انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 20 3 2026 07 23 Regionalization, temporal-spatial characteristics, and trend of changes in precipitation and drought in Iran Regionalization, temporal-spatial characteristics, and trend of changes in precipitation and drought in Iran 205 240 227424 10.30499/ijg.2025.499798.1663 FA Peyman Mahmoudi Associate Professor, Department of Physical Geography, Faculty of Geography and Evironmental Planning, University of Sistan and Baluchestan, Zahedan, Iran 0000-0003-2138-0973 Abdolraoof Shahozei M.Sc., Department of Physical Geography, Faculty of Geography and Evironmental Planning, University of Sistan and Baluchestan, Zahedan, Iran Journal Article 2025 01 13 <span>This study regionalizes Iran's precipitation and analyzes the temporal-spatial behavior of precipitation and drought in Iran. It used two sets of precipitation data. The first data set is the monthly precipitation data of 63 synoptic stations and the second data set is the Gridded precipitation data of three databases: Global Precipitation Climatology Center (GPCC), Climatic Research Unit (CRU) of the University of East Anglia (UEA) of England and University of Delaware (UDel) of the United States. As the results showed, the GPCC Gridded precipitation data set with a very high correlation </span><span> </span><span><span> </span>with Iranian station data was recognized as the most suitable Gridded precipitation data set for Iran. Cluster analysis on this precipitation dataset showed Iran can fall under seven different precipitation regions. Various characteristics of droughts, such as intensity, duration, and frequency of each precipitation region, were extracted and analyzed through four standardized precipitation indices (SPI), percentage of normal precipitation (PNPI), precipitation variability (RVI), and deciles (DI). The results disclosed that the three precipitation regions of Southwest (SW), Central Iran (CI), and Northwest-Northeast (NW-NE), among the seven precipitation regions of Iran, are the most vulnerable precipitation regions to drought.</span><br><span> </span> <span>This study regionalizes Iran's precipitation and analyzes the temporal-spatial behavior of precipitation and drought in Iran. It used two sets of precipitation data. The first data set is the monthly precipitation data of 63 synoptic stations and the second data set is the Gridded precipitation data of three databases: Global Precipitation Climatology Center (GPCC), Climatic Research Unit (CRU) of the University of East Anglia (UEA) of England and University of Delaware (UDel) of the United States. As the results showed, the GPCC Gridded precipitation data set with a very high correlation </span><span> </span><span><span> </span>with Iranian station data was recognized as the most suitable Gridded precipitation data set for Iran. Cluster analysis on this precipitation dataset showed Iran can fall under seven different precipitation regions. Various characteristics of droughts, such as intensity, duration, and frequency of each precipitation region, were extracted and analyzed through four standardized precipitation indices (SPI), percentage of normal precipitation (PNPI), precipitation variability (RVI), and deciles (DI). The results disclosed that the three precipitation regions of Southwest (SW), Central Iran (CI), and Northwest-Northeast (NW-NE), among the seven precipitation regions of Iran, are the most vulnerable precipitation regions to drought.</span><br><span> </span> https://www.ijgeophysics.ir/article_227424_0786b040a26e4266e2f3bfb1826655c7.pdf