EGU2020-15350
https://doi.org/10.5194/egusphere-egu2020-15350
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesopause region

Justus Notholt1, Holger Winkler1, and Stefan Noll2
Justus Notholt et al.
  • 1University of Bremen, Institute of Environmental Physics (IUP), Physics, Bremen, Germany (notholt@uni-bremen.de)
  • 2Institut für Physik, Universität Augsburg, Augsburg, Germany

One of the standard methods to remotely sense the temperature of the mesopause region is based on spectroscopic measurements of near-infrared emissions of vibrationally-rotationally excited hydroxyl molecules, and to calculate  rotational temperatures. For the interpretation of the retrieved temperatures, the aspect of rotational thermalization is of great importance. We present results of a first-principle kinetic model of vibrationally-rotationally excited hydroxyl molecules which accounts for chemical production and loss processes as well as radiative and collision-induced vibrational-rotational transitions. The model allows one to assess deviations of the rotational populations from local thermodynamic equilibrium, and to identify the key parameters which control the rotational thermalization processes. The model simulations reproduce the observed bimodality in temperatures, i.e. a cold temperature component dominating the population of low rotational states, and a hot temperature component dominating higher states. The model results are compared to measurement data from the UVES echelle spectrograph at Cerro Paranal in Chile (Presentation EGU2020-3169) which allows us to confine free model parameters such as the rotational state changes in vibrational quenching process.

How to cite: Notholt, J., Winkler, H., and Noll, S.: Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesopause region , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15350, https://doi.org/10.5194/egusphere-egu2020-15350, 2020

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