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Proceedings Paper

MODTRAN2: evolution and applications
Author(s): Gail P. Anderson; James H. Chetwynd Jr.; F. X. Kneizys; L. M. Kimball; Lawrence S. Bernstein; Prabhat K. Acharya; Alexander Berk; David C. Robertson; Leonard W. Abreu; Eric P. Shettle
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Paper Abstract

MODTRAN2' is the most recent version of MODTRAJP, the Moderate Resolution Atmospheric Radiance and Transmittance Model, officially released by the Geophysics Directorate, Phillips Laboratory, in early 1993. It encompasses all the capabilities of LOWTRAN 73, the historic 20 cni' resolution (full width at half maximum, FWHM) radiance code, but incorporates a much more sensitive molecular band model with 2 ciii' resolution. The band model is based directly upon the HITRAN4 spectral parameters, including both temperature and pressure (line shape) dependencies. Because the band model parameters and their applications to transmittance calculations have been independently developed using equivalent width "binning" procedures, validation against full Voigtline-by-line calculations (eg. FASCODEb) is important. Extensive spectral comparisons have shown excellent agreement. In addition, simple timing runs of MODTRAN vs. FASCOD3P (released in 1992) show an improvement of more than a factor of 100 for a typical 500 cm spectral interval and comparable vertical layering. It has been previously established that not only is MODTRAN an excellent band model for "full path" calculations (that is, radiance and/or transmittance from point A to point B), but it replicates layer-specific quantities to a very high degree of accuracy6. Such layer quantities, derived from ratios and differences of longer path MODTRAN calculations from point A to adjacent layer boundaries, can be used to provide inversion algorithm weighting functions or similarly formulated quantities. One of the most exciting new applications is the rapid calculation of reliable IR cooling rates7, including species, altitude, and spectral distinctions, as well as the standard integrated quantities. Comparisons with prior line-by-line cooling rate calculations'9 are excellent, and the techniques can be extended to incorporate global climatoIogies°.

Paper Details

Date Published: 29 June 1994
PDF: 10 pages
Proc. SPIE 2222, Atmospheric Propagation and Remote Sensing III, (29 June 1994); doi: 10.1117/12.177956
Show Author Affiliations
Gail P. Anderson, Air Force Phillips Lab. (United States)
James H. Chetwynd Jr., Air Force Phillips Lab. (United States)
F. X. Kneizys, Air Force Phillips Lab. (United States)
L. M. Kimball, Air Force Phillips Lab. (United States)
Lawrence S. Bernstein, Spectral Sciences, Inc. (United States)
Prabhat K. Acharya, Spectral Sciences, Inc. (United States)
Alexander Berk, Spectral Sciences, Inc. (United States)
David C. Robertson, Spectral Sciences, Inc. (United States)
Leonard W. Abreu, ONTAR Corp. (United States)
Eric P. Shettle, Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 2222:
Atmospheric Propagation and Remote Sensing III
Walter A. Flood; Walter B. Miller, Editor(s)

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