The Decay of Small Temperature Perturbations by Thermal Radiation in the Atmosphere

Abstract

It is assumed that a small temperature perturbation is superimposed on a steady equilibrium temperature distribution in the atmosphere. The time dependent equation for radiative transfer in a plane parallel gray atmosphere is then obtained in a manner following Spiegel (1957) and is extended to the case of line and band absorption. The result shows that the strong absorption regions at the line centers play an important role in radiative damping when the perturbed layer is thin, and that the weak absorption regions between lines becomes important with increasing thickness of the perturbed layer. It is shown that vertical temperature irregularities generated by adiabatic motion or advection may be smoothed by thermal radiation and the dissipation of these irregularities by radiative processes is comparable to vertical mixing by turbulence, if the scale of the perturbation is large.