Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesosphere and rotational temperatures

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One of the standard methods to remotely sense the temperature of the mesopause region is based on spectroscopic measurements of the rotational temperatures of hydroxyl molecules. For the interpretation of the retrieved rotational temperatures, the aspect of rotational thermalization is of great importance. However, there is only a very limited number of studies on this topic. The aim of this project is to investigate rotationally-vibrationally excited OH molecules of the hydroxyl airglow layer in the upper mesosphere/lower thermosphere. For this purpose, a first-principle kinetic model of vibrationally-rotationally excited hydroxyl molecules will be developed. The model will be used to simulate concentrations of excited hydroxyl molecules and emission rates at different altitudes and for different atmospheric conditions. In particular, the rotational state distributions will be analyzed to assess deviations from local thermodynamic equilibrium. The model results will be compared to ground-based and satellite measurements.