Spatial Patterns and Temporal Variability of Drought in Western Iran |
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Authors: | Tayeb Raziei Bahram Saghafian Ana A. Paulo Luis S. Pereira Isabella Bordi |
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Affiliation: | (1) Soil Conservation and Watershed Management Research Institute (SCWMRI), Tehran, Iran;(2) Agricultural Engineering Research Center, Institute of Agronomy, Technical University of Lisbon, Tapada da Ajuda, Lisbon, Portugal;(3) Department of Physics, University of Rome “La Sapienza”, P.le Aldo Moro 2, 00185 Rome, Italy |
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Abstract: | An analysis of drought in western Iran from 1966 to 2000 is presented using monthly precipitation data observed at 140 gauges uniformly distributed over the area. Drought conditions have been assessed by means of the Standardized Precipitation Index (SPI). To study the long-term drought variability the principal component analysis was applied to the SPI field computed on 12-month time scale. The analysis shows that applying an orthogonal rotation to the first two principal component patterns, two distinct sub-regions having different climatic variability may be identified. Results have been compared to those obtained for the large-scale using re-analysis data suggesting a satisfactory agreement. Furthermore, the extension of the large-scale analysis to a longer period (1948–2007) shows that the spatial patterns and the associated time variability of drought are subjected to noticeable changes. Finally, the relationship between hydrological droughts in the two sub-regions and El Niño Southern Oscillation events has been investigated finding that there is not clear evidence for a link between the two phenomena. |
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Keywords: | Drought variability Standardized precipitation index Principal component analysis ENSO events |
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