The thermal excitation of atmospheric oscillations

The excitation by thermal action of large-scale oscillations in an atmosphere on a rotating globe is discussed, The temperature of the atmosphere varies in an arbitrary manner with height. The treatment follows the same lines as that given by Pekeris for gravitationally excited oscillations, and the results are expressed in terms of an 'equivalent gravitational oscillation'. Some numerical results are given for the case of the solar semi-diurnal oscillation and are found not to conflict with the hypothesis, put forward by Chapman in 1924, that the thermal and gravitational contributions to this oscillation are of the same order of magnitude.