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| Titel |
NLC and the background atmosphere above ALOMAR |
| VerfasserIn |
J. Fiedler, G. Baumgarten, U. Berger, P. Hoffmann, N. Kaifler, F.-J. Lübken |
| 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 ; 11, no. 12 ; Nr. 11, no. 12 (2011-06-21), S.5701-5717 |
| Datensatznummer |
250009854
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| Publikation (Nr.) |
 copernicus.org/acp-11-5701-2011.pdf |
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| Zusammenfassung |
| Noctilucent clouds (NLC) have been measured by the Rayleigh/Mie/Raman-lidar
at the ALOMAR research facility in Northern Norway (69° N,
16° E). From 1997 to 2010 NLC were detected during more than 1850 h
on 440 different days. Colocated MF-radar measurements and calculations
with the Leibniz-Institute Middle Atmosphere (LIMA-) model are used to
characterize the background atmosphere. Temperatures as well as horizontal
winds at 83 km altitude show distinct differences during NLC observations
compared to when NLC are absent. The seasonally averaged temperature is lower
and the winds are stronger westward when NLC are detected. The wind
separation is a robust feature as it shows up in measurements as well as in
model results and it is consistent with the current understanding that lower
temperatures support the existence of ice particles. For the whole 14-year
data set there is no statistically significant relation between NLC
occurrence and solar Lyman-α radiation. On the other hand NLC
occurrence and temperatures at 83 km show a significant anti-correlation,
which suggests that the thermal state plays a major role for the existence of
ice particles and dominates the pure Lyman-α influence on water vapor
during certain years. We find the seasonal mean NLC altitudes to be
correlated to both Lyman-α radiation and temperature. NLC above ALOMAR
are strongly influenced by atmospheric tides. The cloud water content varies
by a factor of 2.8 over the diurnal cycle. Diurnal and semidiurnal amplitudes
and phases show some pronounced year-to-year variations. In general,
amplitudes as well as phases vary in a different manner. Amplitudes change by
a factor of more than 3 and phases vary by up to 7 h. Such variability
could impact long-term NLC observations which do not cover the full diurnal
cycle. |
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