Kinetic temperatures in the upper mesosphere and lower thermosphere derived from CRISTA limb radiance data
The CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA-1 and -2) experiments took place in November 1994 and August 1997, respectively. CRISTA measured the infrared limb radiance emitted by trace gases in several spectral channels from 4 to 71 μm. The high radiometric sensitivity and low level of instrumental noise achieved by liquid helium cooling allowed the derivation of atomic oxygen, carbon dioxide and ozone number densities in the upper mesosphere and lower thermosphere. In this altitude region the retrieval of kinetic temperature is complicated by the breakdown of local thermodynamic equilibrium (LTE) conditions. Using the non-LTE model that couples the collisional, radiative and photochemical processes the kinetic temperature was retrieved from the 15 μm CO2 emission by a forward run and global fit feedback method. The derived temperatures are compared with model predictions and climatologies based on rocket and satellite measurements. In the vicinity of the high latitude summer mesopause which provides the most difficult case for the non-LTE retrieval procedure, a very good agreement with temperature data from rocket soundings is found.
European Rocket and Balloon Programmes and Related Research
- Pub Date:
- August 2001