application and evaluation of spi and spei indices in drought analysis

Objective: drought, recognized as one of the most severe natural disasters, is characterized by a prolonged deficiency in rainfall. this study aims to analyze drought patterns in the khorramabad region using the mann-kendall test. materials and methods: for this purpose, the standardized precipitation-evapotranspiration index (spei) and the standardized precipitation index (spi) were applied, utilizing average, minimum, and maximum precipitation and temperature data recorded at the khorramabad synoptic station from 1999 to 2022. results and discussion: the results of the drought analysis indicate the occurrence of various extreme events over the study period. the findings reveal a general increasing trend in drought severity, moving towards higher positive index values, suggesting a greater prevalence of wet years. however, temporal analysis of drought variations and the mann-kendall trend test indicate both positive and negative shifts throughout the study period. a negative and decreasing trend has occurred in both drought indices in the khorramabad region, which is not statistically significant at any level because spi z statistic is -0.8, and spei z statistic is -1.6, less than 1.96. these fluctuations may reflect localized climatic changes, highlighting the complexity of drought dynamics in the region. conclusions: this study underscores the necessity for continuous monitoring and adaptive water resource management strategies to mitigate the impacts of climate variability in khorramabad. drought, recognized as one of the most severe natural disasters, is characterized by a prolonged deficiency in rainfall. this study aims to analyze drought patterns in the khorramabad region using the mann-kendall test. for this purpose, the standardized precipitation-evapotranspiration index (spei) and the standardized precipitation index (spi) were applied, utilizing average, minimum, and maximum precipitation and temperature data recorded at the khorramabad synoptic station from 1999 to 2022. the results of the drought analysis indicate the occurrence of various extreme events over the study period. the findings reveal a general increasing trend in drought severity, moving towards higher positive index values, suggesting a greater prevalence of wet years. however, temporal analysis of drought variations and the mann-kendall trend test indicate both positive and negative shifts throughout the study period. a negative and decreasing trend has occurred in both drought indices in the khorramabad region, which is not statistically significant at any level because spi z statistic is -0.8, and spei z statistic is -1.6 which is less than 1.96. these fluctuations may reflect localized climatic changes, highlighting the complexity of drought dynamics in the region. this study underscores the necessity for continuous monitoring and adaptive water resource management strategies to mitigate the impacts of climate variability in khorramabad.