Abstract
The purpose of this research was to identify major drought events on the Spanish mainland between 1961 and 2014 by means of two drought indices, and analyze the spatial propagation of drought conditions. The indices applied were the standardized precipitation index (SPI) and the standardized evaporation precipitation index (SPEI). The first was calculated as standardized anomalies of precipitation at various temporal intervals, while the second examined the climatic balance normalized at monthly scale, incorporating the relationship between precipitation and the atmospheric water demand. The daily meteorological data from Spanish Meteorological Archives (AEMet) were used in performing the analyses. Within the framework of the DESEMON project, original data were converted into a high spatial resolution grid (1.1 km2) following exhaustive quality control. Values of both indices were calculated on a weekly scale and different timescales (12, 24 and 36 months). The results show that during the first half of the study period, the SPI usually returned a higher identification of drought areas, while the reverse was true from the 1990s, suggesting that the effect from atmospheric evaporative demand could have increased. The temporal propagation from 12- to 24-month and 36-month timescales analyzed in the paper seems to be a far from straightforward phenomenon that does not follow a simple rule of time lag, because events at different temporal scales can overlap in time and space. Spatially, the propagation of drought events affecting more than 25% of the total land indicates the existence of various spatial gradients of drought propagation, mostly east–west or west–east, but also north–south have been found. No generalized episodes were found with a radial pattern, i.e., from inland to the coast.
Highlights
Drought is one of the climate hazards that causes many negative impacts on natural and socioeconomic systems (Stahl et al 2015, 2016; Van Loon et al 2016)
Droughts in Spain have very different dimensions, affecting agriculture, forests and the frequency of wild fires, but currently the most important impacts relate to the hydrological dimension, which may cause heavy losses in highly productive irrigated agriculture, reduce hydropower production, and cause problems for industry and the water supply (Jerez et al 2013; Lorenzo-Lacruz et al 2010, 2013)
We identified a total of 15 major drought episodes in which at least 25% of land was under the drought conditions defined by an standardized evaporation precipitation index (SPEI) value of \ - 1.28
Summary
Drought is one of the climate hazards that causes many negative impacts on natural and socioeconomic systems (Stahl et al 2015, 2016; Van Loon et al 2016). Spain drought analysis is not an easy task, as it is quite difficult to accurately determine the spatial and temporal dimensions of drought events (Wilhite and Glantz 1985; Lloyd-Hughes 2014; Vicente-Serrano 2016) For this reason, synthetic tools—the drought indices–have been developed, mostly based on the climate information (e.g., Heim 2002; Keyantash and Dracup 2002). Some studies have suggested that the Spanish mainland has witnessed an increased severity in droughts over the last few decades (Hoerling et al 2012; VicenteSerrano et al 2014a), causing heavy environmental, agricultural and economic impacts (e.g., Camarero et al 2015; Pascoa et al 2017) This suggests that drought management plans should be put in place to cope with the risk more efficiently (Maia and Vicente-Serrano 2017)
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