Multi-index assessment of meteorological drought in Türkiye based on CHIRPS and TRMM data

Drought is one of the most critical environmental challenges, particularly in regions with high climatic variability such as Türkiye. This paper examines the spatiotemporal patterns of meteorological drought in Türkiye within a multi-index framework. In this regard, three precipitation-based indices, including the Precipitation Concentration Index (PCI), Rainfall Anomaly Index (RAI), and Percent of Normal Precipitation Index (PNPI), were obtained using the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and The Tropical Rainfall Measuring Mission (TRMM) data between 1998 and 2019. The results show a high level of spatial heterogeneity in precipitation distribution. The spatial PNPI analysis revealed a pronounced contrast between 2008 and 2018. In 2008, severe drought (PNPI <75) and drought (PNPI 75–89) conditions covered 38.3% and 47.8% of Türkiye, respectively, indicating that approximately 86.1% of the country experienced drought or severe drought conditions. In contrast, in 2018, Wet (PNPI 110–124) and very wet (PNPI ≥125) conditions covered 41.1% and 37.5% of Türkiye, respectively, indicating that approximately 78.6% of the country experienced wet or very wet conditions. The year 2008 was identified as an extreme drought year, with minimum PNPI values reaching about 47% and RAI values reaching −2.70, whereas 2018 represented a predominantly wet year at the spatial scale, with maximum PNPI values reaching 174% and RAI values exceeding +3.36. Satellite datasets were shown to be greatly enhanced by bias correction when compared with ground-based observations. CHIRPS showed superior accuracy ( R = 0.990; RMSE = 4.13 mm/month) compared to TRMM ( R = 0.963; RMSE = 7.89 mm/month). The findings indicate that combining multiple precipitation indices with satellite-based precipitation datasets can provide spatially explicit information to support drought surveillance and climate-informed decision making. The approach has potential applications for prioritizing drought monitoring, preparedness, water-resource planning, and subsequent regional or seasonal assessments, although these operational applications were not directly evaluated in this study.