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| Titel |
Position error in profiles retrieved from MIPAS observations with a 1-D algorithm |
| VerfasserIn |
M. Carlotti, E. Arnone, E. Castelli, B. M. Dinelli, E. Papandrea |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-20), S.419-429 |
| Datensatznummer |
250017399
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| Publikation (Nr.) |
 copernicus.org/amt-6-419-2013.pdf |
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| Zusammenfassung |
| The information load (IL) analysis, first introduced for
the two-dimensional approach (Carlotti and Magnani,
2009), is applied to the inversion of
MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) observations operated with a 1-dimensional (1-D) retrieval algorithm. The IL
distribution of MIPAS spectra is shown to be often asymmetrical with respect
to the tangent points of the observations and permits us to define the
preferential latitude where the profiles retrieved with a 1-D algorithm
should be geo-located. Therefore, defining the geo-location of the retrieved
profile by means of the tangent points leads to a "position error". We assess the amplitude of the position error for some of
the MIPAS main products and we show that the IL analysis can also be used as
a tool for the selection of spectral intervals that, when analyzed, minimize the
position error of the retrieved profile. When the temperature (T) profiles
are used for the retrieval of volume mixing ratio (VMR) of atmospheric
constituents, the T-position error (of the order of 1.5 degrees of latitude)
induces a VMR error that is directly connected with the horizontal T
gradients. Temperature profiles can be externally-provided or determined in
a previous step of the retrieval process. In the first case, the IL analysis
shows that a meaningful fraction (often exceeding 50%) of the VMR error
deriving from the 1-D approximation is to be attributed to the mismatch
between the position assigned to the external T profile and the positions
where T is required by the analyzed observations. In the second case the
retrieved T values suffer by an error of 1.5–2 K due to neglecting the
horizontal variability of T; however the error induced on VMRs is of minor
concern because of the generally small mismatch between the IL distribution
of the observations analyzed to retrieve T and those analyzed to
retrieve the VMR target. An estimate of the contribution of the T-position error to
the error budget is provided for MIPAS main products. This study shows that
the information load analysis can be successfully exploited in a 1-D
context that makes the assumption of horizontal homogeneity of the analyzed
portion of atmosphere. The analysis that we propose can be extended to the
1-D inversion of other limb-sounding experiments. |
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