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| Titel |
Dynamic statistical optimization of GNSS radio occultation bending angles: advanced algorithm and performance analysis |
| VerfasserIn |
Y. Li, G. Kirchengast, B. Scherllin-Pirscher, R. Norman, Y. B. Yuan, J. Fritzer, M. Schwaerz, K. Zhang |
| 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 ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-25), S.3447-3465 |
| Datensatznummer |
250116542
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| Publikation (Nr.) |
 copernicus.org/amt-8-3447-2015.pdf |
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| Zusammenfassung |
| We introduce a new dynamic statistical optimization algorithm to initialize
ionosphere-corrected bending angles of Global Navigation Satellite System
(GNSS)-based radio occultation (RO) measurements. The new algorithm
estimates background and observation error covariance matrices with
geographically varying uncertainty profiles and realistic global-mean
correlation matrices. The error covariance matrices estimated by the new
approach are more accurate and realistic than in simplified existing
approaches and can therefore be used in statistical optimization to provide
optimal bending angle profiles for high-altitude initialization of the
subsequent Abel transform retrieval of refractivity. The new algorithm is
evaluated against the existing Wegener Center Occultation Processing System
version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from
January and July 2008 and real observed CHAllenging Minisatellite Payload
(CHAMP) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements from
the complete months of January and July 2008. The following is achieved for
the new method's performance compared to OPSv5.6: (1) significant reduction
of random errors (standard deviations) of optimized bending angles down to
about half of their size or more; (2) reduction of the systematic
differences in optimized bending angles for simulated MetOp data; (3)
improved retrieval of refractivity and temperature profiles; and (4)
realistically estimated global-mean correlation matrices and realistic
uncertainty fields for the background and observations. Overall the results
indicate high suitability for employing the new dynamic approach in the
processing of long-term RO data into a reference climate record, leading to
well-characterized and high-quality atmospheric profiles over the entire
stratosphere. |
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