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| Titel |
Where to see climate change best in radio occultation variables – study using GCMs and ECMWF reanalyses |
| VerfasserIn |
B. C. Lackner, A. K. Steiner, G. Kirchengast |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 11 ; Nr. 29, no. 11 (2011-11-29), S.2147-2167 |
| Datensatznummer |
250017133
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| Publikation (Nr.) |
 copernicus.org/angeo-29-2147-2011.pdf |
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| Zusammenfassung |
| Radio occultation (RO) is a new technique to observe the upper troposphere and
lower stratosphere (UTLS), a region that reacts particularly sensitive to climate
change. Featuring characteristics such as long-term stability, SI traceability, all-weather
capability, global coverage, and high accuracy and vertical resolution, RO data fulfill the
requirements for climate monitoring in the UTLS. However, while a range of studies has shown the
climate utility of RO it has not yet been explored sytematically where to see climate change best
in RO variables. Therefore we perform here a systematic trend study for the RO variables
refractivity, pressure, and temperature (bending angle, not depending on height but impact
parameter, is left for separate study). The trends, given at geopotential height levels and for
layer gradients, are explored to determine seasons, geographic regions, and height domains, which
show a significant trend signal. Because continuous RO data are available since 2001 only,
reanalyses (ERA-40 and ERA-Interim) and global circulation model simulations of the
Intergovernmental Panel on Climate Change Assessment Report 4 (CCSM3, ECHAM5, HadCM3) are used as
proxy data for RO. It is shown that RO data are sensitive at different height ranges and that thus
several indicators of climate change can be retrieved. Refractivity emerges as indicator in the
lower stratosphere (LS) and tropopause region at about 14 km to 24 km, pressure over the whole
UTLS, and both in all large-scale regions except the polar caps. Temperature qualifies as
indicator in the upper troposphere below about 16 km and in the LS above about 21 km. Overall,
refractivity and pressure alone are adequate indicators for the UTLS, but temperature as commonly
used variable facilitates easy interpretation of results. Layer gradients were found to be further
sensitive indicators providing additional information. Besides large-scale global and hemispheric
means the tropics and the mid-latitudes appear as regions suitable to track climate change with RO
data. The results also point to the value of utilizing in addition to annual means specific
seasons, such as northern hemispheric fall and summer, for early climate signal detection. Since
RO data feature much better vertical resolution than the proxy data of this study, more detailed
insights can be expected when a longer RO record will be available. |
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