The Increase or Decrease of Mean-Flow Energy in Large-Scale Horizontal Flow in the Atmosphere

The transfer of energy between mean flow and disturbance for a barotropic non-divergent fluid is investigated by solution of the vorticity equation to obtain initial tendencies corresponding to assigned flow-patterns. The initial rate and direction of energy transfer are computed for different types of mean flow and disturbance. These calculations suggest that the form, as well as the wavelength, of the disturbance is a controlling factor in determining the initial energy-transfer, and that conclusive inferences cannot be made merely from the character of the mean flow. The distribution of initial changes in mean flow is calculated in several cases; it is found that, for both initially amplified and initially damped disturbances, momentum may be transferred from both sides into a central zone of maximum mean flow.