The E‐OBS precipitation gridded data set v.10.0 is used to detect very long dry spell (VLDS) events over the entire Mediterranean Basin for the 1957–2013 period, during the wet season (September to April). The main objective is to characterize these events as climatic objects, in terms of location, spatial extent, duration, and temporal variability. In this study, 76 VLDS events were detected in the Mediterranean Basin and grouped into four spatial patterns: scattered localized (with 25 events), northeast Mediterranean (11 events), West Mediterranean (15 events), and southeast Mediterranean (25 events). Each pattern shows seasonality in events. Most of the scattered localized, northeast, and southeast events begin in September, at the beginning of the wet season. In contrast, most of the West Mediterranean events begin in the middle of the wet season. Over time, there is a slight but not significant increase in the cumulative number of days per season affected by VLDS events.

L’objectif de cette étude est d’appréhender les caractéristiques spatio-temporelles des phénomènes pluviométriques à l’échelle du bassin méditerranéen de 1950 à 2013 et notamment des évènements intenses. Les résultats montrent une baisse du cumul de pluie, durant la période de septembre à avril, quasi-généralisée à l’ensemble du bassin méditerranéen. De plus, le bassin méditerranéen connait une baisse du nombre de jours de pluie particulièrement marquée dans le nord du Portugal et de l’Algérie, au nord-est de l’Anatolie, au sud-ouest et sud-est des Balkans et sur une majeure partie de l’Italie. Dans le contexte actuel de questionnement face à l’impact du changement climatique sur la fréquence des pluies intenses en méditerranéen, il est impossible de mettre en avant une tendance significative propre à l’ensemble du bassin méditerranéen en terme de fréquence et d’intensité de ces évènements. Seuls certains secteurs tels que le sud-ouest de l’Anatolie, le sud-est et le centre-nord/nord-est des Balkans ainsi que le sud et le nord-ouest de la Péninsule Ibérique montrent une augmentation de la part des précipitations intenses dans le cumul total pour la période 1950-2013.

Flood projections are still highly uncertain, partly resulting from the limited accuracy of simulated precipitation by climate models. To overcome this limitation, recent studies suggest to use direct linkages between atmospheric processes leading precipitation, often better simulated than precipitation, and the flood occurrence. Such an approach implies, however, that historical flood events mainly result from direct contribution of precipitation only. Consequently, this paper has a twofold objective: (i) To explore to what extent the generation of medium-magnitude flood events in a large mountainous catchment can be explained by the precipitation only, and (ii) to identify what are the best features of flood-inducing precipitation episodes (i.e., duration and accumulation). Taking advantage of centennial-long discharge (gauge stations) and precipitation (ERA-20C reanalysis) data series, this study is based on three-year return period flood events of the upper Rhône River (NW European Alps). Our results suggest that half of the studied floods are triggered by precipitation only, but precipitation indices are mainly good only for high-magnitude events with return period of at least 20 years. Hence, modelling flood occurrence directly from atmospheric processes leading precipitation seems to be possible for events with the highest magnitude (i.e., the ones with the highest potential to impact societies).