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| Titel |
Mean winds, temperatures and the 16- and 5-day planetary waves in the mesosphere and lower thermosphere over Bear Lake Observatory (42° N, 111° W) |
| VerfasserIn |
K. A. Day, M. J. Taylor, 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 ; 12, no. 3 ; Nr. 12, no. 3 (2012-02-10), S.1571-1585 |
| Datensatznummer |
250010647
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| Publikation (Nr.) |
 copernicus.org/acp-12-1571-2012.pdf |
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| Zusammenfassung |
Atmospheric temperatures and winds in the mesosphere and lower thermosphere
have been measured simultaneously using the Aura satellite and a meteor radar
at Bear Lake Observatory (42° N, 111° W), respectively. The
data presented in this study is from the interval March 2008 to July 2011.
The mean winds observed in the summer-time over Bear Lake Observatory show
the meridional winds to be equatorward at meteor heights during April−August
and to reach monthly-mean velocities of −12 m s−1. The mean winds
are closely related to temperatures in this region of the atmosphere and in
the summer the coldest mesospheric temperatures occur about the same time as
the strongest equatorward meridional winds. The zonal winds are eastward
through most of the year and in the summer strong eastward zonal wind shears
of up to ~4.5 m s−1 km−1 are present. However, westward
winds are observed at the upper heights in winter and sometimes during the
equinoxes. Considerable inter-annual variability is observed in the mean
winds and temperatures.
Comparisons of the observed winds with URAP and HWM-07 reveal some large
differences. Our radar zonal wind observations are generally more eastward
than predicted by the URAP model zonal winds. Considering the radar
meridional winds, in comparison to HWM-07 our observations reveal equatorward
flow at all meteor heights in the summer whereas HWM-07 suggests that only
weakly equatorward, or even poleward flows occur at the lower heights.
However, the zonal winds observed by the radar and modelled by HWM-07 are
generally similar in structure and strength.
Signatures of the 16- and 5-day planetary waves are clearly evident in both
the radar-wind data and Aura-temperature data. Short-lived wave events can
reach large amplitudes of up to ~15 m s−1 and 8 K and
20 m s−1 and 10 K for the 16- and 5-day waves, respectively. A clear
seasonal and short-term variability are observed in the 16- and 5-day
planetary wave amplitudes. The 16-day wave reaches largest amplitude in
winter and is also present in summer, but with smaller amplitudes. The 5-day
wave reaches largest amplitude in winter and in late summer. An inter-annual
variability in the amplitude of the planetary waves is evident in the four
years of observations. Some 41 episodes of large-amplitude wave occurrence
are identified. Temperature and wind amplitudes for these episodes, AT and
AW, that passed the Student T-test were found to be related by,
AT = 0.34 AW and
AT = 0.62 AW for the 16- and 5-day
wave, respectively. |
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