Rapid computation of spectrally integrated non-LTE limb emission

Martin G. Mlynczak; Daphne S. Olander; Manuel Lopez-Puertas; James M. Russell III; Larry L. Gordley

doi:10.1117/12.187581

30 September 1994 Rapid computation of spectrally integrated non-LTE limb emission

Martin G. Mlynczak, Daphne S. Olander, Manuel Lopez-Puertas, James M. Russell III, Larry L. Gordley

Proceedings Volume 2266, Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research; (1994) https://doi.org/10.1117/12.187581
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

The interpretation of infrared radiance measurements made by satellite-borne limb scanning broadband radiometers requires accurate and computationally fast techniques with which to evaluate the equation of radiative transfer. This requirement is made even more stringent when analyzing measurements of non-LTE emission from the terrestrial mesosphere and lower thermosphere. In principle, line-by-line calculations which explicitly account for the departure from thermodynamic equilibrium in both the source functions and the transmittances are necessary. In this paper we extend the emissivity growth approximation (EGA) technique developed for LTE conditions to the non-LTE environment. Computations of the non-LTE spectrally integrated limb radiance for the molecular oxygen airglow (1.27 micrometers and 762 nm), ozone and carbon dioxide in the 9 - 11 micrometers spectral interval, carbon monoxide (4.6 micrometers ), nitric oxide (5.3 micrometers ), and carbon dioxide (15 micrometers ) are presented. Using the non-LTE form of the EGA, the spectrally integrated limb emission is calculated for 35 tangent heights in the mesosphere and lower thermosphere (requiring a total of 1200 atmospheric layers) with line-by-line accuracy in only approximately 0.25 sec of CPU time on readily available desktop computer hardware, while the corresponding line-by-line calculations may require tens of minutes. The non-LTE EGA technique allows minor constituent retrieval algorithms to readily include non-LTE effects limited only by the a priori knowledge of the departure from LTE in the observed bands.

Citation Download Citation

Martin G. Mlynczak, Daphne S. Olander, Manuel Lopez-Puertas, James M. Russell III, and Larry L. Gordley "Rapid computation of spectrally integrated non-LTE limb emission", Proc. SPIE 2266, Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research, (30 September 1994); https://doi.org/10.1117/12.187581

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