A PCA-based composite drought index integrating meteorological and vegetation indicators in the North-Eastern Dry Zone of Karnataka, India

Drought is a recurring climatic hazard in the North-Eastern Dry Zone (NEDZ) of Karnataka, affecting agriculture and water-resource availability. This study analysed the spatio-temporal variability of drought and wet conditions during 2000–2024 using daily meteorological observations from KSNDMC and IMD and MODIS MOD13Q1 vegetation data. A Composite Drought Index (CDI) was developed by integrating the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Normalized Difference Vegetation Index (NDVI), and Vegetation Condition Index (VCI), with indicator weights derived through Principal Component Analysis (PCA). Temporal drought profiles were evaluated for 11 stations, together with a combined station year spatio-temporal assessment. Three broad drought phases were identified during 2001–2004, 2009–2013, and 2016–2019, whereas 2020–2022 represented a prominent wet phase across several stations. During major drought years, severe-to-extreme drought affected more than 90% of the months at several locations, while Above Normal conditions reached 100% at selected stations during 2020–2022. The PCA-derived weights showed broadly balanced contributions from meteorological and vegetation indicators, indicating that the CDI represented both climatic water deficit and vegetation response. The major drought and wet periods also showed temporal correspondence with KSNDMC information and independent published drought assessments for Karnataka. Overall, the PCA-based CDI provides an integrated framework for characterizing station-level drought variability and supporting drought preparedness and water-resource planning in semi-arid Karnataka.