Hydroclimatic Variability and Drought Characterisation in Northern Togo, 1981-2025

Abstract Climate change is increasingly intensifying drought conditions across West Africa, with northern Togo emerging as one of the most drought-vulnerable sub-regions of the continent yet lacking locally adapted tools for effective droughts monitoring and moisture deficit assessment. This study analyses rainfall variability, drought frequency and moisture deficit across three agroecological zones of northern Togo from 1981 to 2025. Three synoptic stations were combined with NASA Prediction of Worldwide Energy Resources reanalysis and Climate Hazards Group InfraRed Precipitation with Stations satellite data. The Hamed-Rao modified Mann-Kendall test, Sen slope estimator and three change-point tests (Pettitt, Buishand, and Standard Normal Homogeneity Test) were applied to annual, seasonal and monthly timescales. The Standardized Precipitation Index, Standardized Precipitation-Evapotranspiration Index and Willmott-Feddema Moisture Index were calculated to evaluate drought conditions and moisture availability. No statistically significant precipitation trends were detected at any station, while a significant warming of +0.27 to +0.34 °C per decade amplified evapotranspiration demand. Consequently, the two drought indices have progressively diverged since 2003, a signal invisible when considering only precipitation, driven by a spatially coherent temperature change point identified around 2001-2003. All stations recorded exclusively negative Moisture Index values, confirming a permanent deficit of water in the entire area. Spatial analysis revealed predominantly positive moisture trends, with significant negative trends confined to fewer than 8% of grid cells. These findings emphasize the need for temperature-sensitive drought indices in early warning systems and provide critical insights for rain-fed cereal production and water resource management in one of West Africa's most climate-exposed regions.