| 1. |
- Von Clarmann, T., et al.
(author)
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A blind test retrieval experiment for infrared limb emission spectrometry
- 2003
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In: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 108:D23
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Journal article (peer-reviewed)abstract
- The functionality and characteristics of six different data processors (i.e., retrieval codes in their actual software and hardware environment) for analysis of high-resolution limb emission infrared spectra recorded by the space-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) have been validated by means of a blind test retrieval experiment based on synthetic spectra. For this purpose a self-consistent set of atmospheric state parameters, including pressure, temperature, vibrational temperatures, and abundances of trace gases and aerosols, has been generated and used as input for radiative transfer calculations for MIPAS measurement geometry and configuration. These spectra were convolved with the MIPAS field of view, spectrally degraded by the MIPAS instrument line shape, and, finally, superimposed with synthetic measurement noise. These synthetic MIPAS measurements were distributed among the participants of the project “Advanced MIPAS level-2 data analysis” (AMIL2DA), who performed temperature and species abundance profile retrievals by inverse radiative transfer calculations. While the retrieved profiles of atmospheric state parameters reflect some characteristics of the individual data processors, it was shown that all the data processors under investigation are capable of producing reliable results in the sense that deviations of retrieved results from the reference profiles are within the margin that is consistent with analytical error estimation.
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| 2. |
- Funke, Bernd, et al.
(author)
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New non-LTE retrieval method for atmospheric parameters from MIPAS/ENVISAT emission spectra at 5.3 μm
- 2002
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In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 4539, s. 396-405
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Journal article (peer-reviewed)abstract
- Atmospheric emissions at 5.3 μm will be measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a high-resolution limb sounder on board the European polar platform ENVISAT, scheduled to be launched in 2001. Measured spectra at 5.3 μm contain information on important atmospheric quantities such as NO volume mixing ratio, thermospheric temperature, and chemical NO production rates. However, the scientific analysis of this spectral region has to deal with complex non-local thermodynamic equilibrium (non-LTE) effects. A conventional non-LTE retrieval approach using ab initio vibrational temperatures cannot be applied due to rotational and spin-orbit non-LTE of NO in the thermosphere, and the dependence of NO state populations on the NO abundance itself caused by chemical excitations. An innovative non-LTE retrieval method enabling the treatment of vibrational, rotational, and spin non-LTE as well as a dependence of the non-LTE state distribution on the retrieval target quantities has thus been developed for the MIPAS data analysis. The ability of the developed non-LTE inversion tool to retrieve NO abundance profiles, thermospheric temperature profiles, and NO mean production rates by NO2 photolysis in the stratosphere and N+O2 combination in the thermosphere is demonstrated by means of a feasibility study.
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| 3. |
- López-Puertas, M., et al.
(author)
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Non-LTE studies for the analysis of MIPAS/ENVISAT data
- 2002
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 4539, s. 381-395
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Journal article (peer-reviewed)abstract
- The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb sounder on board the European polar platform ENVISAT, scheduled for launch late in 2001. Three main characteristics converge in MIPAS which make it a very useful instrument for non-LTE studies: its wide spectral coverage (4.15-14.6 μm or 680-2275 cm-1); high spectral resolution (0.03 cm-1), and high sensitivity; all of this in addition to its global spatial coverage. In this paper we present an overview of the non-LTE studies that have been carried out in preparation for the analysis of MIPAS data, including the evaluation of non-LTE effects in the operational processing, focussed in the stratosphere, and the retrieval of species that normally emit under non-LTE conditions. The current mission plan for measuring the non-LTE upper atmosphere is described, as well as the general purpose non-LTE retrieval scheme developed for analyzing those measurements.
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