Standardized Precipitation Index (SPI) evolution over the Iberian Peninsula during the 21st century

Abstract

Droughts are important natural hazards that occur worldwide and can have severe and long-lasting impacts on humans and ecosystems. These phenomena are usually quantified by means of the so-called drought indices, which are indirect indicators based on climatic information. The Standardized Precipitation Index (SPI) is one of the most widely used indexes and this study attempts to characterize the occurrence and spatial variability of this index in the Iberian Peninsula (IP) over the 21st century. The SPI was calculated at two time scales (3 and 12 months), using simulations from the EURO-CORDEX project under two future scenarios (Representative Concentration Pathway (RCP) 4.5 and RCP 8.5) to analyze meteorological and hydrological droughts. Meteorological droughts (SPI-3) are expected to be less frequent but more intense and durable in the eastern IP, intensifying throughout the century and for the RCP 8.5 scenario. In the first decades of the 21st century, hydrological droughts (SPI-12) are projected to be more common and severe in the northwestern region of the IP for the RCP 4.5, and less frequent but more lasting in the other regions of IP for the RCP 8.5. As the century passes, the drought frequency and intensity experience a decrease in the RCP 4.5 scenario, and a slight increase in the RCP 8.5 scenario.