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| Titel |
Five-day planetary waves in the middle atmosphere from Odin satellite data and ground-based instruments in Northern Hemisphere summer 2003, 2004, 2005 and 2007 |
| VerfasserIn |
A. Belova, S. Kirkwood  , D. Murtagh, N. Mitchell, W. Singer, W. Hocking |
| 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 ; 26, no. 11 ; Nr. 26, no. 11 (2008-11-17), S.3557-3570 |
| Datensatznummer |
250016293
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3557-2008.pdf |
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| Zusammenfassung |
| A number of studies have shown that 5-day planetary waves modulate
noctilucent clouds and the closely related Polar Mesosphere Summer Echoes
(PMSE) at the summer mesopause. Summer stratospheric winds should inhibit
wave propagation through the stratosphere and, although some numerical
models (Geisler and Dickinson, 1976) do show a possibility for upward wave
propagation, it has also been suggested that the upward propagation may in
practice be confined to the winter hemisphere with horizontal propagation of
the wave from the winter to the summer hemisphere at mesosphere heights
causing the effects observed at the summer mesopause. It has further been
proposed (Garcia et al., 2005) that 5-day planetary waves observed in the
summer mesosphere could be excited in-situ by baroclinic instability in the
upper mesosphere. In this study, we first extract and analyze 5-day
planetary wave characteristics on a global scale in the middle atmosphere
(up to 54 km in temperature, and up to 68 km in ozone concentration) using
measurements by the Odin satellite for selected days during northern
hemisphere summer from 2003, 2004, 2005 and 2007. Second, we show that 5-day
temperature fluctuations consistent with westward-traveling 5-day waves are
present at the summer mesopause, using local ground-based meteor-radar
observations. Finally we examine whether any of three possible sources of
the detected temperature fluctuations at the summer mesopause can be
excluded: upward propagation from the stratosphere in the summer-hemisphere,
horizontal propagation from the winter-hemisphere or in-situ excitation as a
result of the baroclinic instability. We find that in one case, far from
solstice, the baroclinic instability is unlikely to be involved. In one
further case, close to solstice, upward propagation in the same hemisphere
seems to be ruled out. In all other cases, all or any of the three proposed
mechanisms are consistent with the observations. |
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