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| Titel |
Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds |
| VerfasserIn |
D. J. Sandford, C. L. Beldon, R. E. Hibbins, N. J. Mitchell |
| 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 ; 10, no. 21 ; Nr. 10, no. 21 (2010-11-04), S.10273-10289 |
| Datensatznummer |
250008866
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| Publikation (Nr.) |
 copernicus.org/acp-10-10273-2010.pdf |
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| Zusammenfassung |
Zonal and meridional winds have been measured in the upper mesosphere and
lower thermosphere at polar latitudes using two ground-based meteor radars.
One radar is located at Rothera (68° S, 68° W) in the
Antarctic and has been operational since February 2005. The second radar is
located at Esrange (68° N, 21° E) in the Arctic and has
been operational since October 1999. Both radars have produced relatively
continuous measurements. Here we consider measurements made up to the end of
2009. Both radars are of similar design and at conjugate geographical
latitudes, making the results directly comparable and thus allowing
investigation of the differences in the mean winds of the Antarctic and
Arctic regions. The data from each radar have been used to construct
climatologies of monthly-mean zonal and meridional winds at heights between
80 and 100 km. Both Antarctic and Arctic data sets reveal seasonally varying
zonal and meridional winds in which the broad pattern repeats from year to
year. In particular, the zonal winds display a strong shear in summer
associated with the upper part of the westward summertime zonal jet. The
winds generally reverse to eastward flow at heights of ~90 km. The
zonal winds are eastward throughout the rest of the year. The meridional
winds are generally equatorward over both sites, although brief episodes of
poleward flow are often evident near the equinoxes and during winter. The
strongest equatorward flows occur at heights of ~90 km during summer.
There are significant differences between the mean winds observed in the
Antarctic and Arctic. In particular, the westward winds in summer are
stronger and occur earlier in the season in the Antarctic compared with the
Arctic. The eastward winds evident above the summertime zonal wind reversal
are significantly stronger in the Arctic. The summertime equatorward flow in
the Antarctic is slightly weaker, but occurs over a greater depth than is
the case in the Arctic.
Comparisons of these observations with those of the URAP and HWM-07 empirical
models reveal a number of significant differences. In particular, the zonal
winds observed in the Antarctic during wintertime are significantly weaker
than those of URAP. However, the URAP zonal winds are a good match to the
observations of the Arctic. Significant differences are evident between the
observations and HWM-07. In particular, the strong wintertime zonal winds of
the Arctic in HWM-07 are not evident in the observations and the summertime
zonal winds in HWM-07 are systematically stronger than observed. The
agreement with meridional winds is generally poor.
There is a significant amount of inter-annual variability in the observed
zonal and meridional winds. Particularly high variability is observed in the
Arctic zonal winds in spring and is probably associated with stratospheric
warmings. |
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