Abstract
Abstract. Assessing the probability of occurrence of drought is important for improving current drought assessment, management and mitigation measures, and strategies across Spain. This study employed two well-established drought indices, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), to characterize drought duration and magnitude at different timescales over Spain. In order to map the drought hazard probability, we applied the extreme value theory and tested different thresholds to generate peak-over-threshold (POT) drought duration and magnitude series. Our results demonstrate that the generalized Pareto (GP) distribution performs well in estimating the frequencies of drought magnitude and duration. Specifically, we found a good agreement between the observed and modelled data when using upper percentiles to generate the POT series. Spatially, our estimations suggest a higher probability of extreme drought events in southern and central Spain compared to the northern and eastern regions. Also, our study found spatial differences in drought probability estimations as a function of the selected drought index (i.e. SPI vs. SPEI) and timescale (i.e. 1, 3, 6, and 12 months). Drought hazard probability maps can contribute to the better management of different sectors (e.g. agriculture, water resources management, urban water supply, and tourism) at national, regional, and even local scale in Spain.
Highlights
Drought is one of the main hydroclimatic hazards in Spain, with adverse impacts on natural and human environments (Pérez and Barreiro-Hurlé, 2009; UNEP, 2006)
At low percentiles, the points do not approximate to the theoretical curve of the generalized Pareto (GP) distribution, but they tend to approximate to the GP curve at percentiles between 60th and 80th
The series of drought magnitude show a better fit to GP distribution than those of drought duration, but with no considerable differences between Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI)
Summary
Drought is one of the main hydroclimatic hazards in Spain, with adverse impacts on natural and human environments (Pérez and Barreiro-Hurlé, 2009; UNEP, 2006). Current national measures are quite useful to diminish drought risk, other improved approaches are still desired to reduce drought risk, for real-time drought monitoring Mishra et al, 2009; Mishra and Singh, 2011) In this context, drought probability maps can be a promising tool to characterize drought risk at a detailed spatial scale. Due to the availability of dense spatial climate data, there is a possibility to map drought probability at a fine spatial scale.
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