Investigation The Cause of Drought Condition Over Afghanistan With Consideration Of Climate Trends And Indices

Global warming significantly intensifies drought conditions, posing severe threats to vulnerable, agriculturally dependent nations like Afghanistan. Existing research often lacks a systematic framework for selecting and validating representative extreme climate indices (ECIs) to accurately capture regional hydroclimatic variability in data-scarce environments. This study addresses this gap by investigating the relationship between drought severity and extreme temperature and precipitation events across Afghanistan during the period 1975–2014. Methodologically, twenty-seven ETCCDI-defined ECIs were initially examined. A robust subset of eight representative indices was systematically selected through correlation analysis and Variance Inflation Factor (VIF) diagnostics, ensuring VIF values below 2.0 to minimize multicollinearity. The Standardized Precipitation Evapotranspiration Index (SPEI), derived from ERA5 reanalysis data, characterized drought. The Mann–Kendall test and Sen’s slope estimator were applied to determine the statistical significance (P < 0.05) and magnitude of long-term trends, followed by correlation analysis. Results indicate that temperature-related ECIs exhibit consistent and statistically significant upward trends across Afghanistan, with TX90P and TN90P increasing by 2-4% per decade. These temperature indices showed strong negative correlations with SPEI, ranging from approximately -0.5 to -0.65, directly linking rising temperatures to intensified drought. The SPEI itself revealed a statistically significant decreasing trend (P < 0.05), notably shifting from near-zero values pre-1999 to consistently below -1 for lower elevations post-1999. Conversely, precipitation-related ECIs displayed no significant long-term variation and exhibited only weak, inconsistent correlations with SPEI (0.0 to 0.25), confirming their lesser role. These findings underscore the dominant influence of temperature extremes on Afghanistan's drought development.