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| Titel |
Retrieval of temperature and water vapor profiles from radio occultation refractivity and bending angle measurements using an Optimal Estimation approach: a simulation study |
| VerfasserIn |
A. Engeln, G. Nedoluha |
| 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 ; 5, no. 6 ; Nr. 5, no. 6 (2005-07-07), S.1665-1677 |
| Datensatznummer |
250002913
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| Publikation (Nr.) |
 copernicus.org/acp-5-1665-2005.pdf |
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| Zusammenfassung |
| The Optimal Estimation Method is used to retrieve temperature and water
vapor profiles from simulated radio occultation measurements in order to
assess how different retrieval schemes may affect the assimilation of this
data. High resolution ECMWF global fields are used by a state-of-the-art
radio occultation simulator to provide quasi-realistic bending angle and
refractivity profiles. Both types of profiles are used in the
retrieval process to assess their advantages and disadvantages. The
impact of the GPS measurement is expressed as an improvement over
the a priori knowledge (taken from a 24h old analysis). Large
improvements are found for temperature in the upper troposphere and
lower stratosphere. Only very small improvements are found in the
lower troposphere, where water vapor is present. Water vapor
improvements are only significant between about 1 km to 7 km. No
pronounced difference is found between retrievals based upon bending
angles or refractivity. Results are compared to idealized
retrievals, where the atmosphere is spherically symmetric and
instrument noise is not included. Comparing idealized to
quasi-realistic calculations shows that the main impact of a ray
tracing algorithm can be expected for low latitude water vapor,
where the horizontal variability is high. We also address the effect
of altitude correlations in the temperature and water vapor.
Overall, we find that water vapor and temperature retrievals using
bending angle profiles are more CPU intensive than
refractivity profiles, but that they do not provide significantly
better results. |
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