Co-Occurrence of Extreme Daily Rainfall in the French Mediterranean Region

We propose in this article a statistical framework to study local disparities in the co-occurrence of extreme rainfall in the French Mediterranean region. We employ a region-of-influence approach by studying the likelihood of the 3% largest daily rainfall to occur simultaneously at less than 50 km distance, when moving across the region. Our model uses an anisotropic max-stable process allowing us to properly represent the co-occurrence of daily extremes and including the possibility of a preferred direction of co-occurrence. We use this framework on a dense network composed of almost 900 daily stations spread over a 100,000 km(2) region of southern France under a Mediterranean influence, with data back to 1948. This density allows us to study the spatial patterns in the co-occurrence of extreme rainfall at fine scale and by so to characterize the main precipitation systems leading to extremes in the region. We show in particular that concomitant extremes are the most likely along the crest line of the Massif Central, which is also the area where the magnitude of extremes is among the largest. This may be of concern for flood risk management.