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| Titel |
Stratosphere/mesosphere coupling during the winter/summer transition at Davis, Antarctica |
| VerfasserIn |
Franz-Josef Lübken, Josef Höffner, Timo P. Viehl, Erich Becker, Ralph Latteck, Bernd Kaifler, Ray J. Morris |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102530
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| Publikation (Nr.) |
 EGU/EGU2015-1853.pdf |
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| Zusammenfassung |
| The mobile scanning iron lidar of the Leibniz Institute of Atmospheric Physics in
Kühlungsborn (IAP) was in operation at Davis, Antarctica, from December 15, 2010, until
December 31, 2012. It measured iron densities, vertical winds, and temperatures in the iron
layer, i.Âe.Âfrom approximately 80 to 100 km. The measurement principle is based on
probing the Doppler broadened resonance line of iron atoms at 386 nm. The lidar can operate
under daylight conditions. Typical values for temperature uncertainty, altitude and time
resolution are 3-5 K, 1 km, and 1 hour, respectively. At Davis, the lidar has achieved at total
of 2900 hours of temperature measurements which is presumably the largest nearly
continuous data set in Antarctica. In this presentation we concentrate on the winter/summer
transition in three consecutive years and compare with circulation changes in the stratosphere
derived from MERRA (NASA’s Modern-Era Retrospective analysis for Research
and Applications). We also compare with the northern hemisphere (NH). We find
that the thermal structure around the mesopause at Davis is closely coupled to the
general circulation in the stratosphere, more precisely to the transition from winter to
summer conditions. In contrast to theoretical expectations we occasionally find the
mesopause significantly higher and colder(!) compared to the NH. The mesopause
altitude changes by several kilometers throughout the summer season, which is
significantly different from the summer in the northern hemispheric. Depending on
altitude, temperatures can be warmer or colder compared to the NH summer. The
Australian Antarctic Division has been operating a 55 MHz VHF radar at Davis since
February 2003. We have studied the seasonal variation of polar mesosphere summer
echoes (PMSE). PMSE are strong radar echoes related to ice particles and therefore
require atmospheric temperatures lower than the frost point temperature. We note
that (apart from low temperatures) more ingredients are required for PMSE, for
example, background electrons and neutral air turbulence. The VHF radar at Davis
(69°S) frequently detected PMSE. We compare the seasonal variation of PMSE with
stratospheric circulation, both at Davis and at ALOMAR (69°N). We present model
calculations applying the Kühlungsborn Mechanistic Circulation Model (KMCM)
to facilitate the interpretation of the stratosphere/mesosphere coupling during the
winter/summer transition, and the difference between the southern and the northern
hemisphere. |
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