Testing seasonal persistence of rainfall in arid and semi-arid african climatic zones using a seasonal fractional model

Abstract Arid and semi-arid regions of Africa are characterised by low mean annual rainfall with substantial temporal variability due to factors influencing climate in the region, coupled with hot temperatures in the Sahara region. This study therefore investigates seasonal persistence in the amount of rainfall in 17 African countries that are prone to aridity. For this purpose, we use a time series econometrics framework that is based on the concept of seasonal fractional integration, extending the seasonal unit root methods to the fractional case. Monthly data from January 1901 to December 2024 are used, and the results indicate fractional degrees of integration in the interval (0, 1) in all countries, with some of them showing a stationary pattern (0 < d < 0.5) while others showing nonstationarity (d ≥ 0.5). The lowest degrees of persistence are found in several northern (Algeria, Tunisia) and eastern (Somalia, Kenya) countries, and a time trend is found to be significantly positive in a number of cases, being the highest for Ethiopia and Kenya. Results emanating from this study has important implications for drought and occasional flash floods management in the arid and semi-arid regions for ecosystems and human lives that depend majorly on rain-fed activities.