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Proceedings Paper

Empirical water vapor continuum models for infrared propagation
Author(s): Michael E. Thomas
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Paper Abstract

The characterization of the water vapor continuum remains an important problem concerning infrared propagation in the atmosphere. Radiometric imaging within the atmosphere in the 8 to 12 micrometers and 3 - 5 micrometers regions, and eye safe lidar in the 2 micrometers and 1.6 micrometers window regions require accurate knowledge of the water vapor continuum. Although the physical nature of the continuum is a complex problem, the observed frequency, pressure and temperature dependence can be represented reasonably well by simple mathematical functions consistent with far wing theories. This approach is the basis for current models used in LOWTRAN/MODTRAN and for the models listed in the SPIE/ERIM EO/IR Systems Handbook (Volume 2 Chapter 1). However, these models are based solely on a limited, but high quality, data set collected by a spectrometer and White cell. Additional information on oxygen broadening and temperature dependence is available from numerous laser measurements of the water vapor continuum. A survey of relevant experimental data is made to determine the best available measurements of the water vapor continuum in various atmospheric window regions. Then the data are fit to an empirical model over the entire window region. A good fit is obtained for typical atmospheric conditions covering the 8 to 12 micrometers and 3 to 5 micrometers regions. No experimental data, covering atmospheric conditions, exist in the 2 micrometers and 1.6 micrometers regions. However, models can be proposed based on far wing extrapolations of the bordering vibrational water vapor bands.

Paper Details

Date Published: 15 June 1995
PDF: 11 pages
Proc. SPIE 2471, Atmospheric Propagation and Remote Sensing IV, (15 June 1995); doi: 10.1117/12.211960
Show Author Affiliations
Michael E. Thomas, Johns Hopkins Univ. (United States)


Published in SPIE Proceedings Vol. 2471:
Atmospheric Propagation and Remote Sensing IV
J. Christopher Dainty, Editor(s)

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