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| Titel |
On the comparisons of tropical relative humidity in the lower and middle troposphere among COSMIC radio occultations and MERRA and ECMWF data sets |
| VerfasserIn |
P. Vergados, A. J. Mannucci, C. O. Ao, J. H. Jiang, H. Su |
| 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. 4 ; Nr. 8, no. 4 (2015-04-17), S.1789-1797 |
| Datensatznummer |
250116300
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| Publikation (Nr.) |
 copernicus.org/amt-8-1789-2015.pdf |
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| Zusammenfassung |
| The spatial variability of the tropical tropospheric
relative humidity (RH) throughout the vertical extent of the troposphere is
examined using Global Positioning System Radio Occultation (GPSRO)
observations from the Constellation Observing System for Meteorology,
Ionosphere, and Climate (COSMIC) mission. These high vertical resolution
observations capture the detailed structure and moisture budget of the
Hadley Cell circulation. We compare the COSMIC observations with the
European Center for Medium-range Weather Forecast (ECMWF) Reanalysis
Interim (ERA-Interim) and the Modern-Era Retrospective analysis for Research
and Applications (MERRA) climatologies. Qualitatively, the spatial pattern
of RH in all data sets matches up remarkably well, capturing distinct
features of the general circulation. However, RH discrepancies exist between
ERA-Interim and COSMIC data sets that are noticeable across the tropical
boundary layer. Specifically, ERA-Interim shows a drier Intertropical
Convergence Zone (ITCZ) by 15–20% compared to both COSMIC and MERRA data
sets, but this difference decreases with altitude. Unlike ECMWF, MERRA shows
an excellent agreement with the COSMIC observations except above 400 hPa,
where GPSRO observations capture drier air by 5–10%. RH climatologies
were also used to evaluate intraseasonal variability. The results indicate
that the tropical middle troposphere at ±5–25° is most
sensitive to seasonal variations. COSMIC and MERRA data sets capture the
same magnitude of the seasonal variability, but ERA-Interim shows a weaker
seasonal fluctuation up to 10% in the middle troposphere inside the dry
air subsidence regions of the Hadley Cell. Over the ITCZ, RH varies by
maximum 9% between winter and summer. |
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