Atmospheric Absorption Applied to Plume Emission. Experimental and Analytical Investigations of Hot Gas Emission Attenuated by Cold Gases

Abstract
An experimental and theoretical study has been made of the atmospheric attenuation of plume radiation. A particular facet of this problem was examined, namely the effect of the correlation of the water vapor and CO2 emission lines of the plume with the corresponding absorption lines in the atmosphere. These correlations can produce lower effective transmittance of the plume radiation than the usual treatments of atmospheric attenuation predict. To measure the magnitude of correlation effects, experimental measurements were made of the radiance of a hot cell, filled with mixtures of CO2, H2O, N2 and other plume gases. These radiances were measured both unattenuated and attenuated by a long cool atmospheric path. A band model method to handle the line correlation effects was also developed. The authors were able to conclude that these correlation effects are severe enough in the 2.7 micrometers water vapor-CO2 band that their neglect can lead to an error of about 50% to a factor of two in computed radiances and radiant intensities for horizontal paths at 15 km altitude. It was also shown that the set of emission-absorption parameters compiled by Ludwig and the most commonly used to compute CO2 contributions to plume radiances, do not predict the measured emission-absorption spectra very well, while the water predictions showed adequate agreement. The measured emission-absorption spectra were also compared to the extensive line tabulation of McClatchey.

This publication has 0 references indexed in Scilit: