Diakaria Diallo^{1, 2}, Moussa Mamady Traore^{1, 3,}, Tamba Nicolas Millimono^{2, 4}, Mamadou Bailo Barry⁵, Ibrahima Kalil Kanté^{2, 6}, Mamadou Keita⁷, Hambaliou Balde², Bakary Traore⁸, Abdoulaye Baniré Diallo⁹, Maoro Beavogui¹⁰, Idrissa Diaby²

Rainfall variability in West Africa represents a major scientific issue due to its direct impacts on water resources, agriculture, and socio-economic systems. In Guinea, a country highly dependent on precipitation regimes, recent observations suggest a non-stationary evolution of the climate, characterized by alternating wet and dry phases as well as potential changes in rainfall patterns. In this context, the study aims to analyze the spatio-temporal variability of annual precipitation between 1986 and 2015 in order to identify and characterize the main climatic breakpoints across the Guinean territory. The study is based on high spatial resolution CHIRPS v2.0 satellite data (0.05°), aggregated into annual totals and then standardized using the Standardized Precipitation Index (SPI). The statistical analysis combines several complementary non-parametric change-point detection methods, including the Pettitt test, the Lee & Heghinian test, and Hubert segmentation, applied across the four natural regions of Guinea. This approach makes it possible to identify discontinuities in rainfall time series, assess their significance, and compare their spatial distribution according to regional climatic gradients. The results highlight strong interannual rainfall variability and the existence of a major climatic shift beginning in the mid-1990s, reflecting a reorganization of the rainfall regime. A second phase of change, observed between 1999 and 2015, reveals an asynchronous and spatially heterogeneous dynamic, with contrasting behaviors across the natural regions. Overall, an increase in interannual variability and an intensification of hydroclimatic extremes is observed. In conclusion, the Guinean climate appears to have undergone a profound restructuring, characterized by increasing instability of the precipitation system, underscoring the need to integrate these breakpoints into adaptation strategies and water resource management planning

Rainfall variability, Climate change, Spatio-temporal analysis, Change-point detection, Guinea