REGIONS OF VALIDITY OF VARIOUS ABSORPTION-COEFFICIENT APPROXIMATIONS

Abstract

Elsasser's integral for the absorption by a periodic line pattern is evaluated and used to examine the validity of various approximations concerning the absorption coefficient. It is found that composite absorption curves, obtained by ignoring overlapping for small optical paths and ignoring the pressure-dependent term in the denominator of the expression for the absorption coefficient for large optical paths, may be applicable to calculation of radiative heat transfer in the atmosphere. It is shown that the theoretical prediction of the ?square-root law? of absorption is based on use of approximations that are particularly invalid for the cases for which the ?law? is supposed to be valid. An explanation is given for the apparent experimental verification of this ?law?.