Investigating Temporal Trends and Spatial Characteristics of Rainfall and Meteorological Drought in the West of Iran during the Last Few Decades

Abstract

Drought is one of the most serious problems arising for human societies and ecosystems from climate<br />variability. This phenomenon causes billions of dollars in global damages annually and affects more<br />people than any other form of natural disasters.<br />In this study, the trends of rainfall and meteorological drought time series were investigated at ten<br />stations located in the east of Iran for the period of 1966–2005. Amounts of drought severity were<br />computed using standard precipitation index (SPI) for a 12-month time scale. The trend analyses of the<br />data were also performed using the Mann–Kendall test and the Sen's slope estimator. The results of<br />this study showed that the rainfall and drought data had high variations to average values in the study<br />period, and these variations increased with increasing aridity towards the east of the study area. The<br />results of the trend tests revealed statistically significant decreasing trends in the rainfall time series of<br />Sar-Pol-Zohab, Bijar, Sanandaj and Saghez stations at the rates of 7.99, 6.68, 5.51 and 5.03 mm/year,<br />respectively. Furthermore, drought severity significantly increased at Kermanshah, Saghez, Sanandaj<br />and Khorram-Abad stations during the last four decades. The results indicated that all of the stations<br />experienced at least one extreme drought during the study period.