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Proceedings Paper

Improved atmospheric radiance calculations using CO2 P/R-branch line mixing
Author(s): S. De Souza-Machado; L. Larrabee Strow; David C. Tobin; Scott E. Hannon
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Paper Abstract

New high-spectral resolution satellite sounders will use channels located between CO2 lines for temperature retrievals. Transmittances for these channels are dominated by spectral line wings that are strongly influenced by line-mixing and duration-of-collision effects. Previous studies demonstrated the importance of Q-branch line mixing for atmospheric sounding in the 15 micrometer region. This work presents an improved model of P/R-branch line mixing and duration-of- collision effects on CO2 transmittances in the 4.3 micrometer and 15 micrometer regions, based on laboratory and spectroscopy data. Most line-by-line codes model non- Lorentzian behavior by using the Cousin chi-function. This empirical function incorporates both P/R line-mixing and duration-of-collision effects by using many parameters. It is common to use the Cousin model parameters obtained from the 4 micrometer band in the 15 micrometer region, overestimating the amount of line-mixing. Comparisons to radiance data taken with high resolution interferometers that fly on NASA's ER-2 partially validates our model. The biggest improvements are at 4.3 micrometer where the differences are reduced by more than 2K, compared to using the Cousin model.

Paper Details

Date Published: 8 December 1999
PDF: 8 pages
Proc. SPIE 3867, Satellite Remote Sensing of Clouds and the Atmosphere IV, (8 December 1999); doi: 10.1117/12.373071
Show Author Affiliations
S. De Souza-Machado, Univ. of Maryland/Baltimore County (United States)
L. Larrabee Strow, Univ. of Maryland/Baltimore County (United States)
David C. Tobin, Univ. of Wisconsin/Madison (United States)
Scott E. Hannon, Univ. of Maryland/Baltimore County (United States)

Published in SPIE Proceedings Vol. 3867:
Satellite Remote Sensing of Clouds and the Atmosphere IV
Jaqueline E. Russell, Editor(s)

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