Space-time variability of extreme rainfall in the River Nile basin

In this study, spatio-temporal variability in daily rainfall extremes based on 0.5 degrees x0.5 degrees gridded data over the Nile basin was analysed using the quantile perturbation method. The co-occurrence of the extreme rainfall variability with the variation in the large-scale ocean-atmosphere conditions was also investigated. Based on a 15-year moving window, it was found that the extreme rainfall shows oscillatory behaviour over multi-decadal time scales. The latitudinal difference in the multi-decadal extreme rainfall oscillations divides the study area into the Northern, Central, and Southern regions. The variability in the extreme rainfall of the Central region is dominantly driven by the variation in the sea surface temperatures of the Atlantic and Pacific Oceans. For the Southern region, extreme rainfall variability is linked to the anomalies in the sea level pressure of the North Atlantic Ocean and the variation in the sea surface temperature of the Indian Ocean. The variation in the extreme rainfall of the Northern region corresponds to the anomalies in sea surface temperatures of the Indian and Atlantic Oceans as well as from the Pacific Ocean.