Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmosres Spatial and temporal analysis of drought variability at several time scales in Syria during 1961–2012 Shifa Mathbout a,b,⁎ , Joan A. Lopez-Bustins b , Javier Martin-Vide b , Joan Bech a , Fernando S. Rodrigo c a Department of Applied Physics-Meteorology, University of Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain b Climatology Group, Department of Geography, University of Barcelona, Montalegre 6, 08001 Barcelona, Spain c Department of Chemistry and Physics, University of Almeria, Spain ARTICLE INFO Keywords: Climate regionalization Drought SPEI SPI Syrian conflict ABSTRACT This paper analyses the observed spatiotemporal characteristics of drought phenomenon in Syria using the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Temporal variability of drought is calculated for various time scales (3, 6, 9, 12, and 24 months) for 20 weather stations over the 1961–2012 period. The spatial patterns of drought were identified by applying a Principal Component Analysis (PCA) to the SPI and SPEI values at different time scales. The results revealed three het- erogeneous and spatially well-defined regions with different temporal evolution of droughts: 1) Northeastern (inland desert); 2) Southern (mountainous landscape); 3) Northwestern (Mediterranean coast). The evolutionary characteristics of drought during 1961–2012 were analysed including spatial and temporal variability of SPI and SPEI, the frequency distribution, and the drought duration. The results of the non-parametric Mann–Kendall test applied to the SPI and SPEI series indicate prevailing significant negative trends (drought) at all stations. Both drought indices have been correlated both on spatial and temporal scales and they are highly comparable, especially, over a 12 and 24 month accumulation period. We concluded that the temporal and spatial char- acteristics of the SPI and SPEI can be used for developing a drought intensity - areal extent - and frequency curve that assesses the variability of regional droughts in Syria. The analysis of both indices suggests that all three regions had a severe drought in the 1990s, which had never been observed before in the country. Furthermore, the 2007–2010 drought was the driest period in the instrumental record, happening just before the onset of the recent conflict in Syria. 1. Introduction Drought is one of the most complicated and recurring natural ha- zards which has different impacts on ecological, economic, social, agricultural, cultural and political areas in almost all climatic regions especially in rain-fed agricultural regions (Kastopoulou et al., 2017; Surendran et al., 2017) with varying frequency, severity and duration (Van Loon, 2015; Deo and Sahin, 2015; Deo et al., 2017). Precipitation is a major parameter for studying hydrological and meteorological variables (Lo Conti et al., 2014; Wang et al., 2016), managing water resources (Retalis et al., 2016; Awchi and Kalyana, 2017) and detecting some natural hazards as drought (Zambrano et al., 2017). Drought can be characterized in multiple ways (Heim, 2002; Keyantash and Dracup, 2002) and can be defined as a natural recurrent feature of the climate cycle occurring in different climatic zones which is generally perceived to be a prolonged period with significantly lower precipitation relative to normal levels or increased evaporative demand or a combination of both of them. It is a three dimensional complex natural hazard characterized by severity (magnitude or intensity), duration and areal extent (Tsakiris et al., 2007; Vicente-Serrano et al., 2010a, 2012; Mohammed and Scholz, 2017) which may be studied from the environmental or the water resource point of view (Wilhite and Glantz, 1985). The observed impact of climate system changes on droughts varies regionally, based on changes of the drought drivers such as precipitation and temperature and on regional features of the hydro-climate modelling system (Sheffield and Wood, 2008; McCabe and Wolock, 2015). Based on the nature of the water deficit, four types of droughts are defined: meteorological, hydrological, agricultural and socio-economical (Wilhite and Glantz, 1985; Martín Vide and Olcina, 2001; AMS, 2004). The spatial patterns of droughts are generally very complex (Vicente-Serrano, 2006) and the differences in these patterns are big in climatic transition areas as the Mediterranean basin, because http://dx.doi.org/10.1016/j.atmosres.2017.09.016 Received 29 May 2017; Received in revised form 18 September 2017; Accepted 26 September 2017 ⁎ Corresponding author at: Climatology Group, Department of Geography, University of Barcelona, Montalegre 6, 08001 Barcelona, Spain. E-mail address: shifa.mathbout@ub.edu (S. Mathbout). Atmospheric Research 200 (2018) 153–168 Available online 29 September 2017 0169-8095/ © 2017 Elsevier B.V. All rights reserved. MARK