ON THE PRESSURE DEPENDENCE OF RADIATIVE HEAT TRANSFER IN THE ATMOSPHERE

Abstract

Recent experimental evidence seems to establish the validity of Lorentz (linear) pressure broadening of spectral lines under atmospheric conditions. This simplifies the analytical representation of the fractional transmission by atmospheric layers in which the pressure decreases with height. A transmission function is derived and tabulated, with use of the Elsasser assumption of lines of equal intensity and equal spacing. It is found that further approximations made in the construction of the Elsasser diagram result in overestimation of cooling rates with its use. Stratospheric heating and cooling rates caused by carbon dioxide are calculated for the N.A.C.A. Standard Atmosphere. Considerable radiative-flux divergence is found in the 15-µ band. Neglect of the pressure effect has resulted in underestimation of outgoing radiation by previous investigators of the heat balance. Thus a smaller value of the albedo is required, in agreement with Fritz's findings.