Excitation of Planetary Rossby Waves in the Winter Stratosphere by Periodic Forcing

Abstract

A theoretical examination is made of the dynamics of transient planetary Rossby waves in the winter stratosphere forced from below, using the quasi-geostrophic, mid-latitude β-plane approximations. The response of planetary Rossby waves to a periodic forcing in the lower atmosphere is described in a model as a function of three parameters: the intensity of mean zonal wind, the wavelength of disturbance, and the period of excitation. It was found that the maximum response of the wave should take place according to the steady-state solution for a certain ratio of the wavelength to the excitation period.
Periodic changes of the mean zonal wind intensity were assumed to be a source of the wave excitation and numerical time integrations of the linearized potential vorticity equation were carried out. In the present model, the results obtained agree well with the time-dependent behavior of planetary Rossby waves observed in the stratosphere during winter.