TITLE:
Spatiotemporal Variability and Trends of East African Rainfall and Their Linkages to Large-Scale Oceanic Teleconnections
AUTHORS:
Gentil Samuel Ishimwe, Niyigena Thadee, Sseruwagi David Daniel, Giramahoro Sandrine, Musabyimana Jean De La Croix, Abiyu Muse Abayneh
KEYWORDS:
East Africa, Rainfall Variability, Climate Trends, SST Teleconnections, ENSO, Indian Ocean Dipole, ERA5, EOF Analysis
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.5,
May
28,
2026
ABSTRACT: Rainfall variability is a critical component of climate dynamics in East Africa, where socio-economic systems are highly sensitive to precipitation fluctuations. This study investigates the spatiotemporal variability of rainfall and its relationship with large-scale ocean-atmosphere drivers over Rwanda, Uganda, Kenya, Tanzania, and Burundi using ERA5 reanalysis data and sea surface temperature (SST). Statistical methods including standardized anomalies, Mann-Kendall trend analysis, empirical orthogonal functions (EOF), and correlation analysis, were applied to quantify variability, detect trends, and identify dominant climatic controls. Results reveal a pronounced west-east rainfall gradient, with maximum rainfall over the Lake Victoria basin and western highlands, and lower totals toward eastern Kenya and northeastern Tanzania. Trend analysis indicates declining annual and MAM rainfall over the western sector, while OND trends are spatially heterogeneous, with localized increases in eastern regions. Rainfall anomalies show strong interannual variability, with significant dry conditions during the early 2000s and wet events in the late 1990s and late 2010s. EOF analysis indicates that rainfall variability is dominated by a coherent regional mode explaining 42.2% (MAM) and 61.3% (OND) of total variance, with secondary modes reflecting spatial contrasts. Correlation results demonstrate stronger SST-rainfall relationships during OND, particularly over the equatorial Pacific and western Indian Ocean, compared to weaker MAM connections. These findings highlight the combined influence of regional and large-scale climatic drivers and provide a scientific basis for improving seasonal forecasting and climate risk management in East Africa.