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| Titel |
A study on natural and manmade global interannual fluctuations of cirrus cloud cover for the period 1984-2004 |
| VerfasserIn |
K. Eleftheratos, C. S. Zerefos, P. Zanis, D. S. Balis, G. Tselioudis, K. Gierens, R. Sausen |
| 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 ; 7, no. 10 ; Nr. 7, no. 10 (2007-05-21), S.2631-2642 |
| Datensatznummer |
250004992
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| Publikation (Nr.) |
 copernicus.org/acp-7-2631-2007.pdf |
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| Zusammenfassung |
| The seasonal variability and the interannual variance explained by ENSO and
NAO to cirrus cloud cover (CCC) are examined during the twenty-year period
1984–2004. CCC was found to be significantly correlated with vertical
velocities and relative humidity from ECMWF/ERA40 in the tropics
(correlations up to −0.7 and +0.7 at some locations, respectively)
suggesting that variations in large-scale vertical winds and relative
humidity fields can be the origin of up to half of the local variability in
CCC over these regions. These correlations reflect mostly the seasonal
cycle. Although the annual cycle is dominant in all latitudes and
longitudes, peaking over the tropics and subtropics, its amplitude can be
exceeded during strong El Nino/La Nina events. Over the eastern tropical
Pacific Ocean the interannual variance of CCC which can be explained by ENSO
is about 6.8% and it is ~2.3 times larger than the amplitude of the
annual cycle. Natural long-term trends in the tropics are generally small
(about −0.3% cloud cover per decade) and possible manmade trends in
those regions are also small. The contributions of NAO and QBO to the
variance of CCC in the tropics are also small. In the northern
mid-latitudes, on the other hand, the effect of NAO is more significant and
can be very important regionally. Over northern Europe and the eastern part
of the North Atlantic Flight Corridor (NAFC) there is a small positive
correlation between CCC and NAO index during the wintertime of about 0.3. In
this region, the interannual variance of CCC explained by NAO is 2.6% and
the amplitude of the annual cycle is 3.1%. Long-term trends over this
region are about +1.6% cloud cover per decade and compare well with the
observed manmade trends over congested air traffic regions in Europe and the
North Atlantic as have been evidenced from earlier findings. |
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