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| Titel |
Origin of the moisture feeding the Heavy Precipitating Systems over Southeastern France |
| VerfasserIn |
F. Duffourg, V. Ducrocq |
| 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. 4 ; Nr. 11, no. 4 (2011-04-27), S.1163-1178 |
| Datensatznummer |
250009348
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| Publikation (Nr.) |
 copernicus.org/nhess-11-1163-2011.pdf |
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| Zusammenfassung |
In the Northwestern Mediterranean region, large amounts of precipitation can
accumulate over the coasts in less than a day. The present study aims at
characterising the origin and the pathways of the moisture feeding such heavy
precipitation. The ten Heavy Precipitating Events (HPEs) that occurred over
the French Mediterranean region during the autumns of 2008 and 2009 are
simulated with the non-hydrostatic research numerical model Meso-NH at
2.5 km, 10 km and 40 km horizontal resolution.
Using eulerian on-line passive tracers, high-resolution simulations (2.5 km
horizontal resolution) show that the heavy precipitating systems are fed by a
south-southwesterly to easterly low-level moist flow. It is typically 1000 m
deep and remains almost unchanged all along an event. This low-level feeding
flow crosses the most northwestern part of the Mediterranean in 5 to 10 h.
Larger-scale simulations (40 km and 10 km horizontal resolution) show that
the moisture of the low-level feeding flow is provided by both evaporation of
the Mediterranean Sea within the last 2 days before the HPE triggering and
transport from remote sources in the lower half of the troposphere over more
than 3 to 4 days. Local Mediterranean moisture is gained along the air mass
low-level progress towards the Northwestern Mediterranean basin following two
main branches along the Spanish coast and west of Sardinia. The Mediterranean
Sea is the main moisture source when anticyclonic conditions prevail during
the last 3 or 4 days before the HPE. When cyclonic conditions prevail before
the HPE, the relative contribution of local and remote sources is more
balanced. Remote moisture comes most of the time from the Atlantic Ocean.
African tropical moisture is a less frequent but larger remote source. |
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