Drying In The Congo River Basin: Attribution From Atmospheric Moisture Transport
Date:
Recommended citation: Stojanovic, M., Beltrán-Fonsec, B., Sorí, R., Pérez-Alarcón, A., Nieto, R., Gimeno, L. (2026). Drying In The Congo River Basin: Attribution From Atmospheric Moisture Transport. XL Reunión Bienal de la Real Sociedad Española de Física . Sevilla, 20-24 July 2026, pp287 https://bienalfisicasevilla2026.es/static/upload/ow222/events/ev784/Site/files/Libro_de_Abstracts_Bienal_2026-05.pdf
#Abstract
The Congo River Basin, located in central-equatorial Africa, is one of the most important hydroclimatic regions, encompassing major river systems and extensive tropical forests. It is also one of the key rainfall regions in the tropics, supporting ecosystems, river discharge, and millions of people. In this study, we identify an area within the basin that has experienced a marked drying trend during the 1981–2023 period. For this region, we used global outputs from the Lagrangian model FLEXPART to diagnose the main moisture sources contributing to precipitation. Our results show that precipitation over the target region has decreased and potential evapotranspiration has increased, explaining the aridification trend. The Lagrangian analysis reveals that precipitation over the Congo River Basin is supplied by three oceanic moisture sources: the Atlantic Ocean, the Indian Ocean, and the Red Sea and three continental sources: local recycling within the study region, the surrounding Congo region, and external terrestrial areas. Moisture-source diagnostics indicate that local recycling and the rest of the Congo basin dominate the climatological moisture supply, making terrestrial sources the major responsible for supplying moisture. However, the trend analysis reveals a weakening in the absolute contribution of moisture to precipitation from all sources, while relative trends show that locally recycled moisture inputs decline less rapidly than the rest. A Ridge-based trend attribution suggests that the observed negative precipitation trend is more strongly associated with weakening oceanic moisture contributions than with changes in continental sources, although the surrounding Congo region emerges as the leading individual contributor. Additional analysis of vertically integrated moisture flux divergence further indicates that the drying hotspot lies within a climatologically convergent moisture regime that has weakened over time, consistent with increasingly unfavourable atmospheric conditions for rainfall.