Interpretation of satellite measurements of the outgoing nonequilibrium IR radiation in the CO2 15-μm band:: 1.: Description of the method and analysis of its accuracy

The paper describes a method for retrieving the kinetic temperature, pressure, and concentrations of atmospheric gases as well as the nonequilibrium population of vibrational states of their molecules (vibrational temperatures) from the data of measuring the outgoing infrared limb radiation under non-local thermodynamic dynamic equilibrium conditions. A characteristic feature of the method lies in the fact that there is no need to model the processes controlling the nonequilibrium population of vibrational states. On the basis of numerical experiments and error-matrix calculations, we investigated the applicability of the method to the interpretation of the spectra recorded in the 15-mum band by the CRISTA satellite instrument. The inverse problem is formulated for the "effective" vibrational temperatures whose values are close to the vibrational temperatures of the first excited states of four most abundant isotopic variants of CO2 molecules. The numerical experiments conducted and the results of estimating, the method's accuracy from matrix-error calculations have shown that the use of this method for processing the CRISTA spectra allows the retrieval of the vertical profiles of kinetic temperature and vibrational temperature of the CO2 (626) isotope up to a height of 120 km with errors smaller than 9 and 3 K, respectively. The vibrational temperatures of three less abundant isotopes are retrieved with an error less than 8 K up to heights of 95-110 km. The method also enables the CO2 mixing ratio in the mesosphere to be estimated with an error of about 10%.