Statistical Assessment of the Extreme Rainfall Event of 2024 in Maradi and Zinder of South-Eastern Niger

Abstract

Since the severe droughts of the 1970s, the Sahel, and Niger in particular, has faced a new precipitation regime. Although cumulative rainfall is improving, this recovery is accompanied by a resurgence of extreme weather events, such as torrential rains. The latter leads to recurring floods with devastating socio-economic consequences for local populations. This study aims at analyzing the specific nature of the 2024 rainy season in south-eastern Niger (Maradi and Zinder) to determine whether it constitutes a climatic anomaly over the last three decades. The analysis is based on NASA data from the 1991–2024 period. Three statistical tools were employed: the Standardized Precipitation Index (SPI) to characterize the moisture levels of each year, interannual variability to compare annual totals versus the 1991–2020 climate normal, and the Gumbel distribution to estimate the probability of occurrence and the rarity of the event. The results show that nearly the entire study area significantly exceeded the climate average of 281 mm. SPI values between 0.5 and 2 confirm a year ranging from moderately to extremely wet. With a record 560 mm, the year 2024 surpassed the previous extreme of 2020 (519 mm) within the 1991–2020 period, with a probability of exceedance of 0.41%. Thus, 2024 stands out as an exceptional event on the scale of recent decades. This study demonstrates that the 2024 season is a "breakout" year due to its extreme nature. The concentration of such events in the recent period (2020 and 2024) reflects a profound mutation of the climate in south-eastern Niger.