CHIRPS ‐Based Multi‐Index Assessment of Precipitation Variability and Drought Dynamics in Sulaymaniyah Province, Kurdistan Region of Iraq (1981–2023)

ABSTRACT

The intensifying impacts of climate change on the spatial and temporal organization of precipitation increasingly threaten water security, agricultural productivity, and ecosystem integrity across the semi‐arid regions of the Middle East. Sulaymaniyah Province, situated in northeastern Iraq, exemplifies this vulnerability through its complex orography, steep precipitation gradients, and spatially heterogeneous drought regimes, all of which carry substantial socio‐economic consequences. This study presents a multi‐index spatiotemporal analysis of precipitation variability and drought dynamics across the province for the period 1981 to 2023. The methodological framework integrates the high‐resolution Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) dataset, temperature fields derived from TerraClimate, and observational records from 19 spatially distributed meteorological stations. Five complementary climatological indices were applied: the Precipitation Concentration Index (PCI), the Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the UNEP Aridity Index (AI). The spatial analysis reveals a pronounced southwest‐to‐northeast precipitation gradient, with mean annual values ranging from 297.7 mm at semi‐arid Kifri in the south to 938.5 mm at humid Penjwin in the northeast. The basin‐mean precipitation contracted from 657.9 (1981–2000) to 607.0 mm (2001–2023), a relative reduction of 7.7% that is reproduced at all 19 stations. This inter‐period shift in the mean is not, however, accompanied by a monotonic station‐level trend: the Wald‐Wolfowitz runs test failed to reject the null hypothesis of randomness at any individual station ( p  > 0.05), so the decline is expressed as a downward displacement of the precipitation distribution rather than as a deterministic trend. The 2007 to 2008 hydrological year recorded the provincial minimum at 350.56 mm, whereas 2018 to 2019 registered an exceptional maximum of 983.18 mm. The coefficient of variation averaged 22.85% across all stations, indicating moderate interannual variability; however, southern stations exhibited pronounced amplification during the second period, with Kifri (+18.5%), Kifri Bawanur (+16.0%), and Chamchamal (+14.5%) emerging as zones of accentuated drought vulnerability. The PCI analysis demonstrates that 79.6% of rainy seasons fell within the irregular to strongly irregular categories (PCI ≥ 16), and no station exhibited a uniform distribution (PCI < 10) in any season. The PCI analysis demonstrates that 79.1% of rainy seasons fell within the irregular to strongly irregular categories (PCI ≥ 16), and no station exhibited a uniform distribution (PCI < 10) in any season. SPI‐based classification indicates that 70.68% of seasons remained within the near‐normal range, whereas 8.4% qualified as moderate drought and 8.5% as severe drought, with extreme events concentrated at southern stations. Five major drought episodes were identified, the most acute being 2007 to 2009 (SPI minimum of −2.82 at Kalar) and the most protracted spanning 1988 to 1992. RDI _st mean values of −1.74 at Kifri and −1.61 at Kalar corroborate their classification as chronically drought‐affected zones. The SPEI‐12 series exhibits a statistically robust desiccating trend (Mann–Kendall τ ≈−0.49, p  < 0.001; Sen slope ≈ −0.024 units yr. ⁻¹ ), this being the only formally significant monotonic trend detected in the study and one that is reproduced at every station (station‐level τ between −0.30 and −0.42, all p  < 0.01). Between 2020 and 2023, 86% of station‐years fell within the combined drought categories. Collectively, these findings substantiate the imperative for spatially differentiated water governance, drought‐adaptive cropping calendars, and climate‐resilient agricultural policy at the provincial scale, while underscoring the wider relevance of such analyses for transboundary water security planning across the upper Tigris basin.