Modelling of the non-LTE populations of the nitric acid and methane vibrational states in the middle atmosphere

Javier Martin-Torres, Miguel A. López-Valverde, Manuel López-Puertas

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)1631-1647
Number of pages17
JournalJournal of Atmospheric and Solar-Terrestrial Physics
Volume60
Issue number17
DOIs
Publication statusPublished - Nov 15 1998
Externally publishedYes

Fingerprint

middle atmosphere
nitric acid
vibrational states
methane
modeling
remote sensing
mesosphere
solar radiation
local thermodynamic equilibrium
excitation
atmosphere
illumination
air
harmonics
gas
atmospheres
augmentation
radiation
temperature
gases

ASJC Scopus subject areas

  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science

Cite this

Modelling of the non-LTE populations of the nitric acid and methane vibrational states in the middle atmosphere. / Martin-Torres, Javier; López-Valverde, Miguel A.; López-Puertas, Manuel.

In: Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 60, No. 17, 15.11.1998, p. 1631-1647.

Research output: Contribution to journalArticle

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