A comparison of the 2023/24 El Niño with other El Niño events during 1981—2024 over the Okavango River Basin, southern Africa

Abstract

Abstract The early 2024 drought in southern Africa, which was worsened by an El Niño, caused serious grain shortages in the region. We analyse rainfall and circulation anomalies for the 2023/24 El Niño and compare them with those for the other El Niño events during 1981–2024 over the Okavango River Basin (ORB), southern Africa. Attention is also paid to the north catchment of the ORB and to Ngamiland district in northwestern Botswana, which contains the Okavango Delta, world-famous for its highly biodiverse ecosystems. Focus is placed on the wettest months (December-February (DJF)) in the region. Due to data sparsity, the Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) is used for rainfall analysis. It is found that DJF rainfall totals associated with the 2023/24 El Niño minus the totals associated with the other El Niño events are generally negative mainly over the north catchment. 2023/24 minus 2009/10 DJF rainfall totals show the most extensive negative values over the north catchment, Ngamiland and the adjoining regions. However, 2023/24 minus 2018/19 DJF rainfall totals are positive over most of the north catchment and Ngamiland, contrary to the strengths of the 2023/24 (substantially stronger) and 2018/19 (substantially weaker) El Niño events. Circulation anomalies for the two El Niño events can help explain these anomalies since, for example, they show that more moisture was advected from the equatorial Atlantic Ocean towards the ORB in DJF 2023/24 than in DJF 2018/19. These findings may help guide policy development for better management of resources.