Non-LTE Effects on Retrieval of Temperature from the CO2 Laser Bands Using CIRRIS-1A Data

Author: S. M. Miller and Hilary E. "Ned" Snell
Date: 
January 1, 2000
Type: 
Journal Article
Venue: 
Journal of Geophysical Research
Citation: 

Miller, S. M., J. Winick, and H. E. Snell (2000), Non-LTE effects on retrieval of temperature from the CO2 laser bands using CIRRIS 1A data, J. Geophys. Res., 105(D8), 10,193–10,202, doi:10.1029/1999JD901111.

It is well known that in the upper stratosphere and lower mesosphere, the CO2 laser band (00011 – 10001) transitions are populated by both local thermodynamic equilibrium (LTE) and non-LTE mechanisms. Examination of infrared (IR) limb emission measurements from the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS 1A) experiment clearly illustrates this effect. The presence of non-LTE emissions, if left unaccounted for, will severely degrade the retrieval of kinetic temperature profiles. We have applied a non-LTE compensation technique whereby the non-LTE component is modeled and the resulting non-LTE radiance is subtracted from the measured radiances. The kinetic temperature profile is then retrieved utilizing the modified data. As a means of validating this approach, we have compared the resulting temperature profiles to ones retrieved using the 792 cm−1 Q branch of CO2, the (11101 – 10002) transition, which is not significantly affected by non-LTE excitation.