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| Titel |
Processing of GRAS/METOP radio occultation data recorded in closed-loop and raw-sampling modes |
| VerfasserIn |
M. E. Gorbunov, K. B. Lauritsen, H.-H. Benzon, G. B. Larsen, S. Syndergaard, M. B. Sørensen |
| 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 ; 4, no. 6 ; Nr. 4, no. 6 (2011-06-09), S.1021-1026 |
| Datensatznummer |
250002005
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| Publikation (Nr.) |
 copernicus.org/amt-4-1021-2011.pdf |
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| Zusammenfassung |
| Instrument GRAS (Global Navigation Satellite System Receiver for Atmospheric
Sounding) on-board of the Metop-A satellite was activated on 27 October
2006. Currently, Metop-A is a fully operational satellite with GRAS
providing from 650–700 occultations per day. We describe our processing of
GRAS data based on the modification of our OCC software, which was modified
to become capable of reading and processing GRAS data. We perform a
statistical comparison of bending angles and refractivities derived from
GRAS data with those derived from ECMWF analyses. We conclude that GRAS data
have error characteristics close to those of COSMIC data. In the height
range 10–30 km, the systematic refractivity difference GRAS–ECMWF is of
the order of 0.1–0.2 %, and the standard deviation is 0.3–0.6 %. In
the lower troposphere GRAS refractivity and bending angle indicate a
negative bias, which reaches its maximum value in the tropics. In particular
the retrieved refractivity is biased by up to 2.5 %. The negative bias
pattern is similar to that found in the statistical validation of COSMIC
data. This makes it probable that the bias should not be attributed to the
instrument design or hardware. |
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