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| Titel |
Jetstream and rainfall distribution in the Mediterranean region |
| VerfasserIn |
M. Gaetani, M. Baldi, G. A. Dalu, G. Maracchi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 11, no. 9 ; Nr. 11, no. 9 (2011-09-19), S.2469-2481 |
| Datensatznummer |
250009672
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| Publikation (Nr.) |
 copernicus.org/nhess-11-2469-2011.pdf |
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| Zusammenfassung |
| This is a study on the impact of the jetstream in the Euro-Atlantic region
on the rainfall distribution in the Mediterranean region; the study, based
on data analysis, is restricted to the Mediterranean rainy season, which
lasts from September to May. During this season, most of the weather systems
originate over the Atlantic, and are carried towards the Mediterranean
region by the westerly flow. In the upper troposphere of the Euro-Atlantic
region this flow is characterized by two jets: the Atlantic jet, which
crosses the ocean with a northeasterly tilt, and the African jet, which
flows above the coast of North Africa. This study shows that the cross-jet
circulation of the Atlantic jet favors storm activity in its exit
region, while the cross-jet circulation of the African jet suppresses this
kind of activity in its entrance region, with the 1st jet-stormtrack
covariance mode explaining nearly 50% of the variability. It follows that
the rainfall distribution downstream to these cross-jet circulations is
strongly influenced by their relative positions. Specifically, in fall,
rainfall is abundant in the western Mediterranean basin (WM), when the
Atlantic jet is relatively strong but its northeasterly tilt is small, and
the African jet is in its easternmost position. In winter, rainfall is
abundant in the eastern Mediterranean basin (EM); this is when the Atlantic
jet reaches the Scandinavian peninsula and the African jet is in its
westernmost position. In spring, when the two jets weaken, the Atlantic jet
retreats over the ocean, but the African jet stays in its winter position,
rainfall is abundant in the Alpine region and in the Balkans. In
addition, the covariance between precipitation and the jetstream has
been evaluated. In fall, the latitudinal displacement of the Atlantic jet
and the longitudinal displacement of the African jet modulate rainfall
anomalies in the WM, with 38% explained covariance. In winter, the
latitudinal displacement of the Atlantic jet produces rainfall anomalies in
the western and central Mediterranean, with 45% explained covariance. In
spring, the latitudinal displacement of the African jet produces rainfall
anomalies, with 38% explained covariance. |
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