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| Titel |
The climatology, propagation and excitation of ultra-fast Kelvin waves as observed by meteor radar, Aura MLS, TRMM and in the Kyushu-GCM |
| VerfasserIn |
R. N. Davis, Y.-W. Chen, S. Miyahara, 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. 4 ; Nr. 12, no. 4 (2012-02-17), S.1865-1879 |
| Datensatznummer |
250010729
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| Publikation (Nr.) |
 copernicus.org/acp-12-1865-2012.pdf |
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| Zusammenfassung |
| Wind measurements from a meteor radar on Ascension Island (8° S,
14° W) and simultaneous temperature measurements from the Aura MLS
instrument are used to characterise ultra-fast Kelvin waves (UFKW) of zonal
wavenumber 1 (E1) in the mesosphere and lower thermosphere (MLT) in the years
2005–2010. These observations are compared with some predictions of the
Kyushu-general circulation model. Good agreement is found between
observations of the UFKW in the winds and temperatures, and also with the
properties of the waves in the Kyushu-GCM. UFKW are found at periods between
2.5–4.5 days with amplitudes of up to 40 m s−1 in the zonal winds and
6 K in the temperatures. The average vertical wavelength is found to be
44 km. Amplitudes vary with latitude in a Gaussian manner with the maxima
centred over the equator. Dissipation of the waves results in monthly-mean
eastward accelerations of 0.2–0.9 m s−1 day−1 at heights around
95 km, with 5-day mean peak values of 4 m s−1 day−1. Largest
wave amplitudes and variances are observed over Indonesia and central Africa
and may be a result of very strong moist convective heating over those
regions. Rainfall data from TRMM are used as a proxy for latent-heat release
in an investigation of the excitation of these waves. No strong correlation
is found between the occurrence of large-amplitude mesospheric UFKW events
and either the magnitude of the equatorial rainfall or the amplitudes of E1
signatures in the rainfall time series, indicating that either other sources
or the propagation environment are more important in determining the
amplitude of UFKW in the MLT. A strong semiannual variation in wave
amplitudes is observed. Intraseasonal oscillations (ISOs) with periods 25–60
days are evident in the zonal background winds, zonal-mean temperature, UFKW
amplitudes, UFKW accelerations and the rainfall rate. This suggests that UFKW
play a role in carrying the signature of tropospheric ISOs to the MLT region. |
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