Drought characteristic projections over the Iberian Peninsula: the effect of using nonparametric multivariate standardized drought indices

Drought is one of the most devastating natural hazards that pose significant challenges to human and ecosystems. This kind of phenomenon is expected will become more frequent and severe response to changing climate, especially in regions such as the Iberian Peninsula (IP), which is already being affected by recurring drought events. One of the most difficult challenges in assessing drought-related impacts is the lack of a universal definition of drought, consequence of the complex nature of this type of extreme phenomenon. That is, a wide range of hydrological variables are involved in the occurrence of drought events leading to different drought types, which may occur at the same time or sequentially. In this framework, multivariate drought indices were developed to address an insufficient characterization of droughts using a single variable. This study explores drought projections over the IP for different warming levels (1.5, 2, and 3ºC above pre-industrial levels) under the RCP8.5 emission scenario. For this aim, climate data from a multi-ensemble of regional climate simulations within the EURO-CORDEX initiative has been used to compute a set of multivariate standardized drought indices in their nonparametric form. Drought indicators that take into account variables such as the precipitation, soil moisture, and potential evapotranspiration have been computed for different time aggregations. Then, drought characteristics (i.e., duration, frequency, severity, intensity, and spatial extent) from the different indices have been computed in order to compare projected changes in drought conditions for this region. The findings of this work could provide valuable information to policymakers in developing drought-related adaptation and mitigation policies in response to climate change