Discrete Space Theory of Radiative Transfer and its Application to Problems in Planetary Atmospheres

G. E. Hunt Science Research Council, Atlas Computer Laboratory, Chilton, Didcot, Berkshire, England

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I. P. Grant Science Research Council, Atlas Computer Laboratory, Chilton, Didcot, Berkshire, England

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Abstract

The classical methods that have been devised to analyze theoretically the transfer of radiation in plane parallel atmospheres may produce an analytic solution provided that the medium is assumed to be homogeneous. Even then, when the results have been expressed in terms of tabulated functions, practical computations are difficult and tedious. It is therefore essential to employ numerical methods for solving realistic radiative transfer problems.

We briefly describe a method of computation that uses discrete space techniques depending on concepts of invariance. The solution algorithms compute internal and external light fields for inhomogeneous plane parallel atmospheres with arbitrary internal, external source distributions and scattering diagrams. The stability and errors of our algorithms are susceptible to mathematical analysis and make it possible to identify the critical parameters in the calculation with precision.

To illustrate our techniques, we briefly discuss the practical problem of making theoretical predictions of the spectral properties of ice clouds at selected spectral intervals between 2.6–150 μ in the infrared. The predictions are consistent with recent measurements.

Abstract

The classical methods that have been devised to analyze theoretically the transfer of radiation in plane parallel atmospheres may produce an analytic solution provided that the medium is assumed to be homogeneous. Even then, when the results have been expressed in terms of tabulated functions, practical computations are difficult and tedious. It is therefore essential to employ numerical methods for solving realistic radiative transfer problems.

We briefly describe a method of computation that uses discrete space techniques depending on concepts of invariance. The solution algorithms compute internal and external light fields for inhomogeneous plane parallel atmospheres with arbitrary internal, external source distributions and scattering diagrams. The stability and errors of our algorithms are susceptible to mathematical analysis and make it possible to identify the critical parameters in the calculation with precision.

To illustrate our techniques, we briefly discuss the practical problem of making theoretical predictions of the spectral properties of ice clouds at selected spectral intervals between 2.6–150 μ in the infrared. The predictions are consistent with recent measurements.

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