ADJOINT PERTURBATION METHOD APPLIED TO 2-STREAM RADIATIVE-TRANSFER

This paper describes a computationally efficient method for solving th e plane parallel equation of radiative transfer for the two-stream flu xes based on the adjoint perturbation formulation. Analytical results for the perturbed fluxes are presented for a single layer atmosphere c ontaining both solar and thermal sources. Simple linear and exponentia l corrections to the base state fluxes are explored. For the solar rad iative transfer problem, the exponential form of the perturbation corr ection can accommodate deviations exceeding 400% in the base state opt ical properties while maintaining accuracy to within a few percent. Fo r thermal radiative transfer, the linear form of perturbation relation is the more accurate, but unlike the solar problem, deviations from t he base state optical properties must remain relatively small (less th an 20%) if the errors in the computed fluxes are to remain within a fe w percent of the true fluxes. The method is applied to the calculation of broadband solar fluxes in a layer of scatterers embedded in an abs orbing gas, where the absorption is modeled via the k-distribution met hod. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.