Long-term analysis of the spatiotemporal standardized precipitation evapotranspiration index for West Asia

Droughts are one of the most catastrophic environmental hazards that have historically led to the destruction of many ancient civilizations in the cradle of civilization in the West Asian region. The purpose of this study is to analyze the long-term temporal and spatial variability of extreme long-term drought intensities of 18 to 48 months in the West Asian region in the statistical period of 118 years (1901–2018). In this study, using standardized precipitation evapotranspiration index (SPEI) and accurate gridded data, the critical grid points (CGPs) caused by extensive and severe droughts in West Asia in the 118-year long-term period (1901–2018) was analyzed. The results of the cumulative standardized precipitation evapotranspiration index (CSPEI) showed that in the long-term timescales of SPEI-18, SPEI-24, SPEI-36, and SPEI-48 months, the most affected areas of severe drought or the drought CGPs of West Asia were located in Yemen, Southern Iran, and western Saudi Arabia. The Southern and Western regions of Turkey, Northwestern Turkmenistan, Western Pakistan, and Afghanistan, as well as Western Oman and Azerbaijan, have also been less impacted by severe and widespread droughts in West Asia. Moreover, Armenia was found to experience fewer severe droughts than other study areas. The trend of temporal changes in the CGPs derived from the severity and extent of droughts indicates a significant downward trend in the CGPs of droughts in West Asia, which points to the fact that severe and widespread droughts will continue in the future and are likely to intensify. In other words, in the future, investigators will see more widespread and more severe droughts in the West Asian region, especially in Yemen, Iran, Saudi Arabia, and Iraq.