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OSUG - Terre Univers Environnement

Winter time Very Long Dry Spells over the Mediterranean Basin: detection and associated atmospheric dynamics

Séminaire de Florian RAYMOND (CRC), vendredi 30 juin 2017 à 14 h, salle 105 OSUG-B

by Sandra Rome - 20 June 2017

Title: Winter time Very Long Dry Spells over the Mediterranean Basin: detection and associated atmospheric dynamics

Abstract: Mediterranean wintertime precipitations (September to April) are important for annual water resources, summer ground moisture, vegetation and agriculture. Long period without precipitation during this season may cause many environmental and social impacts. The study focuses on the identification of very long dry spells (VLDS) in the Mediterranean region and their spatio-temporal variability in actual (1957-2013) and future (1961-2100) climate. VLDS patterns are associated with anticyclonic conditions, located about 1000km north-west of the area experiencing drought conditions, which lead blocking high and large scale subsidence of the cold air flow, coming from northern latitude. There is some control of Euro-Atlantic weather regimes (WR) on the VLDS: “NAO+” WR promote the VLDS in the western Mediterranean and “Atlantic Ridge” is associated with WR in the Eastern Mediterranean. It seems that a long sequence of consecutive days of these WR favours the occurrence of VLDS events. Med-CORDEX regional models accurately reproduce the occurrence of VLDS (more than 70% of the observed VLDS are found in the evaluation simulations). The models also well reproduce the VLDS spatio-temporal characteristics (i.e. location, spatial extension and duration). These regional models show that VLDS would be longer and larger during the 21st century, especially with the RCP 8.5 scenario. CMIP5 multi-models analysis does not show specific trends of WR frequency and sequences duration in future climate. Nevertheless, significant positive trends of mean sea level pressure (SLP) in the central Mediterranean basin during winter could reinforce VLDS events during the 21st century.

RAYMOND F. (1), ULLMANN A. (1), CAMBERLIN P. (1), DROBINSKI P. (2)

(1) Centre de Recherches de Climatologie, UMR6282 Biogéosciences, CNRS, Dijon, France.
(2) Laboratoire de Météorologie Dynamique, Institut Pierre Simon Laplace, CNRS, Ecole Polytechnique, Université Pierre et Marie Curie, Palaiseau and Paris, France.

florian.raymond@u-bourgogne.fr ; albin.ullmann@u-bourgogne.fr ; pierre.camberlin@u-bourgogne.fr ; philippe.drobinski@lmd.polytechnique.fr





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