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| Titel |
Polar mesosphere summer echoes: a comparison of simultaneous observations at three wavelengths |
| VerfasserIn |
E. Belova, P. Dalin, S. Kirkwood  |
| 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 ; 25, no. 12 ; Nr. 25, no. 12 (2008-01-02), S.2487-2496 |
| Datensatznummer |
250015955
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2487-2007.pdf |
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| Zusammenfassung |
| On 5 July 2005, simultaneous observations of Polar Mesosphere Summer Echoes
(PMSE) were made using the EISCAT VHF (224 MHz) and UHF (933 MHz) radars
located near Tromsø, Norway and the ALWIN VHF radar (53.5 MHz) situated
on Andøya, 120 km SW of the EISCAT site. During the short interval from
12:20 UT until 12:26 UT strong echoes at about 84 km altitude were detected
with all three radars. The radar volume reflectivities were found to be
4×10−13 m−1, 1.5×10−14 m−1 and 1.5×10−18 m−1 for the ALWIN, EISCAT-VHF and UHF radars, respectively.
We have calculated the reflectivity ratios for each pair of radars and have
compared them to ratios obtained from the turbulence-theory model proposed
by Hill (1978a). We have tested different values of the turbulent energy
dissipation rate ε and Schmidt number Sc, which are free
parameters in the model, to try to fit theoretical reflectivity ratios to
the experimental ones. No single combination of the parameters ε and Sc could be found to give a good fit. Spectral widths for the
EISCAT radars were estimated from the spectra computed from the
autocorrelation functions obtained in the experiment. After correction for
beam-width broadening, the spectral widths are about 4 m/s for the
EISCAT-VHF and 1.5–2 m/s for the UHF radar. However, according to the
turbulence theory, the spectral widths in m/s should be the same for both
radars. We also tested an incoherent scatter (IS) model developed by Cho et
al. (1998), which takes into account the presence of charged aerosols/dust
at the summer mesopause. It required very different sizes of particles for
the EISCAT-VHF and UHF cases, to be able to fit the experimental spectra
with model spectra. This implies that the IS model cannot explain PMSE
spectra, at least not for monodisperse distributions of particles. |
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