Optimal excitation of neutral Rossby waves

Properly configured disturbances are known to be effective in transferring the kinetic energy of a mean shear slow to neutrally stable modal and nonmodal waves Consideration of perturbation energetics requires that such oriented against the mean shear. Initial conditions chosen arbitrarily, except that they satisfy this requirement, have been shown to result in robust excitation of neutral waves. A question naturally arising from such studies is whether these exists, in some well-defined sense, a best most effective choice of initial conditions which optimally excites the waves. This questions addressed as a variation problem, and examples of optimal initial conditions are identified for the barotropic B-plane channel. These examples include the most effective excitation of a given neutral Rossby mode and the most rapidly growing perturbation for a given time period without restriction on spectral composition.