| 1. |
- López-Puertas, M., et al.
(författare)
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Non-local thermodynamic equilibrium limb radiances for the mipas instrument on Envisat-1
- 1998
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 59:3-5, s. 377-403
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation of the effects that the assumption of local thermodynamic equilibrium (LTE) has on the retrieval of pressure, temperature and the five primary target gases (O3, H2O, CH4, N2O, and HNO3) from spectra to be taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the Envisat-1 platform has been conducted. For doing so, non-LTE and LTE limb radiances in the spectral range of 680–2275 cm−1 (4.15–14.6 μm) with a resolution of 0.05 cm−1 at tangent heights from 10 to 70 km have been computed. These calculations included the most updated non-LTE populations of a large number of vibrational levels of the CO2, O3, H2O, CH4, N2O and HNO3 molecules which cause the most prominent atmospheric infrared emissions. A discussion of the most important non-LTE effects on the limb radiances as well as on the retrievals of pressure-temperature and volume mixing ratios of O3, H2O, CH4, N2O, and HNO3 is presented, together with the most important non-LTE issues that could be studied with the future coming of MIPAS data.
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| 2. |
- Manuilova, R.O., et al.
(författare)
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Modelling of non-LTE limb spectra of i.r. ozone bands for the MIPAS space experiment
- 1998
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 59:3-5, s. 405-422
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Tidskriftsartikel (refereegranskat)abstract
- A new model for calculating the populations of the ozone vibrational states under non-LTE (Local Thermodynamic Equilibrium) conditions is presented. In the model, 23 vibrational levels of the O3 molecule, as well as three vibrational levels of the O2 molecule and two vibrational levels of the N2 molecule, are considered. The radiative transfer at the break-down of LTE was treated explicitly for 150 000 ro-vibrational transitions. The populations obtained were used to calculate limb radiances in various spectral regions of the 4.8 and 9.6 μm bands. Test retrievals of O3 vertical volume mixing ratio (VMR) profiles with a radiance model disregarding non-LTE were performed in order to assess the potential impact of non-LTE effects on the retrieval of the O3 abundances from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) measurements.
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| 3. |
- Martin-Torres, Javier, et al.
(författare)
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Modelling of the non-LTE populations of the nitric acid and methane vibrational states in the middle atmosphere
- 1998
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - 1364-6826 .- 1879-1824. ; 60:17, s. 1631-
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Tidskriftsartikel (refereegranskat)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.
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