Non-LTE effects on retrieval of temperature from the CO2 laser bands using CIRRIS 1A data

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 IA) 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.