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| Titel |
MIPAS level 2 operational analysis |
| VerfasserIn |
P. Raspollini, C. Belotti, A. Burgess, B. Carli, M. Carlotti, S. Ceccherini, B. M. Dinelli, A. Dudhia, J.-M. Flaud, B. Funke, M. Höpfner, M. López-Puertas, V. Payne, C. Piccolo, J. J. Remedios, M. Ridolfi, R. Spang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 12 ; Nr. 6, no. 12 (2006-12-18), S.5605-5630 |
| Datensatznummer |
250004207
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| Publikation (Nr.) |
 copernicus.org/acp-6-5605-2006.pdf |
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| Zusammenfassung |
The MIPAS (Michelson Interferometer for Passive Atmospheric Sounding)
instrument has been operating on-board the ENVISAT satellite since March
2002. In the first two years, it acquired in a nearly continuous manner high
resolution (0.025 cm−1 unapodized) emission spectra of the Earth's
atmosphere at limb in the middle infrared region. This paper describes the
level 2 near real-time (NRT) and off-line (OL) ESA processors that have been
used to derive level 2 geophysical products from the calibrated and
geolocated level 1b spectra. The design of the code and the analysis
methodology have been driven by the requirements for NRT processing. This
paper reviews the performance of the optimized retrieval strategy that has
been implemented to achieve these requirements and provides estimated error
budgets for the target products: pressure, temperature, O3, H2O,
CH4, HNO3, N2O and NO2, in the altitude measurement
range from 6 to 68 km.
From application to real MIPAS data, it was found that no change was needed
in the developed code although an external algorithm was introduced to
identify clouds with high opacity and to exclude affected spectra from the
analysis. In addition, a number of updates were made to the set-up
parameters and to auxiliary data. In particular, a new version of the MIPAS
dedicated spectroscopic database was used and, in the OL analysis, the
retrieval range was extended to reduce errors due to uncertainties in
extrapolation of the profile outside the retrieval range and more stringent
convergence criteria were implemented.
A statistical analysis on the χ2 values obtained in one year of
measurements shows good agreement with the a priori estimate of the forward
model errors. On the basis of the first two years of MIPAS measurements the
estimates of the forward model and instrument errors are in general found to
be conservative with excellent performance demonstrated for frequency
calibration. It is noted that the total retrieval error is limited by
forward model errors which make effectless a further reduction of random
errors. However, such a reduction is within the capabilities of MIPAS
measurements, which contain many more spectral signatures of the target
species than what has currently been used. Further work is needed to reduce the
amplitude of the forward model errors, so that the random error and the
total error budget can be reduced accordingly.
The importance of the Averaging kernels for a full characterization of the
target products is underlined and the equations are provided for their
practical applications. |
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