Abstract
Available water resources in the Middle East, as one of the most water-scarce regions of the world, have undergone extra pressure due to climatic change, population growth, and economic development during the past decades. The objective of this study is to detect the trends and quantify the changes in aridity with respect to precipitation and potential evapotranspiration in 20 countries of the Middle East and the adjacent area. A pixel-wise trend analysis was conducted on precipitation, potential evapotranspiration, and the aridity index for 71 years from 1948 to 2018. Results showed a statistically significant (|Z| > 1.96) increase up to 106% in aridity (a downward trend in the aridity index) from December to September in most parts of the region. Aridity in October and November had a downward tendency in most parts of the study area. At an annual time scale, 62.5% of the detected trends in aridity were found to be upward (up to 96% increase) due to the combined effects of the decrease in precipitation and the increase in potential evapotranspiration. Annual aridity was found to be downward in 37.5% of the detected trends (up to 61% decrease). The highest and the lowest trends in aridity were found in the north of Sudan (96%) and eastern Arabia (- 61%).