Comparison of precipitation-based drought indices: Drought assessment and monitoring in a TR82 region in Türkiye

Drought is a multifaceted natural hazard with profound impacts on water resources, agriculture, ecosystems, and socio-economic systems. This study investigates meteorological drought in the TR82 Region of northern T & uuml;rkiye, analysing precipitation data from ten meteorological stations spanning 1981-2023. Three precipitation-based drought indices-the Standardized Precipitation Index (SPI), China-Z Index (CZI), and Z-Score Index (ZSI)- were applied to assess drought characteristics, including frequency, severity, and spatial variability. Analysis revealed recurrent drought periods in 1981-1982, 1985-1986, 1989, 1992-1994, 1996, 2003-2004, 2006-2008, 2013, 2017, 2020, and 2022, indicating that drought occurrence in the region is neither sporadic nor isolated. Moderately dry and wet conditions were more frequent than extreme events, while prolonged droughts after 2000 suggest increasing persistence and intensification. Correlation analysis demonstrated very strong agreement among the indices, with mean correlation coefficients of 0.9956 (SPI-ZSI), 0.9953 (SPI-CZI), and 0.9943 (ZSI-CZI), confirming ZSI as a viable alternative to SPI for regional drought monitoring. In addition, the results are consistent with the presence of scale-invariant, nonlinear dynamics in precipitation variability, as indicated by observed power-law behavior and the framework of self-organized criticality (SOC) in rainfall systems, suggesting that short-term fluctuations are statistically related to longer-term patterns. The use of precipitationbased drought indices showed that the driest years align with the years of lowest annual precipitation, and similar correspondence is observed for wet years. These findings provide robust evidence of the TR82 Region's vulnerability to drought and underscore the importance of multi-index approaches and consideration of nonlinear climate dynamics for effective drought assessment and proactive water resource management.