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| Titel |
Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data |
| VerfasserIn |
X. Xu, A. H. Manson, C. E. Meek, T. Chshyolkova, J. R. Drummond, C. M. Hall, D. M. Riggin, R. E. Hibbins |
| 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 ; 27, no. 9 ; Nr. 27, no. 9 (2009-09-01), S.3387-3409 |
| Datensatznummer |
250016637
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| Publikation (Nr.) |
 copernicus.org/angeo-27-3387-2009.pdf |
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| Zusammenfassung |
The coupling processes in the middle atmosphere have been a subject of
intense research activity because of their effects on atmospheric
circulation, structure, variability, and the distribution of chemical
constituents. In this study, the day-to-day variability of Aura-MLS
(Microwave Limb Sounder) temperature data are used to reveal the vertical
and interhemispheric coupling processes in the stratosphere-mesosphere
during four Northern Hemisphere winters (2004/2005–2007/2008). The UKMO (United
Kingdom Meteorological Office) assimilated data and mesospheric winds from
MF (medium frequency) radars are also applied to help highlight the coupling
processes.
In this study, a clear vertical link can be seen between the stratosphere
and mesosphere during winter months. The coolings and reversals of northward
meridional winds in the polar winter mesosphere are often observed in
relation to warming events (Sudden Stratospheric Warming, SSW for short) and
the associated changes in zonal winds in the polar winter stratosphere. An
upper-mesospheric cooling usually precedes the beginning of the warming in
the stratosphere by 1–2 days.
Inter-hemispheric coupling has been identified initially by a correlation
analysis using the year-to-year monthly zonal mean temperature. Then the
correlation analyses are performed based upon the daily zonal mean
temperature. From the original time sequences, significant positive
(negative) correlations are generally found between zonal mean temperatures
at the Antarctic summer mesopause and in the Arctic winter stratosphere
(mesosphere) during northern mid-winters, although these correlations are
dominated by the low frequency variability (i.e. the seasonal trend). Using
the short-term oscillations (less than 15 days), the statistical result, by
looking for the largest magnitude of correlation within a range of time-lags
(0 to 10 days; positive lags mean that the Antarctic summer mesopause is
lagging), indicates that the temporal variability of zonal mean temperature
at the Antarctic summer mesopause is also positively (negatively) correlated
with the polar winter stratosphere (mesosphere) during three (2004/2005,
2005/2006, and 2007/2008) out of the four winters. The highest value of the
correlation coefficient is over 0.7 in the winter-stratosphere for the three
winters. The remaining winter (2006/2007) has more complex correlations
structures; correspondingly the polar vortex was distinguished this winter.
The time-lags obtained for 2004/2005 and 2006/2007 are distinct from 2005/2006 and
2007/2008 where a 6-day lag dominates for the coupling between the winter
stratosphere and the summer mesopause. The correlations are also provided
using temperatures in northern longitudinal sectors in a comparison with the
Antarctic-mesopause zonal mean temperature. For northern mid-high latitudes
(~50–70° N), temperatures in Scandinavia-Eastern Europe and in the
Pacific-Western Canada longitudinal sectors often have opposite signs of
correlations with zonal mean temperatures near the Antarctic summer
mesopause during northern mid-winters. The statistical results are shown to
be associated with the Northern Hemisphere's polar vortex characteristics. |
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