Upgrade of FASCODE and MODTRAN to Full Solar Capability Including Multiple Scattering and Spherical Geometry.
Abstract
The general objective of this report is to document and discuss an upgrade of the radiative transfer code MODTRAN to include rigorous multiple scattering. Progress on work aimed at a similar upgrade for the line byline code FASCODE will also be discussed. For MODTRAN the upgrade is accomplished by incorporating the DISORT (DiScrete Ordinate Radiative Transfer) multiple scattering program into MODTRAN, including proper interfaces, to allow for accurate computation of multiple scattering effects. The merging of MODTRAN and DISORT is greatly facilitated by the fact that MODTRAN is a quasimonochromatic code, since DISORT requires fixed frequency input. The heart of MODTRAN is a narrowband model that computes gaseous path transmittances from the HITRAN data base with wavenumber steps at 1/cm. Effective optical depths and appropriate particulate scattering parameters (also computed in the MODTRAN code) may then be input into the DISORT code which can do the complete radiative transfer computation including multiple scattering. However, the current version of DISORT is plane- parallel, whereas MODTRAN includes a geometry package that allows accurate computation of single scattering in spherical geometry. Therefore, the present implementation of DISORT into MODTRAN uses DISORT to compute only the multiple scattering component of the source function in much the same way that the present approximate multiple scattering treatments are used in MODTRAN. This approach facilitates the interfacing of DISORT with MODTRAN to provide a rigorous treatment of multiple scattering effects, and it requires only minor changes to the existing MODTRAN structure as discussed below.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 15, 1994
- Accession Number
- ADA298795
Entities
People
- H. Y. Yeh
- K. Stamnes