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| Titel |
An alternative explanation of PMSE-like scatter in MF radar data |
| VerfasserIn |
G. O. L. Jones, M. A. Clilverd, P. J. Espy, S. Chew, D. C. Fritts, D. M. Riggin |
| 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 ; 22, no. 8 ; Nr. 22, no. 8 (2004-09-07), S.2715-2722 |
| Datensatznummer |
250014958
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| Publikation (Nr.) |
 copernicus.org/angeo-22-2715-2004.pdf |
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| Zusammenfassung |
| There have been reports in the literature that spaced-antenna MF radars may
provide a source of data on Polar Mesospheric Summer Echoes (PMSE). Even
though the expected scatter from PMSE at MF frequencies is very much weaker
than at VHF, the wide distribution of sites and long duration of data sets
for MF radar systems could provide valuable information about the occurrence
of PMSE. This paper tests whether there is any evidence of PMSE in the
profiles derived using the MF radar at Rothera, Antarctica, one of the few
such radars at high southern latitudes. Over a year of data during 1997/1998
has been analysed for the occurrence of persistent features around midday in
the altitude range 60-95km. Criteria were chosen to test the likelihood
that some of the narrow peaks in the power profiles were manifestations of
electron density structures associated with PMSE. Although a small number of
persistent features were seen at altitudes of 80-85km that are typically
associated with PMSE, there was no seasonality in their occurrence. A
detailed analysis of specific days showed that two peaks were often seen
with altitude separations consistent with the vertical wavelength of the
diurnal tide. Persistent features were also detected at altitudes of 70km
and 90km during the winter months, thus showing a quite different
seasonality to that of PMSE. An estimate of the turbulence caused by the
breaking of gravity waves that have propagated up from the lower atmosphere
shows that at Rothera significant energy is deposited near 80km during
summer, and near 70 and 90km during winter. This seasonal variability is
driven by the screening effect of stratospheric winds, and it appears that
breaking gravity wave dynamics, rather than PMSE phenomena, can explain many
of the localised altitude features in the MF radar data. |
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