Radiative Damping and Amplitude of Long-Wavelength Modes in the Stratosphere

Abstract

The dependence of radiative damping rates in the stratosphere is investigated as a function of the distribution of active radiative gases and the wavelength of the temperature perturbation. Damping rates are found to depend considerably on the scale of the temperature perturbation. The same radiative model used to calculate damping rates is employed to study the effects of more accurate radiative calculations on the amplitude of long-wavelength Green modes in the stratosphere. A quasi-geostrophic ?-plane model is used for this purpose and the results show a quite large reduction of the amplitudes of the modes up to wavenumber 3. These results are qualitatively discussed by taking into account a nonlinear damping mechanism and the dependence of the Newtonian cooling coefficient on the scale of the temperature perturbation.