Les risques climatiques liés aux changements en cours dans la dynamique des masses d'air sur l'Europe Occidentale

The research program about the " air-mass dynamics and climate-related risks over Western Europe " was supported by the MAIF Foundation over the 2008-2010 period. The impacts of the large-scale circulation patterns on rainfall / risings or floods, spring frost events and doughts were analysed using the the Objective Grosswetterlagen Catalogue adapted from the Hess-Brezowsky (HB) classification of circulation patterns. The studied areas were especially located in the northern and western part of France. The first results showed the reliability and the usefullness of the HB classification in Western France. Over all the available period (1850-2009), statistical analysis carried out by major types (GWT) and subtypes (GWL) of circulation patterns pointed out some significant trends. The space-time distribution of the impacts of circulation patterns on temperature and precipitation displays differences due to the continentality and some small-scale geographical factors.