Variabilité spatio-temporelle des séquences sèches en France depuis 1950

Abstract

This work proposes the study of spatial and temporal variability of rainfall droughts (no rain) on the scale of metropolitan France since the 1950s and for each of the four seasons (spring, summer, autumn, winter). A dry period approach makes it possible to understand the intrinsic spatio-temporal characteristics: geography, seasonality, duration and frequency. In spring and autumn, the increase in the number of dry spells seems to be offset by the decrease in their average duration (and vice versa). The summer season, which is the driest season, has seen an increase in the number of dry days over most of the territory, mainly due to the increase in the average duration of dry spells and the number of the longest of them. In winter, the north of France is subject to an increase in the number of dry spells as well as the duration of the longest ones, leading to an increase in the total number of dry days. This study shows that an absence of clear and significant trends in the number of dry days in France does not necessarily mean that the temporal distribution of precipitation has not changed. An absence of trends in the number of dry days may hide an increase in the duration of the dry periods but a decrease in the number of these periods, or vice versa. These different modes of spatio-temporal variability in the absence of rain are all suitable scales for impact studies, particularly on economic activities dependent on the water cycle.

Keywords

• drought
• climate change
• climate variability