LB 7-55 - Climate change and drought evolution in Spain, 1916-2015

Drought is the most devastating natural hazard in terms of its spatial extent, duration, and potential to affect whole regions of the world. Its impacts are first noticed in the natural and agro-ecosistems but are rapidly expanded towards other economic sectors, ultimately affecting the whole society specially in less developed countries. Despite its importance, up to now there is little knowledge of the mechanisms that drive drought onset and evolution. One possible way of studying droughts is by developing a catalogue of past episodes and studying their progressive development and the atmospheric mechanisms that played a role. Here, we leveraged on the longest and most dense data base of monthly precipitation and temperature over mainland Spain covering 1916-2020, previously developed by our team, to study the largest drought episodes over the last century. We computed a data set of drought indices (SPI, SPEI) to determine the largest drought events of the last century for further analysis. Each event was assessed in terms of its temporal variability considering short and long-scale of the drought indices and their spatial evolution, and were characterised by their integral magnitudes (intensity, duration). Principal components analysis was used to find the main spatial configurations of drought over the study area. Finally, each spatial component was related to their main atmospheric drivers. As a result, we elaborated a catalogue of drought events in Spain over the last century, and to infer several characteristic types. The longest and most intense episodes, though, were usually characterised by a complex behaviour with a succession of more than one type.