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., Project PID2020-116860RB-C22: Extremos térmicos y pluviométricos en la España peninsular 1916-2020), funded by the Spanish Ministry of Science., Peer reviewed