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| Titel |
Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns |
| VerfasserIn |
A. Toreti, E. Xoplaki, D. Maraun, F. G. Kuglitsch, H. Wanner, J. Luterbacher |
| 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 ; 10, no. 5 ; Nr. 10, no. 5 (2010-05-20), S.1037-1050 |
| Datensatznummer |
250008154
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| Publikation (Nr.) |
 copernicus.org/nhess-10-1037-2010.pdf |
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| Zusammenfassung |
| We present an analysis of daily extreme precipitation events for the extended
winter season (October–March) at 20 Mediterranean coastal sites covering the
period 1950–2006. The heavy tailed behaviour of precipitation extremes and
estimated return levels, including associated uncertainties, are derived
applying a procedure based on the Generalized Pareto Distribution, in
combination with recently developed methods. Precipitation extremes have an
important contribution to make seasonal totals (approximately 60% for all
series). Three stations (one in the western Mediterranean and the others in
the eastern basin) have a 5-year return level above 100 mm, while the lowest
value (estimated for two Italian series) is equal to 58 mm. As for the
50-year return level, an Italian station (Genoa) has the highest value of
264 mm, while the other values range from 82 to 200 mm. Furthermore, six
series (from stations located in France, Italy, Greece, and Cyprus) show a
significant negative tendency in the probability of observing an extreme
event. The relationship between extreme precipitation events and the large
scale atmospheric circulation at the upper, mid and low troposphere is
investigated by using NCEP/NCAR reanalysis data. A 2-step classification
procedure identifies three significant anomaly patterns both for the
western-central and eastern part of the Mediterranean basin. In the western
Mediterranean, the anomalous southwesterly surface to mid-tropospheric flow
is connected with enhanced moisture transport from the Atlantic. During
≥5-year return level events, the subtropical jet stream axis is aligned
with the African coastline and interacts with the eddy-driven jet stream.
This is connected with enhanced large scale ascending motions, instability
and leads to the development of severe precipitation events. For the eastern
Mediterranean extreme precipitation events, the identified anomaly patterns
suggest warm air advection connected with anomalous ascent motions and an
increase of the low- to mid-tropospheric moisture. Furthermore, the jet
stream position (during ≥5-year return level events) supports the eastern
basin being in a divergence area, where ascent motions are favoured. Our
results contribute to an improved understanding of daily precipitation
extremes in the cold season and associated large scale atmospheric features. |
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