TY - JOUR
T1 - Modelling of the non-LTE populations of the nitric acid and methane vibrational states in the middle atmosphere
AU - Martín-Torres, F. Javier
AU - López-Valverde, Miguel A.
AU - López-Puertas, Manuel
N1 - Funding Information:
We wish to thank the Satellite Data Utilization Office (Code 910.4) and the DistributedActiveArchive Center (Code 902.2) at Goddard Space Flight Center, Greenbelt, MD 2077, U.S.A.for theproduction and distribution of the TOVS data, an activity that was sponsored by NASAsMission toPlanet Earth program. We have been supported by CICYT under contractsESP94-0803,ESP96-0623. This work was also partially supported by the European Space Agency.We wish alsoto thank G.M. Shved for his valuable suggestions.
PY - 1998/11/15
Y1 - 1998/11/15
N2 - A modelling of the non-LTE populations of the HNO3 and CH4 vibrational levels in the middle atmosphere has been carried out and the results are presented. The work is oriented to assess the potential impact of non-LTE effects on the remote sensing of these gases. The models developed for this purpose include a complete set of radiative and collisional processes. In order to cover typical and extreme remote sensing scenarios, the models have been applied to different atmospheric and solar illumination conditions. The vibrational levels responsible for the major emissions of HNO3 are found to be in LTE up to the lower mesosphere, driven by the dominant V-T processes with the air molecules. In the non-LTE region, the absorption from the warmer tropospheric layers and solar direct excitation produce small enhancements over the equilibrium populations. The mesospheric CH4 vibrational temperatures are mainly determined by two mechanisms: the radiative absorption of the upcoming radiation emitted by the lower layers of the atmosphere, and the near-resonant vibrational coupling between the CH4 levels and the first vibrationally excited level of O2. By day, non-LTE is significantly enhanced as a consequence of the collisional relaxation of overtone and combinational states excited by the solar radiation at 3.3 μm. The effects derived from the uncertainties in the parameters of the models have been studied.
AB - A modelling of the non-LTE populations of the HNO3 and CH4 vibrational levels in the middle atmosphere has been carried out and the results are presented. The work is oriented to assess the potential impact of non-LTE effects on the remote sensing of these gases. The models developed for this purpose include a complete set of radiative and collisional processes. In order to cover typical and extreme remote sensing scenarios, the models have been applied to different atmospheric and solar illumination conditions. The vibrational levels responsible for the major emissions of HNO3 are found to be in LTE up to the lower mesosphere, driven by the dominant V-T processes with the air molecules. In the non-LTE region, the absorption from the warmer tropospheric layers and solar direct excitation produce small enhancements over the equilibrium populations. The mesospheric CH4 vibrational temperatures are mainly determined by two mechanisms: the radiative absorption of the upcoming radiation emitted by the lower layers of the atmosphere, and the near-resonant vibrational coupling between the CH4 levels and the first vibrationally excited level of O2. By day, non-LTE is significantly enhanced as a consequence of the collisional relaxation of overtone and combinational states excited by the solar radiation at 3.3 μm. The effects derived from the uncertainties in the parameters of the models have been studied.
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U2 - 10.1016/S1364-6826(98)00108-4
DO - 10.1016/S1364-6826(98)00108-4
M3 - Article
AN - SCOPUS:0344417004
VL - 60
SP - 1631
EP - 1647
JO - Journal of Atmospheric and Solar-Terrestrial Physics
JF - Journal of Atmospheric and Solar-Terrestrial Physics
SN - 1364-6826
IS - 17
ER -