STRUCTURE, ENERGETICS AND PROPAGATION OF ROTATING CONVECTIVE STORMS. PART I: ENERGY EXCHANGE WITH THE MEAN FLOW.

Abstract

A three-dimensional buoyant convective element responds to the existence of mean vertical shear by developing rotation about a vertical axis, with the rotational kinetic energy abstracted from that of the mean flow. This process is illustrated with the aid of linear analysis. From consideration of nonlinear processes it is concluded that a portion of the rotational energy is transformed into that of the overturning velocity field, thus enhancing further buoyant energy release. The storm structure which is optimal for energy transfer from the mean flow to rotational disturbances is a single updraft propagating with the mean flow and with counter-rotating vortices on both sides. The transfer of energy from rotational to overturning modes is, however, optimized by laterally propagating updrafts with coincident vortices.