The perturbation formulations presented in papers published by Box et al. have been investigated for homogeneous and real atmospheres by perturbing the optical thickness of an absorbing gas, with the emphasis in this paper on ozone changes. Both exponential and linear perturbation formulations were investigated for a model with plane parallel geometry and different solar zenith angles. The results for the exponential perturbation predictions for net surface fluxes were very good in all cases where the solar zenith angle was less than 60¿. However, where the solar zenith angle was increased past 60¿, the range of validity of the perturbation models was clearly reduced. Applications to action spectrum integrals are presented which show that the approach is able to provide good results for zenith angles up to 60¿, with accuracy past this angle being better than for nonintegrated effects.¿ 1997 American Geophysical Union