ANALYSIS OF THE UPPER-ATMOSPHERE CO2(NU-2) VIBRATIONAL TEMPERATURES RETRIEVED FROM ATMOS SPACELAB 3 OBSERVATIONS

An analysis of the upper atmospheric (80-116 km) CO2(nu2) vibrational temperatures retrieved from atmospheric trace molecule spectroscopy (ATMOS) experiment Spacelab 3 spectra by using a nonlocal thermodynamic equilibrium (non-LTE) radiative transfer model is presented. Thermal collisions with atmospheric atomic oxygen keep this vibrational state very close to LTE up to around 100 km. Above this height the different deviations from LTE retrieved from ATMOS/Spacelab 3 spectra for the northern and southern hemispheres are explained in terms of this collisional process and in terms of the different kinetic temperature profiles measured at those locations. From these simultaneous observations of the kinetic and CO2(nu2) vibrational temperatures a deactivation rate of CO2(nu2) by (O(P))-P-3 has been derived which, considering the available climatologies of the concentration of this compound, leads to a rate coefficient value between 3 and 6 x 10(-12) cm3 s-1 and favors an independent or negative temperature dependence rate constant for the atmospheric temperature range. Cooling rates induced by the CO2 15-mum fundamental band in the upper mesosphere and lower thermosphere (80-116 km) were derived from the simultaneous kinetic temperature, CO2(mu2) vibrational temperature, and CO2 concentration, as measured by ATMOS/Spacelab 3, and found to be a factor of between 5 and 10 times larger than those generally accepted until very recently.