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| Titel |
Trends in the characteristics of the annual and semiannual variations observed in the radio wave absorption in the lower ionosphere |
| VerfasserIn |
J. Laštovička, D. Pancheva |
| 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 ; 17, no. 10 ; Nr. 17, no. 10, S.1336-1343 |
| Datensatznummer |
250013827
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1336-1999.pdf |
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| Zusammenfassung |
The continuous increase in concentration of
greenhouse gases in the atmosphere is expected to cool higher levels of the
atmosphere. There is some direct and indirect experimental evidence of long-term
trends in temperature and other parameters in the mesosphere and lower
thermosphere (MLT). Here we look for long-term trends in the annual and
semiannual variations of the radio wave absorption in the lower ionosphere,
which corresponds to the MLT region heights. Data from central and southeastern
Europe are used. A consistent tendency to a positive trend in the amplitude of
the semiannual wave appears to be observed. The reality of a similar tendency in
the amplitude of the annual wave is questionable in the sense that the trend in
the amplitude of the annual wave is probably induced by the trend in the yearly
average values of absorption. The phases of both the annual and semiannual waves
display a forward tendency, i.e. shift to an earlier time in the year. A
tentative interpretation of these results in terms of changes of the seasonal
variation of temperature and wind at MLT heights does not contradict the trends
observed in those parameters.
Key words. Ionosphere (ionosphere – atmosphere
interactions; mid-latitude ionosphere) · Meteorology and atmospheric dynamics
(middle atmosphere dynamics) |
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