The theory presented here predicts the growth direction of the turret in its growing stage. Namely, two angles, one between a vertical line and the growing direction of the turret (=α) and the other between the normal to the mean cloud surface at the place of the turret and the growing direction of the turret (=?), are equal (α = ?). Nine turrets are selected from three cumuli to compare the observation with the prediction, and a reasonable result was obtained. Average values of 2α/(α + ?) and 2?/(α + ?) over the nine samples are 1.11 and 0.89, respectively, with the standard deviation 0.26.