TITLE:
Analysis of Spatial-Temporal Characteristics of Extreme Precipitation during the Long Rainy Season over East Africa
AUTHORS:
Niyigena Thadee, Clara Liapapa, Sandrine Giramahoro, Ebaju Gerverse Kamukama
KEYWORDS:
Extreme Precipitation, Spatial-Temporal Variability, East Africa, Long Rainy Season (MAM)
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.4,
March
31,
2026
ABSTRACT: In recent decades, rainfall variability across East Africa has intensified, raising concerns regarding the spatial and temporal behavior of extreme precipitation during the long rainy season (March-May). This study analyzes the spatial-temporal characteristics of extreme precipitation over East Africa for the period 1979-2024 using daily precipitation from the ERA5 reanalysis at 0.25˚ resolution. Extreme events are defined using a percentile-based approach that identifies rainfall exceeding the local 90th percentile of wet days. The results reveal pronounced spatial heterogeneity in extreme-event frequency, with western and central sectors experiencing approximately 8 - 10 extreme days per season, while northeastern areas generally record fewer than 3 - 4 days. In contrast, extreme-event intensity exhibits more localized maxima, with median rainfall on extreme days typically ranging between 15 and 30 mm per day and isolated regions exceeding 40 - 60 mm per day. Interannual variability analysis shows that extreme precipitation during March-May is dominated by a coherent large-scale mode explaining roughly one-third of the total variance, indicating organized regional-scale atmospheric control. These findings demonstrate that long rainy season extremes are characterized by systematic spatial gradients, distinct frequency-intensity structures, and structured year-to-year variability. By separating event occurrence from rainfall magnitude and quantifying dominant variability patterns, this study provides an improved characterization of extreme precipitation dynamics during the long rainy season over East Africa.