LINE ABSORPTION AND RADIATIVE EQUILIBRIUM

Abstract

Radiative-equilibrium temperature distributions (e.t.d.'s) are derived for a line-absorbing atmosphere in which the absorption coefficients are given by the Lorentz collision-broadening formula. The line half-width is assumed strictly proportional to the pressure at all levels. The actual e.t.d. is approximated by a superposition of the e.t.d.'s of all the individual lines, with neglect of overlapping of the lines. The individual e.t.d.'s depend on the variation of mixing ratio and the position of the line relative to the black-body curve but, for strong lines, not on the line intensity. Upon comparison of the e.t.d.'s found with the standard atmosphere, conclusions are drawn about the contributions of various regions of the infrared spectrum to radiative cooling. It is found that the 6 µ water-vapor band plays a small role in radiative transfer above the lower troposphere. In the upper troposphere, the slopes of the e.t.d.'s are remarkably close to the standard atmosphere. Formal proofs are given that (a) any e.t.d. engenders convection near the earth's surface and (b) the isothermalcy of the stratosphere cannot be explained as an infrared e.t.d.